Winning the Weed War

June 2nd, 2015

Late spring is when the landscape looks better than just about any other time because plants are in peak growth mode and generally blooming their heads off.

The best way to stop this from happening is to prevent weeds in the first place… or get rid of them when they’re young.

Unfortunately, weeds are plants, too. And they also kick into peak production in late spring.

Spring rains and warmth wake up gazillions of slumbering weed seeds deposited by prior year’s weed flowers, wind, birds and other weedy origins. (See more details on that in a post I did called “Weedfest.”)

Being ready for that is the key to winning the weed war. In other words, we have to get them before they get us.

Look around the yard, think like a weed, and figure out where you’d put down roots. If you’re like most weeds, you’ll head for bare dirt. Any little bit will do.

If you’re a plant geek like me, you’ll opt to beat weeds to the punch by putting plants in every last bare spot before weeds get there.

That means overseeding the lawn with grass seed to thicken it up; spacing garden plants so they touch when mature; tucking low-growing perennial or annual flowers under and around trees and shrubs, and filling in bigger bare spots with a groundcover planting.

This is also where mulch becomes your best ally.

Two to 3 inches of an organic mulch is plenty to snuff out most weeds while retaining moisture and feeding the soil at the same time. Just don’t overdo it.

I like pine bark mulch best for most settings. This is bark from evergreens that’s ground to a texture fine enough that it won’t blow away and porous enough that it doesn’t mat like shredded hardwood (ground-up wood and bark).

Most importantly, bark mulch is less likely to grow the dreaded artillery fungus that shoots those little tarry black dots on your house siding and new white car.

Fungus-friendly shredded hardwood (a.k.a. “tanbark”) is fine away from houses and white fences and is a good choice on banks, where the shredded pieces knit together and resist washing downhill in a storm.

Cedar or cypress mulch also is fungi-resistant (if you don’t mind paying more for it), and composted leaves from the municipal pile work fairly well, too (if you don’t mind hauling them and adding them more often since they break down quickly).

If you have plenty of mulch from prior years, just top if off. Don’t add 3 inches every year if some is intact from previous years.

I’m not a big fan of weed fabric or black plastic under mulch. Grassy weeds like nutsedge manage to poke up through the fabric’s tiny holes, and all sorts of other weeds germinate on top of fabrics and plastic as the mulch topping breaks down.

I’ve found that fabrics and plastic also interfere with the soil’s ability to “breathe.” And they hinder rainfall in a drought and encourage rotting in monsoon years.

Weeds are germinating on the top of this bed that’s protected with a weed fabric topped with a light layer of stone.

When you go to plant, don’t till or dig anymore than you have to. Every time you turn over soil, you’re stirring up weed seeds that will germinate in their new warmer, brighter location closer to the surface.

In the lousy compacted clay and shale that most of us start out with, you have no choice but to turn that and improve it. But once you’ve initially improved a bed, just top it with compost and/or mulch instead of tilling every year.

Be careful what you add to the soil, too.

Rotted horse manure is great for the soil, but you’re likely to import weed seeds if you’re hauling manure that’s been piled up in a field for a year or two.

Composted municipal leaves, bagged soil amendments and your own homemade compost are least likely to contribute to weed problems, especially if you regularly turned your pile and avoided adding weeds that had gone to seed.

As weeds emerge, take a look to see what kind you have.

You don’t necessarily have to know the name of every weed, but it helps to at least figure out if it’s a perennial weed (one that grows back each year from last year’s roots) or an annual weed (one that sprouts anew from a weed seed).

The difference will determine your plan of attack.

Various weed-preventing products are available in garden centers to stop new weeds from sprouting from seed – provided you get the products down right before the seeds germinate.

In spring, the time frame begins for most weeds around the time forsythia is hitting peak bloom. However, some “winter annual” weeds actually germinate in late winter, while warm-weather weed species germinate in later spring into summer.

Preen and Jonathan Green Weed Screen are two commonly found chemical granular brands. Concern Weed Prevention Plus, Preen Vegetable Garden Weed Preventer and Cockadoodle Doo Organic Corn Gluten Meal are three non-chemical weed-preventers for organic gardeners. Numerous crabgrass preventers are available to head off crabgrass outbreaks in the lawn.

Keep in mind these are all weed preventers, not weed killers. They won’t do anything to kill already-sprouted weeds, and they won’t stop perennial weeds from regrowing.

Weed preventers also don’t stop all types of annual weeds from germinating. (The labels tell you which ones.) So what can happen is you can still end up with a lot of weeds… they just might be all of one or two types instead of 10 different kinds.

Weed preventers usually help at least somewhat, and one of their advantages is that you can spread them over shrub and perennial beds without harming the “good” plants (read the labels for exceptions).

