Penn State's flower trial garden in Lancaster County.

    I’m all for saving money, but this is one area where you really do get what you pay for.

   A few of those cheapo 99-cent packs of flowers might do halfway decent in a pot, but most of the time they just don’t perform nearly as well as the named and more expensive flower varieties sold at greenhouses and garden centers.

   The difference is genetics. The cheapie plants tend to be older varieties grown from inexpensive seed. The high-performers (generally) are carefully bred, selected and tested varieties that are started from cuttings from mother plants.

   In my own gardens, the difference has been striking enough that I no longer buy those box-store “bargains.” I admit, I cringe at paying some of the prices these superior varieties cost, but I also know how much better they’re going to look come summer.

   If you’re not convinced, take a trip down to Penn State’s trial gardens near Landisville, Lancaster County.

   Every year, Penn State test-grows hundreds of new and newish varieties and rates them to help guide the market toward the best quality.

   You can see the trials yourself at no charge. It’s an excellent place to take notes on what flowers you’d like to try in your own yard.

   What’s more, Penn State posts photos and ratings of past trials online so you can research varieties before shelling out your hard-earned money.

   For ratings and directions, check out this site: http://www.trialgardenspsu.com.

   A few specific annuals that I think are some of the best on the market:

   Petunias. So many of the new ones are light years ahead of Grandma’s straggly varieties. My favorite is ‘Supertunia Vista Bubble Gum,’ a neon rosy-pink bloomer. But you’ll do fine with any of these series: ‘Supertunia,’ ‘Surfinia,’ ‘Sanguna,’ ‘Wave,’ ‘Famous’ and ‘Suncatcher.’

   Angelonia.These remind me of little orchids. ‘Serena’ is compact and seed-grown, so they should be affordable in 6-packs. I don’t know why every garden center isn’t selling these. ‘Angel Wing,’ ‘Carita’ and ‘Alonia’ also are very good.

Angelonia and petunias.

    Zinnias. The ‘Profusion’ series is seed-grown and less expensive. ‘Profusion Cherry’ fades, but ‘Orange’ and ‘Fire’ are excellent. ‘Zowie Yellow Flame’ is a traffic-stopper. And the ‘Zahara’ series also is excellent, compact and disease-resistant.

   Euphorbia. The annual type of this genus grows into a ball of white babys-breath-like flowers. They’re trouble-free, long-blooming and don’t get eaten by animals. ‘Diamond Frost’ is best known, but ‘Hip Hop’ and ‘Breathless’ are very similar.

   Coleus. Almost hard to go wrong if you stay away from the 99-cent 4-packs. Most of the varieties in 4-inch pots are big, beautiful, bullet-proof and more sun-tolerant than yesteryear’s types.

   Impatiens. Also hard to go wrong here. Even the cheapie ones do reasonably well. Impatiens are our No. 1 shade annual for good reason. Check out the new ‘Sunpatiens’ series for a high-performing, sun-tolerant series.

   Begonias. ‘Bonfire’ and ‘Dragon Wing’ are two of the biggest, showiest types. They’re best in pots and baskets but also perform well in the ground (sun or shade). Most of the wax types also are fine, although they don’t spread very far or very fast.

   Blue salvia.Tough in heat, sun and drought, and the rabbits don’t bother them. Their spiky blue-purple flowers look nice with pink petunias. Try ‘Signum,’ ‘Victoria’ or ‘Rhea.’

Verbena 'Magalena Pink Swirl.'

    Verbena. Big difference in variety here. The seed-grown ‘Quartz’ and ‘Obsession’ series always die for me. Much better are ‘Temari,’ ‘Aztec,’ ‘Lanai,’ ‘Fuega,’ ‘Magalena’ and ‘Tukana,’ although all sometimes go out of flower in summer heat.

   Vinca. These like warmth, so don’t plant too soon. The best performers I’ve seen are the ‘Cora,’ ‘Jaio,’ ‘Nirvana’ and ‘Pacifica’ series, although I also like ‘Blue Pearl’ and ‘First Kiss Blueberry.’

   Rudbeckia. One of the brightest, most eye-grabbing flowers of any kind is ‘Tiger Eye Gold.’ The flowers are big, and the petals are neon gold. It’s slow to get going, but from mid-summer on, this one will be the star of your garden.

   Don’t ask me where to buy all of these. I can’t keep track of who has what at any given time, so I basically haunt all of my favorite places, scooping up the best of what I find at each.

   In the end, I’ve got a nice collection of flowers and some satisfaction at knowing I’ve helped a variety of local businesses (not to mention my credit-card company).

Shear a juniper back into bare wood and it'll stay bare, as has happened to the bottom of this poor juniper.

    Despite what you may see even at the hands of pros, not all plants take kindly to shearing. This kind of cutting can destroy the natural form of archers and weepers and cause weak, stubby growth on others.

   But even for chop-amenable species, there’s a right way and a wrong way to hedge.

   I sat in on a program on this by Roger Davis at last year’s Woody Plant Conference at Scott Arboretum. Davis prunes the amazing topiary yews at Longwood Gardens.

