The Ornamental Garden in August

  • By Pat Chadwick
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  • August 2017 - Vol. 3, No. 8
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  • 0 Comments

It’s August and many of those beautiful ornamental plants that graced the June and July landscape are just a distant memory now.  This is the month when we rely on tough-as-nails annuals, heat-loving tropicals, and late summer-blooming perennials to keep the garden looking interesting and colorful.   However, the weather at this time of year presents many difficult challenges to the gardener.  August often competes with July for being the hottest, muggiest month of the year in the Mid-Atlantic states.  Needless to say, when we most need it, rain is often conspicuous by its absence in August.   So, rather than sing the blues, what’s a gardener to do?   First, let’s take care of the basics.  Even if you don’t have much in bloom in August, you can improve the appearance of your garden if you:

  • Stay on top of routine maintenance chores such as weeding and watering.
  • Monitor plants for diseases and pests.
  • Deadhead annuals and perennials. Deadheading not only improves the appearance of plants but also encourages some species such as coneflower, garden phlox, and salvia to continue blooming. Keep in mind that some dried flower heads on plants such as tall sedum, globe thistle, astilbe, and coneflower can look attractive throughout fall and winter and you might want to leave them in place.
  • Tidy up daylilies by removing yellowed or dried flower stalks all the way to the ground and all browned or yellowed foliage. Cutting the spent flower stalks back also triggers reblooming daylilies to produce more blossoms.
  • Trim away yellowed or tattered hosta leaves as well as any that have been heavily damaged by insects.
  • Cut back leggy or spent annuals and give them some fertilizer to revitalize them. Within about two weeks, the annuals should produce fresh, new foliage and another round of blooms.

    The Ornamental Garden in August

TIPS FOR CHOOSING HEAT- AND DROUGHT-TOLERANT PLANTS

While it can be challenging to keep the August garden looking fresh and attractive, the job is made easier with the selection of heat- and drought-tolerant plants.   Also, foliage plants can often carry the garden through the month as well as or better than flowering plants.   Some characteristics to look for when choosing drought-tolerant plants include:

  • Display of Drought-tolerant Artemisia, Dicondra argentea, and Salvia species at Longwood Gardens

    Gray or silver-hued foliage – This characteristic is normally a good indication that the plant evolved to withstand drought conditions.  Examples of plants with gray or silvery foliage include wormwood (Artemisia), silver ponyfoot (Dicondra argentea), sea holly (Eryngium), lavender cotton (Santolina chamaecyperissus), snow-in-summer (Cerastium tomentosum), Russian sage (Perovskia), and many succulents and cacti.

  • Closeup of Fuzzy Stachys (Lambs Ear) Foliage

    Fuzzy or woolly-looking foliage – The leaves of many gray or silver-leaved plants may also be covered with tiny hairs, giving the plant a fuzzy, woolly, or hairy look. The hairs reflect solar radiation, which helps to cool the leaf surface. In addition to slowing evaporation, they also capture moisture on the leaf surface and help offset the effects of drying winds.  Plants with fuzzy or woolly-looking leaves include dusty miller (Senecio cineraria), lamb’s ear (Stachys byzantine), silver sage (Salvia argentea), and licorice plant (Helichrysum petiolare).

  • Santolina (Lavender Cotton) with drought-tolerant lace-like foliage

    Small Leaves – A number of drought-tolerant plants have fine or lace-like foliage. The smaller leaf surface area offsets the loss of water through the leaves. Examples include wormwood (Artemisia), beardtongue (Penstemon), lavender (Lavendula angustifolia), rosemary (Rosemarinus officinalis), lavender cotton (Santolina chamaecyperissus) and some salvia species.

  • Succulent display with thick, drought-tolerant foliage

    Thick, fleshy leaves – The cells within the thick, fleshy leaves of some plants, particularly succulents, evolved to store water as a survival strategy during periods of sparse or no rainfall. Many of these plants are also able to store water in their stems and roots. Examples include aloe, Portulaca, Kalanchoe, and sedum.

  • Jade plants in foreground display thick, waxy-coated drought-tolerant leaves.