However, weed preventers also usually start to run out of steam after about 10 or 12 weeks, so for season-long control, consider a second application in June.

For weeds that are up and growing, the quickest, cleanest approach is to simply yank the dratted things, roots and all. Use a weeding tool or a screwdriver to loosen the soil so you aren’t just ripping the heads off the weeds.

Weeds are a lot easier to pull when they’re babies than when they get to this size…

The sooner you get to it, the better. Baby weeds are easier to pull, but more importantly, you’re getting them before they go to seed and set the stage for even worse problems later. (Weed plants typically produce hundreds if not thousands of weed seeds each.)

If you’re not keen on hand-pulling, garden centers will gladly sell you all sorts of chemical weed-killers.

Read the label to be sure you’re getting the right kind.

There are weed-killers that kill broad-leaf weeds but not grassy ones (usually for use in lawns), there are some that kill grassy weeds but not broad-leaf ones (useful when goosegrass invades the bank of junipers or vinca), and there are some that kill just about anything that’s green.

For kill-all sprays like Roundup and full-strength vinegar from the kitchen, be careful that the spray doesn’t drift onto neighboring plants that you don’t want to harm. Use a sprayer shield or at least a piece of cardboard to contain the spray.

Once you’ve cleaned up the early mess and either prevent the rest or pluck them young, go on regular weed patrols the rest of the year.

Remember, not all seeds germinate in the spring. Plus, new seeds are always blowing in from that empty field down the road or being carried in on the feathers of those birds you’ve been working to attract.

On the bright side, about three-quarters of a season’s weeds are usually up and growing by the end of June.

For help identifying weeds, two good online sites with photos are Rutgers Cooperative Extension at www.rce.rutgers.edu/weeds and Virginia Tech University at http://oak.ppws.vt.edu/~flessner/weedguide.

An excellent book with photos and growth habits of most weeds is “Weeds of the Northeast” by Richard H. Uva, Joseph C. Neal and Joseph M. DiTomaso (Comstock Publishing Associates/Cornell University Press, 1997, $29.95 paperback).

An excellent book on weed control is “Weedless Gardening” by Lee Reich (Workman Publishing, 2001, $8.95 paperback).

Common weeds found in central-Pennsylvania gardens, listed by whether they’re grassy or broad-leaf types and whether they’re annual or perennial ones:

* Grassy Annuals: annual bluegrass, barnyardgrass, crabgrass, goosegrass, shattercane, wild millet (broomcorn millet), witchgrass, yellow foxtail.

Nutgrass (nutsedge) has an extensive root system. New shoots can come from bulblets or pieces of roots left behind, which makes it hard to eradicate by pulling.

* Grassy Perennials: bermudagrass, dallisgrass, johnsongrass, nimblewill, nutsedge (nutgrass), orchardgrass, quackgrass, reed canarygrass, tall fescue, timothy grass, velvetgrass, wild garlic (wild onions), wirestem muhly.

* Broad-leafed Annuals: annual sowthistle, black medic, burcucumber, cocklebur, common chickweed, common mallow, corn cockle, devils beggarticks, dodder, eastern black nightshade (deadly nightshade), field pepperweed (field cress, peppercress), field violets, groundsel, hairy bittercress, hairy galinsoga, hairy vetch, hedge mustard, henbit, horseweed, jimsonweed, knawel, lamb’s quarters, mile-a-minute weed, Pennsylvania smartweed, pigweed, pineapple weed, prostrate knotweed, prickly lettuce, purple cudweed, purslane, ragweed, redstem filagree (sometimes biennial), scarlet pimpernel, shepherd’s purse, spotted spurge, velvetleaf, white campion, wild mustard, wild radish, yellow rocket (sometimes biennial).

* Broad-leafed Perennials: bindweed, bittersweet nightshade, bull thistle (biennial), burdock (biennial), Canada thistle, chicory, cinquefoil (potentilla), creeping speedwell (creeping veronica), curly dock, crownvetch, dandelion, dogfennel, goldenrod, ground ivy, hawkweed, horsenettle, Japanese honeysuckle, Japanese knotweed, kudzu, milkweed, mouse-ear chickweed, moneywort, mugwort (chrysanthemum weed), mullein (biennial), multiflora rose, oriental bittersweet, oxeye daisy, perennial sowthistle, plantain, poison hemlock (biennial), poison ivy, pokeweed, purple loosestrife, red sorrel (sheep sorrel), smooth groundcherry, spotted knapweed, stinging nettle, teasel (biennial), tree-of-Heaven, western salsify (biennial), white and red clovers, wild blue violets, wild carrot (biennial), wild strawberry, woodsorrel, yellow toadflax.