   His top bit of advice is to start young and keep at it regularly.

   “Hedge maintenance begins on Day 1,” says Davis. “It’s a training process, not something you do 20 years down the road. Don’t wait until the hedge is halfway over the walkway to start pruning. Hedges are like children. You have to start early.”

   If you whack back into bare wood, some species (like yew, hemlocks, hollies, privet and boxwoods) will push out new growth — although they’ll look butchered for awhile.

   Do that to others (fir, juniper, spruce and arborvitae, for example), and you’ll permanently deform them — or worse.

   Davis advises cutting back only enough to remove the new growth, or nearly so.

   For bigger-leafed evergreens (cherry laurel or rhododendrons, for example) or if you like a somewhat informal look, use pruners. The job will take a lot longer, but you’ll do less leaf damage.

    For that formal, sculpted look, use shears — power ones or old-fashioned hand-operated ones.

   Davis uses a 3-step shearing plan.

   Step 1 is a rough cut to get rid of new growth.

   Step 2 is a slow cut to even out bumps and divots.

   Step 3 is a smooth finish cut.

   “Take it nice and slow,” he says. “It takes longer this way, but you get a better result in the end.”

   Whatever tool you use, keep it sharp. Clean snips heal better and brown less.

Shear to a vase shape and your hedges will get bare at the bottom as the top foliage shades the lower.

    Remember, the idea is to cut the foliage, not to tear or rip it off.

   Also very important to keep any evergreen hedge from getting bare at the bottom — taper it out so the bottom is wider than the top, not vice versa as so many chainsaw-toters do.

   A vase shape causes the top to shade the bottom branches, and that’s why the bottoms get bare.

   Davis suggests a taper that goes out 1 to 2 inches for every foot of height.

   And one other trick for keeping a hedge dense and healthy — open up a few holes to let sunlight into the plant.

   For taller hedges, Davis cuts a few evenly spaced holes in the top. No one sees them anyway.

   All hedges also should get a few small openings at regular intervals in the sides to let in light that encourages more interior growth.

   “Openings let the snow fall through, too, and so you get less winter damage,” Davis adds.

   Most of your serious hedge-pruning should be done in spring with one or two neatening cuts in summer.

   Knock it off by late summer, and let your hedges get ready to go into dormancy in fall.

You might as well max out your production if you're going to dig up the ground.

If you’re going to go to the trouble of digging up ground to grow your own food, you might as well make the most of it.

I’ve been aiming to get the most food out of the least space with the least work for 30 years. Here are my top 10 ways:

   1.) Raised Beds

Hardly anyone has good soil, so forget just stripping off the grass and planting.

Pick a sunny spot and mark off the areas you want to plant. Then loosen the soil (at least 6 inches) and add enough compost or similar organic matter so the beds end up 4 to 6 inches above grade.

Most people build boxes to contain the soil. Stone, blocks, brick, recycled plastic timbers and rot-resistant wood are options. Or you can just mound up the beds without any edging.

The loose, raised beds give you good drainage and allow veggie roots to spread with impunity.

   2.) Improve the Soil

Vegetables yield best in quality soil – not the compacted clay, shale or rocky subsoil that’s likely lurking in your yard.

Work at least 1 to 2 inches of compost, peat moss, rotted leaves, mushroom soil or similar organic matter into your loosened “soil.”

Then buy a do-it-yourself, mail-in Penn State soil test kit (available for $9-$10 at county Extension offices, most garden centers or online at www.aasl.psu.edu/SSFT.HTM) to see what kind of fertilizer to add.

The test also will tell whether to add sulfur or lime to correct the soil’s acid level (pH) for optimal production.

   3.) Best Paybackers

Some veggies are worth more than others or yield best for the time and effort. Lean toward ones that give you the most bang for your buck (assuming you like to eat them).

Tops on my list for best value: tomatoes, peppers, cucumbers, asparagus, the whole onion family (including leeks, shallots and garlic), lettuce, squash, rhubarb, beans and snow peas.

   4.) Best Varieties

Some particular varieties of each crop yield better, taste better or fight off bugs and disease better than others.

Skip inferior, cheapie types and keep experimenting until you find the ones that do best in your garden. Variety matters. Pay attention to those names.

A recommended list from Cornell University and my own experience is posted at http://georgeweigel.net/favorite-past-garden-columns/edibles/variety-matters.

Planting the vegetable garden isn’t just a May thing. You can milk out weeks and even months of extra production by planting cool-season crops (peas, onions, lettuce, etc.) as early as March and by replanting a fall cool-season crop.

Plant protectors such as floating row covers, clear plastic domes and even milk jugs can help on those really cold nights.

A highly productive vegetable garden has no empty space during the growing season. Plant continuously. As one crop is harvested, fill the space with something seasonally appropriate.

Example: plant radishes in March, then peppers in May when the radishes are pulled, then leaf lettuce when the first frost kills the peppers.

   6.) Plant Closely

That loose, rich soil will let you space plants closer than the packs say.