    Waxy-coated leaves – All plants have a thin waxy coating called a cuticle on their leaves, but those plants that have evolved with a thicker waxy coating are better equipped to retain water by limiting transpiration. Examples include agave, ivy-leaved geranium, camellia, many citrus trees, and some houseplants, such as jade plant and schefflera.

  • Long taproots help these Asclepsia tuberosa plants tolerate drought conditions.

    Taproots – Plants with taproots have a distinct advantage over plants with shallow root systems. When moisture is scarce, taproots are able to penetrate well below the surface of the soil in search of water.   The common grapevine is a classic example of this phenomenon.  It is capable of sending its roots 20 feet down in unrestricted soils.  Other examples of drought-tolerant plants with taproots include butterfly weed (Asclepias), false indigo (Baptisia), globe thistle (Echinops), and fall-blooming Anemone species.

  • Native plants like this Echinacea (Cone Flower) cope well with hot, dry weather.

    Native plants – In general, consider using plants that are native to your geographical area. They have evolved using a variety of strategies for coping with the environmental conditions inherent in that specific region. Examples in central Virginia include beebalm (Monarda), yarrow (Achillea), black-eyed Susan (Rudbeckia), and blanket flower (Gaillardia).

 

WHAT TO DO WHEN THE REALITY OF YOUR ORNAMENTAL GARDEN DOESN’T LIVE UP TO YOUR DREAM FOR IT

The end of the summer is a good time to take stock of how well your ornamental garden is doing.  So take a stroll through your garden and take notes about any plantings that appear:

  • Overcrowded. Sometimes, we fail to take into consideration the mature size of a plant and don’t space it properly when we plant it.  In other cases, a plant may grow well beyond the size listed on the plant tag.  The result is a crowded garden that doesn’t look very attractive.  More importantly, overcrowding is not good for the health and well being of plants.
  • Less vigorous looking than in previous years, have smaller blooms, and are separated or dead in the middle. These are all indications that the plant needs to be divided.  The cooler months of autumn or spring are generally the best time to divide most plants.  However, bearded irises may be divided now that they have stored up energy in their rhizomes all summer.  For information on dividing irises, see Clemson Cooperative Extension’s publication HGIC 1167, Iris.  Daylilies may also be divided in late August.  Just keep the soil moist throughout the autumn while the plants are getting re-established.  See VCE publication 426-030, Daylilies in Virginia for further information on growing daylilies.
  • Marred by powdery mildew and other fungal diseases. Hot weather and high humidity encourages fungal diseases on many perennials, shrubs and trees. Your best course of action is to avoid the problem in the first place by keeping your plants healthy. This means giving them the growing conditions best suited to them in terms of soil, drainage, light, air, and spacing.  Remove, bag, and dispose of diseased foliage, blossoms, and other plant litter that might harbor pathogens capable of re-infecting the plant.  While good information on plant diseases is available from a variety of sources, a Connecticut Agricultural Experiment Station publication entitled “Identification and Management of Diseases of Perennials in the Landscape” provides a good basic overview and photographs of KEY diseases that the typical gardener might face.
  • Damaged by insect pests, such as Japanese beetles, blister beetles, or aphids. It helps to learn the major insect pests and diseases associated with the plants in your garden.  The more attuned you are to the signs of insect damage, the better equipped you will be to diagnose a problem and either prevent it in the first place or treat it before it gets out of hand.
  • Stressed by prolonged heat or lack of water. It’s important to monitor moisture levels at this time of year.  In times of drought, your first priority is to keep newly planted trees, shrubs, and perennials watered.  Woody plants are long-term investments.   Failure to keep them properly hydrated in their first year or two can cause them to struggle for years to come.  Your second priority should be to keep established plantings hydrated.  Your third priority should be annuals, which only live one season.  They are a short-term investment. So, if you’re rationing water, then give annuals bottom priority and don’t feel guilty about it.
  • In need of support. Tie up, cage, or stake any plants that have fallen over. Make a note to stake them earlier next year before they have a chance to fall over.  Better yet, many plants can be pruned back early in the growing season to reduce their height.  They may bloom a week or two later than normal, but pruning will result in shorter stems that may not require support of any kind.

