Things not to do when it’s super-hot outside

Nursing the yard through a hot summer sometimes is more about what you don’t do than what you do.

Some activities are wasteful, some are counter-productive, and a few are downright plant-harmful when temperatures sizzle in the 90s.

June’s string of seven straight 90-degree-plus days could be just a harbinger of what’s to come, given that July and August are central Pennsylvania’s historically hottest two months.

Here are five yard jobs to put off when the heat’s up – especially when it’s dry.

1.) Don’t mow the lawn. When grass stops growing in a hot, dry spell – even if it’s a little long at the time – keep the mower in the shed.

Longer blades are a benefit because they shade the soil, both keeping it cooler and helping to retain moisture. If you cut them, grass blades also will lose moisture faster and go brown faster.

Wait until temperatures cool and a decent rain happens to mow again.

2.) Don’t fertilize. This includes most trees, shrubs, evergreens, and perennials, as well as the lawn.

For one thing, heat- and drought-stressed plants don’t use much (if any) fertilizer during a hot, dry spell.

For another, the salts in fertilizers can hasten the effects of drought stress and injury.

Exceptions: it’s OK to keep fertilizing container plants, vegetable gardens, annual flower beds, and other actively growing plants that you’re watering regularly.

3.) Don’t prune. As with mowing, fresh plant wounds increase the amount of precious moisture leaving the cut foliage and stems.

Pruning can also encourage new growth, which is counter-productive when plants are in survival mode and trying to protect and conserve instead of invest moisture on new growth. Tender new growth is also more susceptible to heat injury.

Dead wood can be removed from trees and shrubs, and so can damaged or ratty foliage on the perennials. But wait until cooler, damper times to cut back shrubs, prune hedges, and do any other extensive pruning work.

If you absolutely must prune, water well afterward and again so long as it stays hot and dry.

4.) Don’t spray – especially on hot, sunny days. For one thing, the adherence agents and oils in most liquid pesticides can heat enough in the summer sun to damage plant foliage.

Second, herbicides and insecticides sometimes can do unintended damage to plants that are under heat stress.

And third, even granular lawn and garden pesticides can be less effective above certain temperatures.

Check the labels for application warnings. You might be surprised to see how many products advise not to apply when temperatures are more than 85 degrees.

If sprays are needed before a cooler spell happens, at least wait until evening to apply.

5.) Don’t plant or transplant. It’s possible to plant new plants or move wayward ones in summer, but it’s not the best time. Survival odds go down as the temperatures soar into the 90s, and you’ll be more on the hook to keep the soil damp in those early weeks.

This goes for grass seed, too. You can get grass up and growing in summer, but it’s much more of a watering challenge than if you wait until right after Labor Day.

If you must plant/transplant in summer: 1.) do it in the evening or during a cloudy spell, and 2.) be ready with the hose to keep the soil consistently damp afterward.

Ways to reduce outside water use

Heat drives up a plant’s water demands, so it’s no surprise that July and August are two peak months for outdoor water use. Higher water bills prove it.

Some of the use is unavoidable, i.e. to keep new trees alive and the vegetables from frying before they make it to harvest. But gardeners sometimes end up applying more water than necessary.

One fast way to save a lot of water in summer is by letting the lawn go brown and dormant when that’s what the weather dictates. Otherwise, healthy lawns can survive at least three to four weeks in this dormant state and will quickly “green up” when rain returns.

If a drought drags on longer than that, just a quarter-inch of sprinkler irrigation per week is enough to keep the crowns alive. More than that and you’ll bring the lawn back to life needlessly when it’s trying to do what it needs to do to survive a challenge naturally.

Keeping lawns green in a summer dry spell is mainly a cosmetic issue that sucks up more water than any other landscape use.

“Extensive lawns appear to be the main driver of over-irrigation,” concluded Washington State University horticulturist Dr. Linda Chalker-Scott in a recent paper on landscape water use for the Journal of Environmental Horticulture.

Chalker-Scott offers these four tips for conserving water:

1.) Substitute fresh water with recycled/reclaimed water, such as rainwater collected in rain barrels and “graywater” from sinks, air-conditioner condensate, bathtubs, and washing machines.