More importantly, plant in blocks instead of rows. Raised beds don’t waste space because you’ll be picking, working and walking around the perimeter – especially when you keep the bed widths to 4 feet wide.

No need to allow for wasted row space. Plant a block of peppers 15 inches apart from one another or beans 3 inches apart in all directions.

A good spacing guide is Mel Bartholomew’s Square Foot Gardening system and book. See http://www.squarefootgardening.com/ or “The All New Square Foot Gardening” (Cool Springs Press, 2006, $19.99).

No reason why you shouldn’t grow vining and climbing plants up a trellis, cage or similar support.

You’ll get way more cucumbers and melons this way instead of letting them sprawl along the ground. Pole beans, pole peas, pumpkins, gourds and malabar spinach are other vertical options.

I eked out an extra crop of peas and beans by erecting a bamboo tripod (actually a quadripod) over top of my rhubarb patch. I picked beans while the rhubarb grew happily below.

   8.) Consistent Water

Water is the magic ingredient. Keep the soil consistently damp (but never soggy) to keep those roots growing and the plants producing at maximum level.

   9.) Control Weeds

Weeds compete for nutrients and moisture in the garden. Yank them as soon as any emerge.

Better yet, put down a light layer of chopped leaves or straw between the plants to discourage weeds as well as conserve moisture.

   10.) Control Animals

Assorted animals (especially deer, rabbits, groundhogs and voles) love your vegetables as much as you do. Deer and groundhogs especially can decimate an entire garden in just one night.

Figure on fencing the garden right off the bat. What’s worked best for me is sinking a 6-inch board the whole way around to discourage burrowing, then erecting a 3-foot, narrow-opening fence that’s left unsecured at the top (so groundhogs lack support to climb over).

Whole books have been written on keeping animals out of the garden with options including repellents, electric fencing, traps, scare devices, ill-tempered pets and more.

For ideas, see my Pennlive blog at http://blog.pennlive.com/gardening/index.html and select the “Animal Problems” button in the menu at left.

One of the disappointly sparse flower beds at Floriade 2012.

    Floriade 2012 was worth a look, but to be honest, I didn’t think it was nearly as impressive as the last one in 2002.

   This show had a distinctly more commercial flavor. Maybe I’m biased because I see through rose-colored lenses rather than dollar-bill-green ones, but in my mind, this Floriade doesn’t quite measure up with other world-class garden-tourism events such as the U.K.’s Chelsea Flower Show or our own Philadelphia International Flower Show.

   Most of our hardy band of 37 travelers thought the same thing. Everyone’s jaws dropped when we visited the 79-acre Keukenhof bulb garden near Lisse, but I got mostly lukewarm feedback when I asked their opinions on Floriade.

   Most of us were expecting to see more gardens, more plant variety and a lot less selling of Asian jewelry, wooden bowls and packs of Dutch clog-shaped slippers.

   The previous 2002 Floriade, held near the Dutch Schiphol Airport, struck me as a sort of Olympics of gardening with countries around the world building gardens to give visitors a flavor of horticulture in their homelands.

   Back then, the Dutch themselves folded numerous Keukenhof-caliber beds throughout the site, spelling out whole words in bulbs in one memorable football-field-sized display.

   For this Floriade, taking place in the southeastern Venlo region near the German border, only a few of the participating countries built gardens. Other than China, Indonesia and Turkey, most set up what amounted to sales booths.

   The U.S. didn’t take part at all.

   Plant-wise, what struck me first was underplanted display gardens, too much bare soil, exposed soaker hoses and even some weeds.

   Many of the plants — especially roses and deciduous trees — were barely leafed out. The bulb displays were just OK — a bit of a letdown to anyone visiting Floriade after seeing what’s possible at Keukenhof or even Longwood Gardens and Hershey Gardens, for that matter.

Floriade 2012 has relative few large bulb displays like this as compared to the last show.

    Yeah, it’s challenging to have everything looking great from opening day April 5 straight on through to fall.

   But given sufficient planning and investment, it’s not impossible.

   Roses, for example, can be speeded along in a greenhouse before being hardened off and set out closer to show time. Row covers can be used if cold nights threaten. Or at the very least, early bulbs can be interplanted to fill the barren space until the roses develop.

   More bulbs and cold-hardy annuals such as pansies, dusty miller and snapdragons would have helped add more color to the bare space between the perennials that will hit their prime in summer.

   Just some tighter spacing alone would have helped. In the case of a show like this, plants need to be packed way closer than in a garden being planned for future growth. The Philadelphia Flower Show is a perfect example of how show gardens can look lush and finished right off the bat.

   Hopefully, the show plans to add massive amounts of warm-weather annuals to beds that are now primarily bulbs or early-spring perennials.

   People traveling halfway around the world to see a world-class garden event don’t want to be told, “Just wait until you see this garden next month!” or “You should have seen what the bulbs looked like last month before we yanked them.”

   I recall hearing a lot of “oohs,” “aahs” and “wows” when I was walking around Floriade 2002. This time, I overheard visitors saying things like, “Well, I guess they have a right to make money by selling things,” and “There are just a bunch of pictures on the wall in there.”