AUGUST INSECTS THAT MAY VEX YOU AND POTENTIALLY STING YOU

WASPS AND BEES

There is a tendency to group all stinging insects under the general category of “bees.”  While there are some similarities, significant biological and behavioral differences exist between the wasp and bee families.  For example:

  • Wasps and their related species are more slender than bees and have fewer hairs on their bodies
  • Wasps feed on other insects, whereas bees primarily feed on plant pollen and nectar.
  • Wasps do not have barbs on their stingers and can sting repeatedly. Bees do have barbs on their stingers.  They can only sting once and then they die.
  • Not all wasps and bees sting. Only the females have stingers.  The males do not.  Bees and wasps that generally sting in defense of their nests may be grouped into a category called “social” bees and wasps.  Because their stings are very painful, this is the group of stinging insects that seem most intimidating to humans.  Wasps belonging to this category include paper wasps, yellow jackets, and hornets.  Paper wasps build gray paper nests that are similar in appearance to a honeycomb when they are viewed from below.  Yellow jackets usually build their nests underground or occasionally in the cavities of hollow trees and buildings.  Hornets build large gray paper nests in trees or shrubs and sometimes under the eaves of buildings.
  • Another category of social wasps includes species that do not sting in defense of their nests. In fact, they rarely sting unless they are being handled. This category Includes spider hunter wasps, cicada killers, and mud daubers, which are all ground-dwelling wasps.
  • The social bees include the major categories of honey bees, bumble bees, and carpenter bees. Honey bees live in colonies and are very social.  Bumble bees are social and nest in existing cavities that are generally in the ground.  They are only aggressive when defending their nests. Carpenter bees are not social and dig solitary nests in the ground.  The female carpenter bee can inflict a painful sting but is aggressive only if handled or molested.
  • Solitary bees, such as sweat bees, mining bees, and leaf-cutting bees, generally nest in the soil or occasionally in natural cavities in wood.

Wasps and bees are among the most beneficial of all the insect species.  They are critical to the pollination of many plants, particularly our food crops.  According to the American Beekeeping Federation, the honey bee alone is responsible for directly or indirectly pollinating one third of all the foods Americans eat.  Because wasps and bees are so important as pollinators, they should be left alone unless they become a menace.

To avoid being stung by one of these creatures:

  • Stay alert when you’re working in your yard or garden, particularly for stinging insects that nest in the ground.
  • Always look before reaching into tall grass, under shrubbery, or into other blind spots where bees or wasps might be nesting.
  • Avoid taking food or beverages outside where you are working.
  • Always wear shoes when working outside.
  • Avoid wearing perfumes or other scented products outdoors.
  • Stay calm if a stinging insect lands on you. Either don’t move or move very slowly and the insect will most likely fly away without harming you.

For more information on stinging insects, see the University of Missouri Extension’s publication G7391 Bees and Wasps or the University of Maryland Extension’s Bulletin 248 Common Stinging Insects:  Wasps and Bees.

BITING MIDGES

Late summer seems to be the time mosquitos and other biting insects are out in full force.  One of the peskiest of these insects is the biting midge, a tiny, blood-sucking fly that is an opportunistic biter of humans and animals alike.  This insect is not to be confused with the non-biting midge, which resembles a mosquito.  The biting midge is not currently known to transmit diseases to humans but it can make you miserable if you’re outdoors when these pests are actively flying about.  Commonly called by the appropriate nickname “no-see-ums,” a bite from one of these diminutive pests can cause a range of reactions in humans, including a burning sensation, small reddish-color welts at the site of the bite, and itching.  Both male and female midges will feed on plant sap and nectar but egg production requires a protein source.  So, the female midge, similar to the female mosquito, obtains protein by consuming the body fluids of other small insects or through a vertebrate blood meal.  That means you and your pet as well as livestock and wildlife.  Only the female midge bites.  The male biting midge does not have mouthparts that are capable of biting. The most effective way to avoid being bitten is to stay indoors when these insects are most active.  Depending on the species, some midges are active during the daytime.  Others are active around dusk and throughout the evening hours.

 

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