What to keep alive and what to let go
The thing about summer rain is that some areas get enough soakings to keep plants growing while others – sometimes very nearby – miss every last downpour.
Whether spotty or widespread, extended dry spells require the gardener to pick up the slack.
But unsustainable water bills, the prospect of running a well dry, or just lack of time to keep up with unrelenting hose demands can lead to the need for triage at some point.
Triage is the tough decision on which plants really need water to stay alive and which can be sacrificed to nature’s whims. The current brutal heat only adds to the dilemma.
If you can’t water everything, it makes sense to focus limited water and time on the plants that are most valuable to you.
Maybe it’s the priciest plants like that $200 new tree or the bed full of shrubs and perennials that the landscapers just installed in May. But it also could be something of sentimental value, such as a peony division handed down from Grandma or a rare heirloom tomato variety.
Either way, the question to ask is, “Which plant losses would hurt most if I don’t water?”
Keep in mind that any new plant is more at risk of drought injury/death than existing, established ones.
Even drought-tough species aren’t very drought-tough until their roots occupy enough ground space to mine what moisture they need to survive.
Most perennials and ornamental grasses are in reasonably good root shape after two years in the ground, but trees, shrubs, and evergreens can take three to four years to adequately root-establish.
The upshot is that a five-year-old dogwood might be able to go weeks without water while the exact same variety in the same spot might need a good soaking twice a week if it was just planted this spring or last fall.
Ditto for lawns.
Turfgrass that’s two or more years old generally can go a month without water even in its dormant, summer-brown stage, while new grass (less than a year old) will die much sooner due to its limited root system.
That means an established lawn can go to the bottom of the triage list, especially since lawn irrigation requires a lot of water. However, replacing a whole lawn is expensive and labor-intensive, so a new one might rate high placement.
Another low-on-the-list possibility involves annual flowers, container plantings, and vegetables.
Most of these are going to die come frost at the end of the season anyway.
If you can live with the possibility that your petunias and zinnias might croak in August instead of late October, then those are candidates to go off hose-fed life support.
Container plants need water every day or two in hot weather, so unless you really like (or need) them to the bitter end, then they’re also sacrificial candidates. At least you got three months out of them.
And although it’s not easy to walk away from wilting beets or tomatoes in their prime, at least you can divert would-be water expenses into grocery-store-bought substitutes.
Most plants are pretty good about letting you know when they’re starting to run into water trouble.
Wilting that doesn’t fix itself in the cooler, darker conditions overnight is one of the first signs (although it’s more accurately a sign that the best time to water was yesterday).
A second dry-soil indicator is when plants begin to lose their vibrant color. Evergreen needles may turn a duller green, for example, while flower leaves might start to yellow.
Leaves that curl upward are another sign that plants are trying to conserve moisture. Curled leaves are a plant’s way of trying to limit evaporation loss by exposing less surface area to wind and light.
Although it’s a little more subtle, slowed or no growth is another ploy in a plant’s bag of survival tricks. Look for leaves that are no longer expanding or the lack of new and/or extending shoot tips.
Less subtle and more serious, though, is when existing foliage starts to brown around the tips and margins. That’s a sign that damage is already taking place.
The next stage of trouble is when plants begin dropping foliage altogether as a way of getting rid of their main moisture-losing parts.
For perennials and leaf-dropping (deciduous) woody plants, that’s not a good thing but maybe not fatal – if you get them water ASAP. However, for needled evergreens, by the time needles are brown and dropping, the plant is already dead.
The last-gasp stage is when roots and whole branches start to die. Beyond that fork in the road, the next destination is a kaput plant. At that point, you can deliver all the water you want, and it won’t matter.
If it helps any in the meantime, try dividing the yard into zones. Instead of watering the whole yard full of plants every few days, break up the job by watering one zone one day then another zone another day – focusing just on the plants most at need.
Use your finger or a water meter to gauge if and when an area needs water. Remember, the goal is to keep the soil consistently damp all around and to just below the roots. Checking that first-hand (or first-finger, as the case may be) is much more accurate than watering by the calendar.
- Read George’s eight summer plant-watering hacks
- Read George’s post on why it’s so important to get watering right
- Read George’s column on how to keep plants alive in the heat of summer
- Read George’s column on how to keep plants alive during summer vacations
Adult spotted lanternflies have a distinctive spotted red-orange set of wings.
The grownups are here
Our newest bug pest, the spotted lanternfly, continues to make its way through Pennsylvania, and many gardeners and yardeners are seeing masses of them for the first time this year.
Lots of midstaters have been puzzled since late spring at unfamiliar little spotted bugs that hop when disturbed. At first, they were black with white spots and more recently red with white spots and black trim.