   It seemed to me there’s more of an effort to make Floriade 2012 profitable, both for the participants and the sponsors/organizers (the Netherlands Horticulture Council, the Venlo region and the Dutch bank Rabobank).

   Past Floriades have been money-losers, even though they at least leave behind new parks. When this Floriade closes, for example, the Venlo region will have an earth-friendly 164-acre business park with at least two of the buildings easily convertible into office space.

   For better or worse, this Floriade (www.floriade.com) felt very “theme-parkish” to me.

   Curiously enough, attendance is heavier than expected so far with good reviews and visitor surveys giving Floriade 2012 an average rating of 9 out of 10.

   The new approach is certainly more people-friendly. The layout is roomy, the walking paths are wide and well signed, and food and restrooms are plentiful.

   The educational exhibits and pavilions are very well done, and the huge glasshouse called “Villa Flora” had excellent displays of cut flowers, potted tropicals and the latest in houseplants.

This plant-filled living room was one of the most fun displays.

    There’s also plenty of entertainment in the form of international dance, music and acrobatics — another touch that makes theme parks so popular.

   And play areas and hands-on activities are scattered throughout to make this show more kid- and family-friendly than before.

   One of the things our group liked best was the food samples, including Dutch greenhouse-grown strawberries and — believe it or not — radishes dipped in melted chocolate.

   One of my favorite parts was the “Willowman” display, which was a collection of willow-wood nests, tents and bird cages built into trees in a forest nook.

   All in all, there was enough going on to make Floriade 2012 a worthy visit.

   If you’re a “regular” person interested in a day at a plant-oriented theme park, I suspect you’ll like it a lot.

   But if you’re a hard-core gardener looking to be blown away by floral displays, that’s more likely to happen at Keukenhof or Longwood than Floriade.

Accurate size planning heads off this kind of problem.

    Usually it’s a case of people trying to figure out if they have enough space for something. Or they’re trying to avoid house-eating monstrosities.

   But I also get it from frustrated plant-shoppers who have done some homework and found that different growers list different sizes for the exact same plant.

   How can that be? Why can’t everyone agree? And if they can’t, then whom do you believe?

   What it boils down to foremost is how far out you’re using as your guide to estimate size.

   Plants never really stop growing… that is, until the deer eat them or a drought kills them. So you’ll see a different size if one grower or garden center figures on a 5-year size but another uses 10-year (or beyond) sizes.

   I’ve seen a 100-year-old yew bush at Longwood Gardens, for example, that’s easily 25 feet tall and wide. But most people hack yews into 4-by-4 boxes, and most plant tags list them as somewhere close to that range.

   A second complicator is that plants grow at different rates in different settings. I’ve seen the same variety of plant grow to drastically different sizes in different yards.

   Things like soil quality, soil nutrition, soil moisture, light and the temperatures in different microclimates can all make a big difference.

   That explains why one gardener might complain about having to whack back an azalea every year while another gardener says the same azalea in his yard hasn’t gone above 4 feet in 20 years.

   This creates a problem when you’re the one responsible for putting numbers on the plant tags next to “Height” and “Width.”

   The more adventurous types will take a stand and put down, “6 feet tall, 4 feet wide.”

   More conservative types will put down, “4 to 8 feet tall, 4 to 8 feet wide.”

   In the first case, you risk the wrath of gardeners when the plant works its way up to 8 feet tall in, say, 10 years.

   In the second case, you end up with such broad ranges that the numbers don’t help much at all.

One solution: Go by "maintenance size."

    What I usually go by is a good maintenance size. In other words, when a woody plant starts hitting its stride somewhere in the range of 5 to 10 years down the road, what’s a good height and width to keep it at?

   That’s the point where you start pruning it for size-control purposes. Most plants will slow their growth rate as they become more and more mature, but they never grow to a certain size and then just stop.

   It’d be nice if plants had fast-forward and stop buttons, but they don’t (at least not yet).

   Listed sizes are at least usually helpful for determining plant proportions. They’ll tell you if they’re more upright than spreading, for example.

   But don’t take any listed size you see as the gospel truth. Look at tag sizes more as guides or “estimated averages.”

   For what it’s worth, I list good maintenance sizes on all of the hundreds of plants on my “George’s Survivor Plants for Central Pa.” list.

   The list is available as a $5.95 download at http://georgeweigel.net/helpful-info-you-can-buy or you can order a paper copy for $10.95 (includes postage) at the same link.

   Happy planting. This is prime time for getting new trees, shrubs, evergreens and perennials in the ground.

Emerald ash borer adult.

   “I saw this beetle light on one her plants,” says Carey. “I captured it and said, ‘This sure looks like an emerald ash borer.”

   Turns out it was, and with the discovery came the crawling reality that this dreaded, highly destructive tree-killing bug has definitely arrived in the Harrisburg area.

   The discovery is a game-changer for the future of the region’s ash trees – both in home landscapes and especially in the wild.

   We now go from “watchful waiting” to a decision on whether or not to spend money on ash-protecting chemicals.