That water is best used on ornamentals, but if you use it on edibles, be sure to wash the harvest well before eating, Chalker-Scott says.

2.) Avoid overfertilizing plants, which speeds up growth and increases water demand. If plants are growing and blooming well, that’s a sign they’re getting enough nutrition.

3.) Consider replacing lawn space or high-water-demand annual flowers with trees, shrubs, groundcovers, and drought-tough perennials, which need little to no supplemental watering.

4.) If you’re using automatic irrigation, invest in smart sensors or turn off the system when the soil is adequately damp. And be sure you’re irrigating only planted areas, not wasting water on driveways and sidewalks.

The National Garden Bureau offers three more ideas:

1.) When planting a new bed, improve the soil with organic matter to encourage deep root growth, lean toward drought-tolerant species, or group plants by their water demands to better direct water only when and where it’s needed.

2.) When you water, water directly into the soil, not over the plants. That both reduces the incidence of leaf disease and reduces moisture loss to evaporation (which can hit 30 percent loss on a hot day). Drip irrigation is particularly efficient.

3.) Keep bare ground covered either with vegetation or mulch. That also reduces evaporation loss from the soil.

And Colorado landscape designer Paige Payne adds these two:

1.) Plant densely to keep bare ground covered without the need to continually mulch. “You don’t want overplanting, but having space filled with plants is ideal,” she said in a Great Grow Along webinar on wise water use.

2.) Consider more hardscaping features, such as stone paths, paver patios, and boulders as ornamentation. “These minimize water use, provide functional elements, and add aesthetic appeal,” Payne says.

Are Japanese beetle traps a good idea?

July is peak time for Japanese beetles, those hard-shelled, coppery-colored bugs that chew the leaves of roses, grapes, hollyhocks, cherry and linden trees, and some 300 plant species.

To combat the masses of them, many homeowners set out beetle traps that use pheromones (hormonal scents) to draw beetles into mounted bags from which they can’t escape.

Although lots of beetles end up in these traps, research at the University of Kentucky found they attract many more beetles than are actually caught.

“Consequently, susceptible plants along the flight path of the beetles and in the vicinity of traps are likely to suffer much more damage than if no traps are used at all,” Kentucky Extension advises in a tip sheet on beetle control. “In most landscape situations, use of Japanese beetle traps probably will do more harm than good.”

That gives rise to the advice that if you’re going to use traps, either place them well away from plants or give them to all of your neighbors.

“I guess it’s really hard for people to understand when they have this bag with a writhing mass of maybe 4,000 or 5,000 beetles in there that they haven’t done something good,” adds Ohio State University’s “bug doc” Dr. Dave Shetlar. “Beetles hit those yellow vanes, and for every beetle that gets in the bag, there’s a beetle that hits the yellow vane and lands on the turf below. They’ll usually then get up and fly over to your ornamental plants.”

An alternative way to control Japanese beetles, if they’re getting out of control and you’re patient, is to hand-pick them and drop them in a container of hot soapy water.

Neem oil is an organic spray that’s effective in killing and repelling them for three to four days per spray, says Kentucky Extension.

And to kill them with conventional insecticides, lots of those are effective for beetle control, including cyfluthrin, bifenthrin, permethrin, and carbaryl.

Another anti-beetle strategy is to prevent next year’s beetles from hatching. This month’s flying adults will lay eggs in the coming weeks that will hatch into fat, creamy-white, caterpillar-like critters called “grubs.”

Grubs feed on lawn and plant roots into early fall (often killing patches of turfgrass in the process), then overwinter several inches deep in the soil before pupating into adults next June.

Shetlar (who likes to call these grubs “land shrimp”) says the first half of July is an excellent time to apply granular grub-preventing products to the lawn. Most contain imadacloprid (Merit).

When watered or rained in, grub preventers kill grubs soon after they hatch, limiting the following year’s beetle population.

One blessing of a very dry summer is that it also discourages the hatch of Japanese beetle eggs. Look at it this way: the lawn might go brown, but at least it should mean less beetle trouble next summer.

• More when-to-do-what tips: George’s “Pennsylvania Month-by-Month Gardening” book