Both were nymph stages of the spotted lanternfly. Now this bug is morphing into its very different-looking adult stage – a gray flying bug, about the size of a pinky tip, with black spots on the wings.
When the adults go to fly, they open a second set of wings that reveal a distinctive red-orange color with black spots.
Given that a lot of residents were reporting sudden hordes of the nymphs earlier this summer, the likely scenario is hordes of adults in the coming weeks.
The adults fly around, mate, and lay eggs before dying off for the season in November. The overwintered eggs then hatch next spring to start a whole new cycle.
The curious thing is that spotted lanternflies seem to be a, well, spotty problem. People who had masses of them last year might have few to none this year, while those who never had any before are suddenly inundated.
And lanternflies can show up in epic proportions in one neighborhood but number few and far between in another.
Penn State entomologists believe that the fluctuations are influenced by the availability of favorite plants, natural enemies, and even weather.
Adult lanternflies are fond of grapes, river birch, willow, sumac, silver and red maples, and especially the invasive tree-of-heaven. Home gardeners have reported nymphs on cucumber, basil, rose, peony, and Russian sage – up to a total of at least 70 species altogether.
While hordes of lanternflies and their resulting “honeydew” (liquid waste) are an undoubted nuisance, this bug isn’t a widespread plant-killer.
The biggest exception is the damage they do on grapes. However, lanternflies do have the potential to cause damage on landscape plants that already are stressed by other problems... and when heavy feeding occurs several years in a row.
For those reasons, Penn State Extension advises treatment decisions on a case-by-case basis.
One option is doing nothing since the bugs don’t sting, bite, or transmit disease and probably aren’t going to decimate a landscape.
A second option is trapping lanternflies as they move up and down trees to feed. “Circle traps” and sticky bands with wildlife barriers are two DIY choices.
A third option – if you have the time, patience, and “ick-factor” tolerance – is squishing lanternflies one by one.
And a fourth option is insecticides.
According to Penn State Extension, effective sprays include organics such as insecticidal soap, neem oil, horticultural oil, and natural pyrethrins as well as the synthetic insecticides bifenthrin, beta-cyfluthrin, carbaryl, malathion, and zeta-cypermethrin.
For killing lanternflies higher up in trees, Penn State lists two systemic chemicals – a soil drench that homeowners can buy containing imidacloprid and the chemical dinotefuran that professionals can apply via trunk spray, soil drench, or trunk injection.
Come fall through winter, scraping/squashing egg masses is a fifth control option.
Penn State Extension has an excellent Spotted Lanternfly Management Guide that includes photos, details on controls, and a rundown to help residents decide whether to treat or not.
This is the foliage of a honeylocust tree, which is a favorite feeding ground of the mimosa webworm.
Honeylocust trees turning brown?
If your honeylocust trees are turning brown, it may not be hot, dry weather – especially if you notice small silky webs around clusters of leaves. The damage probably is the work of a bug called the mimosa webworm.
This insect technically isn’t a worm but a caterpillar that feeds on its namesake tree… and even more so, on thornless honeylocusts, especially the popular variety ‘Sunburst.’
Thornless honeylocust became a common landscape tree because a.) it’s not easy to kill, and b.) it has small leaves that make it less “messy” in the eyes of those who don’t like to rake leaves.
We have two and sometimes three generations of these caterpillars per year in Pennsylvania. The first generation of caterpillars begins feeding in mid to late June most years, but it’s usually not until August that tree-owners notice damage as the leaves turn brown and the second generation is at work.
Although mimosa webworms damage mimosa and honeylocust trees cosmetically, they seldom severely stunt or kill them.
The browning occurs late enough in the season that trees grow through the setback, although they sacrifice their golden fall foliage that would’ve occurred without the damage.
Insecticides are marginally effective since the webworms’ webbing gives them a little protection. When sprays do their job, that can lead to dead caterpillars raining from the tree… not pleasant if the tree is near a walk, patio, or pool.
One bit of good news about this bug – which is true of a lot of bugs, for that matter – is that trouble usually runs in cycles.
Weather and predators help keep mimosa webworms under varying levels of control, contributing to the cyclical nature of the tree-browning trouble.
The bottom line is you can ignore webworm infestations, figuring on them coming and going naturally.
But if you’re having heavy, repeated infestations or just have a zero-tolerance bug policy, the time to spray is June to stop that first generation and August to stop the second one.
Kansas State Extension says effective treatments include the nature-based sprays Bt (Bacillus thuringiensis) and Spinosad and the synthetic-chemical sprays bifenthrin and cyfluthrin.
- More when-to-do-what tips: George’s “Pennsylvania Month-by-Month Gardening” book