   First found in Michigan in 2002 as a hitch-hiking invader on wooden packing material from China, the emerald ash borer so far has wiped out an estimated 40 million ash trees in five states.

   It’s been moving relentlessly eastward since, arriving in Pennsylvania’s Butler County in June 2007.

   The state Department of Agriculture tried to quarantine the pest and put out pleas for people to avoid moving ash firewood.

   It didn’t work.

An emerald ash borer trap.

   By last year, traps baited with manuka oil caught Agrilus planipennis in 23 counties. The traps are those purple kite-like contraptions that you may have seen hanging along roadsides.

   “We know how devastating this pest has been in other parts of the country,” says Carey. “It has the capability of effecting the same kind of damage here.”

   The real problem isn’t the adult beetle, which is a hard-shelled bug about the size of an elongated housefly with a shiny, metallic-green back and two big, black eyes.

   The adults do minor leaf damage while they fly around, mate and lay eggs on ash trees from June into early July.

   The “kids” are responsible for the real damage.

   Once the eggs hatch, the skinny, cream-colored larvae bore into ash wood and feed on the tree’s xylem and phloem – the parts that move water and nutrients up and down the tree.

   Within one to three years, even a few borers can kill an otherwise healthy ash tree.

   “This is a very aggressive pest,” says Eric Vorodi, a certified arborist and owner of About Trees Consulting in Boiling Springs.

   If it’s any consolation, at least EABs – as they’re known in the entomology world – go after only species in the Fraxinus, or ash, genus.

   That means if you have a mountain-ash, you’re off the hook since that one is an ash look-alike that’s really a type of Sorbus.

   Which brings us to the matter of what to do if you’ve got ash trees.

   “It boils down to two options, with one of them giving you three more options,” says Vorodi. “One is to wait and see and take your chances. The other is to treat proactively. Once you get (emerald ash borers), though, the chances of controlling them are not good.”

   Like most human ailments, the key is catching an infestation early – or preventing it in the first place.

An ash tree that's already lost most of its canopy and is putting out last-gasp new scrubby growth from the trunks.

   Tree experts say if you wait until an ash has suffered 30 to 50 percent damage, it’s usually too late. Even if you stop further damage, is what you have left worth saving?

   “This isn’t even on people’s radar yet and probably won’t be until we see chainsaws taking down trees,” Vorodi says. “I don’t think most people are going to notice even 30 percent damage.”

   Early signs of damage include a dieback of branches in the tree’s upper canopy along with new scrubby growth emerging from the tree’s trunk. Woodpeckers also may show up in search of a tasty larval meal, and you may notice vertical slits in the bark.

   But the telltale sign is the D-shaped exit hole that a young EAB adult makes as it leaves the tree. The holes are about the size of a pencil eraser.

   Even more elemental, though, is identifying and monitoring any ash trees on your property.

   “If you’re a homeowner and have an ash you’re attached to or consider it to be an important element in the landscape, there’s no reason to lose it,” says Carey.

   If you really don’t want to risk it, Carey suggests soaking the ground around the tree once a year in spring (i.e. now) or fall with imidacloprid.

   Available in garden centers and home stores, one treatment per year controls an estimated 60 to 70 percent of borers, says Vorodi. A commonly available brand is Bayer Advanced Garden Tree and Shrub Insect Control.

   Homeowners also can hire a tree or pest-control company to apply the same chemical or two other choices that only pros can apply.

The tell-tale D-shaped exit hole of an emerald ash borer.

   One is a spray of dinotefuran that’s usually applied to the bark. Like imidacloprid, it controls about 60 to 70 percent of borers for a year.

   The other is emamectin, which gets injected into the trunk and gives nearly 100 percent control for 2 years, according to Vorodi.

   Emamectin injections are more labor-intensive and about twice as expensive per treatment, but since they last twice as long and are considered to be most effective, it’s probably the best long-run option for people who want some ashy peace of mind.

   Bottom line: “How much time and money do you want to spend trying to save your particular tree?” says Carey. “You have to decide which ones you want to hold hands with.”

    Additional sources to help fend off the emerald ash borer:

   * For detailed information and frequently asked questions: www.paemeraldashborer.psu.edu or www.emeraldashborer.info or www.agriculture.state.pa.us and enter “emerald ash borer” in the search box.

   * To identify an emerald ash borer and its damage: http://ento.psu.edu/extension/trees-shrubs/emerald-ash-borer/factsheets/EAB1215.pdf/view.

   * To tell an ash tree apart from similar-looking species: http://ento.psu.edu/extension/trees-shrubs/emerald-ash-borer/factsheets/EAB2942.pdf/view.

   * Options for treating for emerald ash borer: www.emeraldashborer.info/files/Multistate_EAB_Insecticide_Fact_Sheet.pdf

Thanks to the warm weather, weeds are off to a fast start this spring.

   Part of it can be traced to the weather, which was great for germinating winter annuals like creeping veronica (the blue-blooming creeper), chickweed (the white-blooming creeper), purple dead nettle (the lavender-blooming upright with the square stem) and a relative newcomer, hairy bittercress (wiry stems with little flowers emerging from clusters of little leaves).

