The August To-Do List

Will this hot, dry weather continue in August?  That’s the question I ask myself every day.  As I write this, the National Weather Service is predicting that the answer to my question will be “no” — and that’s grounds for celebration.

I only recently discovered HOW to try to answer the will-it-ever-rain question, and now I’m hooked.  The National Weather Service has a division called the Climate Prediction Center, and it issues long term predictions for temperature and precipitation, among other things.  These predictions come in the form of U.S. maps with regions shaded to indicate the probability that temperature and precipitation will deviate from the norm for a given time period.  The 6-10 day Outlook, for example, illustrates the  probability, that the observed total precipitation, over the upcoming days will be either below normal (B), median (N), or above normal (A).  Take a look at the Temperature and Precipitation Outlook for August 4–8,2021 at 6-10 Day Outlook/Climate Prediction Center/NOAA.gov.  These graphic maps are revised periodically, so by the time you read this, it may have been revised, but at the moment, a slight chance of above-normal rainfall is predicted for early August.  Before we start cheering, keep in mind that these long term forecasts are labeled as “experimental” — a cautionary term indeed.

Watering may very well be your main task this month.  If your water supply becomes limited due to restrictions or because your well is not adequate for the demands upon it, you’ll need to prioritize the water needs of recently-planted trees and shrubs (those planted within the last 1-3 years).  To avoid any waste, be sure to water early in the morning or late in the evening.  which reduces the amount lost to evaporation and gives plants time to replenish.  “Water early in the morning to allow plants to get moisture before dealing with the hot day or water late in the evening to allow plants to replenish after the day.” “Heat and dry weather pose problems for landscape plants,” Va.Tech,2020

If we continue to suffer periods of above-average heat and drought, you may start to wonder, as I did in July, if there’s anything that a gardener can do to help their plants survive — other than watering. Could some extra nutrients help?  I was surprised to discover that the answer to that question is no.  Why? Fertilizer encourages new growth, which will in turn, increase the plant’s need for water.   Here’s the complete list of do’s and don’ts to help your garden survive drought:

Tips for Mitigating Drought and Heat Stress on Landscape Plants:

• Do NOT encourage growth:  no fertilizing, and no pruning (except to remove dead or dying branches).
• Add mulch around individual plants, as much as 3-4″.
• Remove weeds, which are competing with garden plants for moisture.
• Deadhead flowering plants early. Do not allow spent blooms to form into seeds. Plants going to seed use large amounts of energy and water, which is best used to maintain plant health during the dry period.
• Avoid using pesticides and herbicides. Applying an herbicide when it is too hot may turn the liquid into gas, which could cause drift onto your already-suffering garden plants. Also, weeds do not take up the herbicide as well during dry conditions.  When it’s hot and dry, pesticides can injure plants.

For a deeper understanding of how drought impacts trees and shrubs, I highly recommend “How Dry Seasons Affect Woody Plants,” University of Kentucky/Coop.Ext./ID 89.

Since the National Weather Service is predicting an increase in precipitation for August, I have high hopes that we gardeners will be able to proceed with our usual seasonal tasks this month.  A good place to start your to-do list is the Monthly Gardening Tips/August  in the Gardening Resources section of the website.

Deadheading will encourage new flowers on a number of plants, such as coneflower, garden phlox, salvia, asters, rose campion, and anise hyssop.  If you have reblooming daylilies, cut back the spent flower stalks and snip off any seedpods to trigger the growth of new flowers.

If you are pinching off spent canna blooms, be careful. New buds usually form right next to the spent flowers. Some canna lilies produce big black seed pods, while others are sterile. Watch to see if seed pods develop. If they don’t, deadheading the flowers isn’t necessary, except for aesthetics.

Monitor for Diseases and Pests

Are you seeing more damage from pests and diseases?  Drought and heat can render a plant more susceptible to both.  Monitor regularly to stay on top of these issues.  Removing diseased foliage as soon as you spot it can prevent spread.  And a number of pests can be removed simply by handpicking or spraying them off with water.  The water spray method works on both aphids and spider mites.

