Lessons from the 2021 Gardening Season

November 9th, 2021

   Buggy and wet.

Soggy spells this summer led to some of this…

   That sort of sums up the 2021 gardening season, although there were enough nice days and sunshine rays to rate it at least a “decent” on the scale of growing fitness.

   Here’s a look at six key take-aways and lessons to be learned from the 2021 season:

Get used to the “new normal”

   This year was a model of what climate scientists say we ought to get used to as our climate continues to change – earlier springs, hotter summers, increasingly erratic changes in temperature, and more weather extremes that alternate between ever-heavier rain dumpings and “flash droughts.”

   January, March, and April all were at least three degrees warmer than usual, and by April 23, we were done with frost in Harrisburg.

   That continued our trend of generally earlier last spring frost dates, although never count out the possibility of a one-off frozen night even into mid-May (as happened May 10, 2020).

   According to the most recent frost data from the National Weather Service, the median last freeze date now for Adams, Cumberland, Dauphin, Franklin, Lancaster, Lebanon, and York counties is April 11. That means that in half the years, nighttime freezes are done by that date in those counties. (Note that median is different from average last spring frost dates and is very different from the all-time latest freeze, which remains May 12 for Harrisburg and is what cautious gardeners go by when planting their summer vegetables and annual flowers).

   The median date for fall’s first freeze is now Oct. 21 for most of south-central Pennsylvania but Nov. 1 for Adams, Lancaster, and York counties, according to NWS data.

   March, April, May, and June gave us a drier-than-usual start to the growing season (all had less-than-normal rainfall), but then someone turned on the faucet.

   Harrisburg got a three-inch dumping July 11 and 12, nearly six inches of rain in August (two more than normal), then the Ida dumping plus three more inch-plus rains to put the area nearly a foot of rain above what we usually get in July, August, and September.

   It was hot, too. June, July, August, and September all registered above-normal monthly average temperatures.

   Including May, Harrisburg ended up with 34 days of 90-degree or higher temperatures this growing season.

   The upshot of all of this for gardeners is that we’re now able to grow plants we couldn’t just a decade or two ago (crape myrtles, osmanthus, laurels, figs, etc.) while plants on the fringe of their northern range here are beginning to suffer (Colorado blue spruce, sugar maple, heather, American beech, etc.)

   We also should consider using more plants that can take our increasingly hotter summers.

Read George’s 2020 post on gardening in our changing local climate

See George’s list on 10 trees that can take our future heat

See George’s list on 12 annual flowers that can take high heatRotting roots

   All of that rain in July, August, and September caused a few plant problems, the most serious of which was rotting roots of trees, shrubs, and evergreens that were planted in poorly drained soil.

   Some plants can tolerate only a few days of saturated soil before they begin a slog toward death, as many gardeners have seen first-hand.

   Unfortunately, there’s not much you can do once that happens.

   The solution is to pay attention at planting time and either limit your planting to well drained sites or improve drainage by working compost into the soil and creating raised beds before planting.

   For plants struggling but still alive in sites that you now realize are poorly drained, one option is to dig them and either move them to drier ground or dig in compost and replant in that improved spot.

   You could also redirect runoff that might be causing soggy spots by extending roof drains, digging swales, and building retaining walls.

Moisture-fueled diseases

   This summer’s rainy and humid conditions also were ideal for fueling a variety of plant diseases.

2021 brought us lots of leaf diseases. Tomatoes like these were particularly hammered.

   Gardeners saw plenty of leaf diseases that spotted, blackened, and/or blighted our flowers and tomatoes but also lots of more serious root-rotting pathogens that threatened trees, shrubs, and evergreens.

   Cleaning up and removing fallen diseased leaves is a good non-chemical, end-of-season way to counteract leaf diseases. Every diseased leaf that you rake up this fall is one less with fungal spores that could overwinter and reinfect your plants next year.

   The good news is that leaf diseases are mainly cosmetic. They seldom kill plants and may not even happen next year if conditions are dry instead of wet or humid. So don’t panic if your woody plants dropped disfigured leaves early; odds are they’ll leaf out fine again next spring.

   Root-rot diseases such as phytophthora and pythium, on the other hand, are much more serious threats than leaf diseases and are not easy to diagnose or control either.

   These diseases often flourish underground before the plant shows symptoms above-ground. And they may not even kill until the following season when the compromised roots are unable to support plants once they kick into high growth gear next spring. That’s when the plant seems to “mysteriously” die.

   The lesson: Plant deaths that happen next spring and summer could be related to the wet weather we had this season.

Invasion of the armyworms

   One of the most novel and alarming bug issues we had this year was in late summer when a lot of lawn-owners started seeing large patches of their turfgrass brown out – seemingly overnight.