   These not only got off to an early start but flourished in the warm soil. (For more on this, click here to see my latest weedy Patriot-News column.)

   You might as well get used to this, though, because weed populations are up throughout the United States for a variety of reasons, according to the Weed Science Society of America.

   Here’s a look at what’s been fueling this not-so-welcome trend:

   Extreme Weather

   The erratic floods and droughts that much of the country have been experiencing both can lead to worsening weed problems.

   Flood water is one way weed seeds can move from one location to another, while wet soil is good for both weed-seed germination and subsequent growth.

   On the other hand, drought can kill off planted lawns and gardens, opening the door to bare soil that’s often quickly re-colonized by opportunistic weeds.

   Warmer Weather

   Most noticeable to gardeners is the northward creep of weeds that previously died out in colder winters. Kudzu, for example, has now worked its way as far north as the Canadian shore of Lake Erie. And it even now flowers and sets seed in Pennsylvania, says Penn State weed scientist Dr. Bill Curran.

   Harvard University scientists recently studied the plant life and temperature changes at Massachusetts’ Walden Pond, where Henry David Thoreau meticulously catalogued plants in the 1850s.

   The scientists found that average annual temperatures are now 4.3 degrees warmer, a change that benefited species with the most adaptable germination habits and flowering schedules. Those species are primarily non-native and invasive ones that were not even present in Thoreau’s day, while 27 of the species that Thoreau saw were extinct.

   Rising Carbon Dioxide

   Along with warmer weather has come an increase in carbon dioxide in the air — a trend that research has found benefits weeds even more than ornamentals and crop plants.

   Researchers at the U.S. Department of Agriculture’s Agricultural Research Service found that weeds growing in warmer urban settings with higher levels of carbon dioxide grew, on average, four times taller than the same species in country settings with cooler temperatures and lower levels of carbon dioxide.

Ragweed pollen increases as carbon-dioxide levels increase.

   Worse yet, common ragweed quadruples its pollen output when carbon dioxide levels double, suggesting increasing problems for hay-fever sufferers if the current trend continues.

   An earlier study by USDA found that poison-ivy plants also have been growing bigger and developing more potent rash-causing oil in the last 50 years as carbon-dioxide levels have risen.

   Ride-Hitching Weeds

   A 2011 study by Montana State University researchers found that another underrated way that weeds spread is on the tires, bumpers, wheel wells and undersides of cars and trucks. That’s been an increasing problem as Americans have become more mobile.

   The researchers counted weed seeds on vehicles and found that seeds from roadside weeds are readily picked up, especially in wet weather and in fall. The seeds often travel 160 miles before falling off. In cases where the seeds are caked in mud, they typically stay on until washed off.

   ATVs and other off-road vehicles picked up 20 times as many weed seeds as on-road vehicles. The researchers concluded that frequent washing was the most effective way to control hitchhiking weeds.

   Plant Stow-Aways

   Yet another underrated problem is weed seeds spreading via plants bought in nurseries, stores and garden centers.

Chickweed often hitches a ride to new areas on car bumpers.

   USDA researchers in Alaska bought more than two dozen plants from 29 different nurseries and then incubated the soil in a greenhouse to see what would sprout. They found 54 different species of weeds, especially chickweed, hairy bittercress, groundsel, La Plata sandspurry and Canada thistle.

   They also found more weeds in balled-and-burlapped trees than potted flowers, more weeds in pots with soil-based mixes than soilless potting mixes, and a big difference between growers using good weed control and weed prevention vs. those not controlling weeds.

   Bird Feeding

   An unwanted side effect of the trend toward attracting birds to the backyard garden is more weeds — both on the feathers of the birds and in the seed that gardeners are buying for them.

   Oregon State University researchers examined the weed seeds in 10 brands of retail wild bird seed and found that all brands had at least one species of weed. Half of them had six or more species.

   The samples generated 50 different kinds of weeds, including 10 of Oregon’s most noxious invasives.

   The researchers’ suggestions for bird-feeding weed control: use feeder trays to keep seeds from falling on the ground; buy baked or treated brands; be vigilant to prevent weeds and eliminate them early before they set seed, or stick with non-weedy food sources such as sunflower hearts, peanuts, peanut butter, raisins, mealworms and suet cakes.

   Herbicide Resistance

   One last concern with controlling weeds is species that are increasingly able to survive weed-killers. A function of evolution, the surviving weeds are passing along their herbicide resistance to offspring.

   The Weed Science Society of America reports that ragweed, horseweed, johnsongrass and hairy fleabane are among the weed species becoming increasingly resistant to the widely used herbicide glyphosate (i.e. Roundup).

   So as another weedy season unfolds, keep your diggers handy and your back in good shape.

   It doesn’t look like we’re heading for any weed-easy seasons any time soon.

Hairy bittercress is a weed that's off a terrific start this year.

   The same extraordinarily warm start that had our dogwoods blooming three weeks early has been a boon to weeds as well — especially ones that sprout from seed in late winter to early spring.

