This is NOT the time to put in new plants
Do not attempt to establish new trees or shrubs or move existing perennial plants around during these searing heat waves. It’s almost impossible to keep new plants alive in this kind of weather, which could well return for a couple more rounds after the next stretch of less deadly temperatures.
But the good news is that the absolute best time to plant new trees and shrubs is not far off. After the heat breaks in September, it will be the ideal time to put new trees and shrubs in the ground. In fact, trees and shrubs planted in the fall have a much better rate of survival than the same plants installed in the spring.
Plants that are put in the ground in the fall enjoy pleasant weather while they establish, then they go nicely dormant. Plants installed in the spring often have to quickly deal with the stress of summer heat on top of transplant shock.
You generally get a better deal at nurseries and garden centers in the fall. They want to get the plants out before they switch over to the holiday seasonal stuff.
Don’t kill your lawn right now
This has been a harsh summer for cool-season lawns of fescue, rye and/or bluegrass (the most dominant lawn grasses in the region), which love spring, winter and fall but struggle to survive the summer. These grasses originally come from cooler climes, such as England, Ireland and Scotland, and surviving a D.C. summer is just not in their DNA.
To help them out:
- Do not cut them during dry heat waves.
- Never cut them lower than 3 inches for any reason.
- Always leave the clippings behind to help shade the soil and provide much-needed organic matter.
- When you water, water deeply for several hours at a stretch, to really saturate the soil.
- You can water deeply like this twice a week during heat waves (in normal weather, just once a week is ideal and only if we haven’t gotten an inch of rain recently).
- Do not water more frequently or for short periods of time. Bad watering encourages the shallow root systems that make lawns much more vulnerable to summer heat.
- Water only in the early morning; never in the heat of the day (the plants are closed up tight to retain what moisture they already have) or in the evening when the grass will stay wet overnight (which breeds disease).
- Most importantly: Do not feed your lawn in the summer. Summer feedings are not a feast. Instead they are a recipe for dead, desiccated grass.
Caterpillars that camp in trees
Sue Ann in Boyds, Maryland, sent a picture of what looks like giant pantyhose covering the bottom branches of a tree and asks, “what is this? It’s in our neighbor’s tree and seems to be spreading over the entire neighborhood. Will this hurt the trees and what do we do about it?”
It’s a huge infestation of fall webworms, Sue Ann. These are caterpillars that build giant (and extremely ugly) communal nests on the branches of trees. Although incredibly unattractive, the actual caterpillars don’t cause any long term harm to the trees because it’s the end of the season and the trees have already absorbed all the solar energy they need for the year. So the little beasts eating their leaves don’t matter much.
But it’s really ugly so get rid of them anyway.
Step one is to make a clean sweep. Your first course of action when you discover webworm nests (or the similar tent caterpillars in the spring) is to simply bust up any nests you can reach with a broom, hoe or long pole. This will expose the caterpillars inside to hungry birds, who will feast on your foes.
Step two is the great organic caterpillar control. After you have fun playing Whack-a-Worm with the low hanging nests, spray the rest of the tree with the original form of Bt (also known as BTK). Sold under brand names including Dipel, Thuracide and Green Step, Bt is incredibly safe to use. One of the oldest organic pest-controllers, it’s been in use for many, many decades.
Based on a naturally occurring soil organism, Bt is deadly to caterpillars that eat the sprayed leaves, but it has no effect on pets, people, frogs, toads, bees, birds or even butterflies. Bt only affects caterpillars, and it only affects caterpillars that eat plant material that was sprayed with the Bt. It is remarkably specific, making it one of the safest pesticides on the planet.
The product label will specify that the active ingredient is Bt, BTK, or it will use the full name: “Bacillus Thuringiensis, variety (or stain) Kurstaki.”
BTK was the first strain of Bt to be isolated, so it is often just called “Bt.” But over the years many other strains have been isolated and marketed, including the hugely important BTI. Sold in the form of doughnut-shaped dunks and granules, BTI is the most effective way to prevent mosquito breeding in standing water.
It’s important to note that the Bts are not interchangeable. BTK has no effect on mosquitoes and BTI won’t stop caterpillars.
Webworms prefer weak trees
The immediate cure when caterpillars go camping in your trees is to break up the nests you can reach and spray the organic caterpillar control Bt on the rest. But the currently active fall webworm, and their look-alike (and much more destructive) springtime cousins, tent caterpillars, are mostly attracted to trees that are stressed and already weakened.
One big cause of such stress is mulch piled up against the bark of the tree. Yes, you see it everywhere. And it is wrong everywhere. “Volcano mulching” rots the bark by keeping it moist, and it makes possible much unseen mischief by insects and vermin like mice and voles. If you have mulch piled up against the trunks of your trees, hoe it away from the bark before it’s too late.
The proper way to mulch a tree is to start about 6 inches away from the trunk, then have a one-to-two-inch thick layer of your chosen material going out in a circle as far as possible. Compost is the best mulch. Pine straw looks great and arborist wood chips (like you’d get from a tree-trimming crew) are fine. Avoid bark mulches and never ever used dyed mulch. Lord knows what that coloring is covering up.
Proper mulching protects trees from mower damage, keeps weeds down and retains soil moisture in the area of the root system, which spreads out like an umbrella underground. There is no logical reason to ever have mulch touching the trunk of a tree and there are about 147 reasons not to do so.
Mike McGrath was Editor-in-Chief of ORGANIC GARDENING magazine from 1990 through 1997. He has been the host of the nationally syndicated Public Radio show “You Bet Your Garden” since 1998 and Garden Editor for WTOP since 1999. Send him your garden or pest control questions at MikeMcG@PTD.net.