Armyworms are caterpillars that chewed our lawns big-time this summer.
Credit: Nick Sloff, Penn State University

   This turned out to be the work of a grass-munching southern caterpillar called the armyworm that blew here on the strength of tropical-storm winds. Researchers believe they came the whole way from southern Texas.

   We occasionally see some damage from armyworms, but this year’s outbreak was the worst since the 1990s and was very destructive to hayfields in addition to home lawns.

   Two bits of good news.

   One is that armyworms don’t survive our winters and die when temperatures go below freezing.

   That doesn’t mean we won’t be seeing them again… just that if we do, new ones will have to blow in again from warmer climates.

   The second plus is that these caterpillars feed on the blades of grass but generally spare the crowns (the point from which the blades arise) and the roots (unlike damage done by beetle grubs).

   The result is that lawns may grow back on their own – by next spring if not already.

   If your lawn was attacked by armyworms and you’re not seeing recovery once grass starts growing next April again, you’ll have to reseed – or use the dieback as an opportunity to plant a new garden or meadow.

Cicada “flagging”

   The other rare bug appearance came from the Brood X cicadas – curious locust-like insects that emerge from the ground only once every 17 years.

This is what cicada “flagging” looks like on an oak tree.

   Billions of these woke from their slumber by mid-June and made quite a noisy racket while “singing” their mating call. Females then laid their eggs in tree branches, and all of the adults were dead and gone by July.

   The cicadas did little serious, lasting damage to plants. The main threat was to young tree saplings, which are more at risk from the slits that females make in branches to lay their eggs.

   You might have noticed brown leaves toward the end of a lot of tree branches – big and small – this summer, which is a condition known as “flagging.” What happens is that the branch tips die outward from the point where the cicadas make their slits.

   Most trees will grow through this tip damage and push out new growth next spring, looking no worse for the wear in most cases.

   Otherwise, you might need to do a little cosmetic pruning to reshape your damaged tree toward the end of winter.

   We see annual cicadas and other, smaller periodic broods every year, but the big, 17-year Brood X won’t be back until 2038.

Those bugs with the spots

   Many gardeners got their first look this year at the spotted lanternfly, that inch-long grayish-brown bug with the spotted backs and orange set of under-wings (seen only when its wings are fully open).

Lanternfly nymphs are shown in the two photos at left, while an adult with open wings is pictured at right.
Credit: Penn State Extension

   Like the cicadas, this is another bug that you either saw in great numbers or didn’t see at all.

   The lanternfly is now in 34 Pennsylvania counties and nine eastern states after first arriving from Asia in southeastern Pennsylvania in 2014.

   It’s not in every nook and valley of south-central Pennsylvania (yet), but some gardeners were alarmed when they saw hundreds of adult lanternflies congregating in late summer into early fall on favorite plants, such as grapes, black walnut, river birch, willow, sumac, red maple, silver maple, and the weedy tree of heaven.

   Actually, many gardeners were puzzled earlier in the summer when they saw the nymph forms of the lanternfly for the first time.

   The nymphs don’t look anything like the adult. After hatching from overwintered eggs in spring, the first three stages of lanternflies are little beetle-like crawling bugs with long snouts. They’re black with white spots. Then they morph into long-snouted little beetle-like bugs that are orange with black lines and white spots.

See Penn State Extension images of different stages of lanternflies

   The good news is that lanternflies aren’t a terribly destructive bug – unless you’re in the fruit-growing or wine-making business. Grapes are one plant that lanternflies kill.

   They also feed on and can harm hops, young nursery plants, and several tree species, especially young black walnuts and trees of heaven. But in the landscape, entomologists consider lanternflies to be more of a nuisance that can stress landscape plants but not kill them.

   Especially in newly infested areas, lanternfly populations can fluctuate widely from location to location and from year to year.

   Penn State Extension says that factors such as weather, natural enemies, and plant makeup can lead to a lot of variability. In other words, it’s not unusual for a heavily infested area to have a light infestation the next year, and alternatively, for a lightly infested area to explode with lanternflies the following year.

   Freezing temperatures will kill adult lanternflies, but the eggs they laid in September and October will hatch into new lanternfly nymphs next spring.

   One of the best ways to control outbreaks is to scout now through winter for lanternfly egg masses.

   The masses look like smears of grayish-brown putty and can be found on tree trunks as well as non-plant surfaces such as rocks, awnings, fences, outdoor furniture, even car tires.

   If you smash these masses with something hard and flat like a tongue depressor, putty knife, or even an old credit card, you’ll prevent 30 to 50 future lanternflies in a few seconds… without chemicals, too.

See a Penn State Extension video on destroying egg masses

   By the way, lanternflies don’t sting, they don’t bite, they don’t try to get inside your house in winter like stinkbugs, and contrary to their name, they don’t glow either.