   So-called “winter annual weeds” such as purple deadnettle, chickweed, creeping veronica and a relative rookie invader known as hairy bittersweet have been rampant in lawns and garden beds everywhere.

   “We’ve got two things going on,” explains Dr. William Curran, a weed specialist with Penn State Extension in State College. “One is the mild weather. Everything came alive two or more weeks earlier this year.

   “Why weeds are more prevalent is harder to answer. It could be the series of warm winters has caused a slow buildup, and now we’re exploding with weeds. Or it could be that winters are not killing off things that normally would die in the cold.”

   Curran says he’s seen a gradual northward creep of weeds that we didn’t even used to have.

   A classic example: kudzu, the “vine that ate the South.”

   “We’ve had kudzu in Pennsylvania for years, but we never thought of it as something that would flower and set seed in Pennsylvania,” says Curran. “It does now.”

   Weeds that spread by seed spread much farther much faster than weeds that spread mainly by creeping.

Mare's tail.

   Mare’s tail (a.k.a. “horseweed”) is another weed that’s new trouble here. This tall pest with the skinny leaves and wispy yellow flowers once was mainly a Philadelphia-area problem but has expanded its range.

   And our worst relative newcomer has been hairy bittercress, a ground-hugger that starts out as a patch of tiny rounded leaves but soon sends up foot-tall wiry shoots with tiny white flowers at the tip.

   But even our old not-so-favorites are having a banner season so far.

   Creeping speedwell and chickweed got off to an early start and flourished because of the lack of snowcover to block sunlight, plus warm soil to fuel its roots.

   Speedwell is the low creeper that blooms blue, while chickweed has similar clusters of small leaves but blooms white.

   Henbit and purple deadnettle are two others off to a great start, both in low-attention lawns and unmulched garden beds.

   Often confused because they look so similar, both are winter annuals that send up mint-like square stems and produce light lavender flowers.

Purple dead nettle.

   Home gardeners aren’t so much concerned with what’s what as how to keep weeds from overtaking the landscape.

   For weeds that are already up, “you’re looking at removing them by hand or by hoe, or by using some type of foliage herbicide,” says Curran.

   Annual weeds usually come up easily since they’ve only had a few weeks to grow since emerging from seed.

   Perennial weeds are tougher because they’re returning from roots. These usually require some sort of mechanical loosening (weeding knife, screwdriver, etc.) to lift out all of the roots.

   A kill-most-everything-green product such as glyphosate (the ingredient in Roundup) is an option in garden beds, while a broad-leaf weed-killer is an option in lawns.

   Just don’t let glyphosate spray drift onto the leaves of plants you don’t want to kill.

   In the lawn, Curran says spot-sprays of liquid broad-leaf weed-killer (Ortho’s Weed B Gon is the best-known example) are more effective than granular “weed and feed” spread over the whole lawn.

   After dispatching what’s already up, kick into prevention mode.

   Crabgrass, for example, is just starting to germinate.

   It’s not too late to put crabgrass-preventing products on the lawn. Do it soon, though, if you’ve had a problem with this grassy weed in the past and want to keep it from getting out of control by summer.

   Ditto with landscape-bed weed-preventers, such as Preen or corn gluten meal. While these granular weed preventers won’t stop already-germinated winter annuals or perennial weeds returning from roots, they can stop weeds yet to germinate from seeds.

   That includes the champion of mid-spring weeds, the dandelion, as well as summer weeds, such as pigweed, purslane, ragweed and lamb’s quarter.

   Then there’s mulch. Now’s a good time to cover any bare soil with a total of 2 to 3 inches of organic mulch (bark chips, leaves, shredded wood, etc.) to smother weed seeds in the soil.

   Keeping that “seed bank” under control is critical to long-term victory over weeds, says Dr. Robert Norris, a retired professor of plant sciences at the University of California at Davis.

   Norris once did research that found that a single chickweed plant could produce 25,000 seeds, while purslane could produce a staggering 2 million seeds per plant.

   His suggestion: mulch to keep new weeds from coming up and hoe or pull every weed before it flowers and seeds.

   “Diligence is the key,” he says. “Never let one weed go to seed or you will be back to square one.”

   Keep pulling and keep new seeds out (most drop near the parent plant instead of blowing in), Norris says, and you’ll bankrupt the weed-seed bank in an average of 5 years.

   You might never end up totally weed-free, but a drastic reduction still would be nice.

   Especially right now.

Dividing perennials not only contains the spread of growing perennials, but it gives you free plants.

It works best for perennial flowers — the ones that come back year after year (that is, when deer, rabbits and groundhogs don’t eat them).

Basically, you:  a.) Dig up the whole clump, b.) Separate the clump into two or more fist-sized pieces, and c.) Replant the divisions as you would a new plant.

Ta-daaa! You’ve now got free new plants that are exact copies of what you started with. Trade with neighbors to diversify both of your yards.

Doesn’t this risk killing the plants?

It sounds ruthless, but so long as you separate big-enough pieces (i.e. fist-sized or more) and keep the planted pieces watered afterward, the survival odds are very high.