I just knocked a huge herd of spider mites off of my purple coneflowers, but the experts say this must be repeated frequently to keep the mites from climbing right back up the plants. Mid-season washing of the leaves can help reduce the potential for spider mite population booms.

If mites are well-established, you might be tempted to try a pesticide, but most insecticides are not effective on mites, and some, especially carbaryl, result in increased mite damage after their natural enemies have been killed.  If you’re desperate, you might consider either an insecticidal soap or horticultural oil, which are designed to coat the mite’s exoskeleton and cause suffocation. Unfortunately, these products can also kill beneficial mites and insects upon contact, though they do not have residual impacts.  For more information on spider mites, see Integrated Pest Management for Spider Mites, Clemson Coop.Ext.

Hot weather and high humidity encourage fungal diseases on many perennials, shrubs, and trees.  Remove, bag, and dispose of diseased foliage, blossoms, and other plant litter that might harbor pathogens capable of re-infecting the plant.

If you’re struggling to diagnose a problem, there are a number of sources that can help.  For a comprehensive guide to diagnostic websites and apps, be sure to start with the Garden Shed article  “Oh, No! Something’s Wrong with my Plant!” .   If you’re wondering what’s wrong with a perennial, check out the Connecticut Agricultural Experiment Station publication entitled “Identification and Management of Diseases of Perennials in the Landscape,” which provides a good basic overview accompanied by photographs of KEY diseases that the typical gardener might face.  If it’s a tree or shrub you’re concerned about, this Penn State article can help you in narrow down the possible diseases and pests based on the type of injury you’re seeing: Penn.State Ext/Diagnosing Injury to Woody Ornamentals.  Once you have a suspect or two, you’ll find photographic guidance for many diseases and pests  at the Plant Problem Image Gallery maintained by the Va Tech Plant Disease Clinic.  In addition, Virginia Tech has a number of videos about common plant diseases, and you’ll find these at this YouTube/VCE Master Gardener link.

If you’ve got a mystery disease and need expert diagnostic help, you’ll be happy to know that the Virginia Tech Plant Disease Clinic has lifted its Covid restrictions on submitting samples of plants for analysis.  Read about how to submit both photographic and live plant samples at https://spes.vt.edu/affiliated/plant-disease-clinic/submitting-samples.html.  Contact the HELP DESK for details on getting your sample into the office and on its way to Virginia Tech.  Call 434-872-4583 or send an email to albemarlevcehelpdesk@gmail.com.

To see a list of pesticides recommended by Virginia Tech scientists for each major plant disease — including organic and biopesticides, — see Table 4.1, Control of Ornamental Diseases, Pest Management Guide 2021.

August and September are good times to attack invasives like Japanese stiltgrass and autumn olive — before they drop seeds.  Read about how to deal with autumn olive and Japanese stiltgrass and other invasive plants at the very helpful website of Blue Ridge Prism. Blue Ridge Partnership for Regional Invasive Species Management or PRISM is a Cooperative Weed Management Area serving Albemarle and several other area counties.  If you’ve got invasive problems, you may want to sign up for their newsletters or one of their training sessions.

Managing your lawn during a drought can be tricky.  Should you let your lawn go dormant for a while?  Consult the expert guidance of Virginia Tech via this podcast and article:  Lawn Management During Heat and Drought/Va.Coop.Ext.

Be sure to take a break now and then to enjoy your garden.  And while you’re at it, make some notes about which plants are doing well and where you’d like to add some more drought-tolerant plants in the fall.  Climate change is turning us all into citizen scientists in our own yards as we learn from our own observations which plants can withstand the hotter, drier conditions of our summers.

SOURCES:

“Heat and dry weather pose problems for landscape plants,” VTX.vt.edu/articles (Aug. 2020)

“Keeping Your Plants Healthy:  Dealing with Dry soils and Drought,” University of Wisconsin Ext., (6/11/2021)

“Mitigating drought stress on landscape and garden plants during the current local dry spell,”  Kenosha.Extension.Wisc.edu

“Dealing with Drought,” NC State Ext.

“Gardening Tips During a Drought,” S.Dakota Extension

“Diagnosing Plant Problems,” Va.Tech/Educational Resources No. 426-714 (2018)