Division actually reinvigorates many older perennials and reduces disease. Younger sections replanted from the spreading perimeter usually bloom nicely the next season.

When’s the time to divide?

Early spring and early fall are two excellent times for most species. That’ll give the roots several weeks to establish at a lower-stress time than in the heat of summer.

In general, divide perennials when they’re not blooming. Fall bloomers such as mum, aster, sedum, goldenrod and Japanese anemone are best divided in spring. Spring bloomers such as creeping phlox, foamflowers, salvia, sweet woodruff and dianthus are best divided in early fall.

Most summer bloomers can go either way.

How do I get the pieces apart?

Some plants simply pull apart. You’ll be able to grab a section of stems and pull them — roots and all — apart from the mother.

Examples are blackeyed susans, coneflowers, hardy geraniums, lamium, Shasta daisies, salvia, foamflowers and, most of the time, daylilies, liriope and asters.

Other plants have roots that are tightly interwoven, so you’ll have to use a shovel, knife or even an ax to split these clumps.

Examples: ornamental grasses, iris, astilbe, hosta, sedum, yarrow, goats beard, mums, coreopsis, dianthus, ferns and catmint.

Any I shouldn’t try to divide?

Baptisia is an example of a deep, tap-rooted perennial that doesn't divide very well.

Perennials with deep, single tap roots and ones that have habits similar to woody shrubs don’t divide. These include baptisia, Russian sage, butterfly weed, baby’s breath, artemisia, lavender, columbine and euphorbia.

Anything else I need to do?

Work compost into the soil before replanting. That’ll improve drainage and add fresh organic matter and nutrition.

Replant divisions at the same depth as the mother plant.

Scratch a little balanced, granular fertilizer into the soil at planting, and water twice a week until the ground freezes whenever rain doesn’t do the deed for you.

Two good books on dividing and caring for perennial flowers:

“The Well-Tended Perennial Garden” by Tracy DiSabato-Aust (Timber Press, 2006, $34.95 hardcover)

“The Perennial Care Manual” by Nancy J. Ondra (Storey Publishing, 2009, $24.95 paperback)

New growth of foamflower 'Sugar and Spice' piggybacking on top of last year's dark foliage.

   Each day a different plant comes back to life or pushes out flower buds or takes one step more toward peak beauty.

   I’d have to rank it as my favorite time of year.

   I thought I’d share some pictures and observations of what caught my eye this week. No advice, no studies, no hard-core plant info… just some neat goings-on.

   One of my favorite shade plants is foamflower ‘Sugar and Spice,’ and this little bicolor beauty started putting out flower stems and fresh green and burgundy leaves this week above last year’s darker leaves.

   Winter didn’t do much damage at all to the old foliage, so I didn’t cut it. The color just turned a rich burgundy.

   The new leaves are emerging from this rosette of burgundy, almost like a fountain. The effect is that it seems like a new plant is piggy-backing on the shoulders of another.

   I’ll eventually cut the older leaves as they fade into the sunset, but for now, this is one interesting foamflower.

Creeping sedum 'Angelina' and dark-leafed coralbells.

   I’ve got a patch of golden creeping sedum ‘Angelina’ edging a group of dark-leafed coralbells, and both of these also came through winter fine. They’re already making a bright and solid contrast under a ‘Beni Otake’ Japanese maple tree at my back left house corner.

   Not everyone likes lamium, but I think there are some beautiful varieties of this creeping perennial, especially the pink-flowering, white-variegated ‘Pink Chablis’ and the white-flowering, white-variegated ‘White Nancy.’

   My patch of ‘Pink Chablis’ colored up nicely and is already blooming pink on a shady side of my back patio (protected by a dogwood and three ‘Double Pink Knock Out’ roses).

   Don’t confuse lamium with the overly aggressive, yellow-flowering lamiastrum, also known as yellow archangel. That one is fine all by itself on a shady, rocky bank. But it makes a terrible neighbor in a garden.

   And another of my favorites is barrenwort (Epimedium). I’ve got a patch of barrenwort ‘Rubrum’ under a dogwood that’s now in full bloom with dainty, pink flowers hanging below the newly emerged yellow-green heart-shaped leaves of this under-used shade plant.

   We’re still running about 3 weeks ahead of schedule, from what I can tell by what’s blooming when.

Barrenwort 'Rubrum' in flower.

   Like a lot of people, I’ve already got lilacs starting to flower. My blueberries have been in full bloom for more than a week.

   Early-March-planted lettuce is ready to start clipping.

   A lot of my tulips already have come and gone.

   My ‘Prairifire’ crabapple tree out front is opening its rosy-magenta flower buds – way earlier than I’ve ever seen it bloom.

   And buds are already starting to pop out from some of the latest spring waker-uppers, such as American fringetree and crape myrtles.

   I’ve heard reports from record-keepers at public gardens saying some plants are beating their earliest-ever bloom times by a full 2 weeks.

   Who knows what kind of weather we’ll get from here on out, but for now, I’m enjoying the hand we’ve been dealt.