Hot Summer Gardening

Gardening during the dog days of summer

By Carol Papas ©2012
Penn State Master Gardener

For weather watchers (and what gardener isn’t?) 2012 is one for the record books. March both came in and went out like a lamb. It was a banner year for most spring blooming trees and shrubs; their flowers were profuse and long lasting. The record warmth allowed roses and peonies to flower well ahead of schedule. The trend continued and, if your garden is like mine, daylilies and astilbes counted on to carry the garden through mid-summer are long gone. July held a record stretch of 90-degree days; rainfall was scarce, leaving plants and gardeners stressed. A bit of rain and some cooler temperatures in the past few weeks have provided some solace as summer transitions to fall.

There are steps gardeners can take to mitigate the effects of severe heat and drought during the dog days of summer.  If you’re contemplating adding to your garden, do some homework and be sure to choose a plant that will thrive in the existing site conditions.  Keep in mind the proximity of a water source when selecting plants.  If supplemental irrigation is out of the question you must factor drought tolerance into your choice.

Right Plant, Right Place

Once you’ve chosen the right plant for the right place, you can optimize the survival and health of the plant by amending the soil.  There is ample research that the most important step in improving the tilth and biological composition of soil is the addition of organic matter. A compost pile is a gardener’s best friend, providing a source of organic matter to be used throughout the garden.  Alternatively, additives such as leaf compost and well-rotted mushroom manure can be obtained in bulk from landscape supply companies.

Proper Watering

If you choose to water, do it wisely.  Delivering water efficiently can be accomplished with soaker hoses or drip irrigation.  If you are using a sprinkler, try to water in the morning and allow the sprinkler to run until the plants are watered deeply. The general rule is to provide 1 inch of water per week, best accomplished with a single deep soak.  I spent the better part of July dragging hoses around my garden.  My method of measuring the amount of water delivered to a bed is to set an empty tuna can near the sprinkler.  Once the can is full, I move the sprinkler to another section of the garden.  Be observant of the drainage in your landscape and adjust your watering protocol accordingly.  Keep in mind that an emerald green lawn and the lush, prefect gardens pictured in magazines are not entirely realistic during the dog days of summer.

huge watering can

Mulching Can Help

Another helpful strategy to get your garden through the worst of summer is to top-dress beds with a layer of mulch. Mulch conserves moisture, reduces weeds and maintains a more constant soil temperature.  When mulching perennials and annuals, switch to lighter materials, such as compost, soil conditioner or mushroom manure.  Reduce the depth of the mulch to 1-2 inches and avoid piling mulch on the crowns of plants.  Well-shredded leaves make an excellent mulch in woodland gardens.  Vegetable gardeners can use straw or newspaper to good effect for mulch. 

mulch in a wheelbarrow
Shredded wood mulch

Proper plant selection, decent soil, supplemental water and mulch can all be employed to get gardens through the worst of summer weather. By providing optimal growing conditions plants remain healthy and can withstand heat and drought.  Newly planted trees and young plants especially benefit from these strategies.  With proper care roots will make their way into the soil, allowing plants to become established and thrive.

Re-evaluate your Garden

Now is the perfect time to take a good, hard look at your garden and evaluate plants based on their performance after a tough summer.  Perhaps you’re considering replacing a “prima donna” plant with something requiring less coddling.  Consider adding native plants to your landscape. They are adapted to the growing conditions in our area and they have the added benefit of attracting pollinators and beneficial insects to the garden. 


Drought Tolerant Plants

Drought tolerant shade and specimen trees include: red maple (Acer rubrum), sugar maple (Acer saccharum), black gum (Nyssa sylvatica), sweet gum (Liquidambar styraciflua), scarlet oak (Quercus coccinea), pin oak (Quercus palustris) and red oak (Quercus  rubra).  In an established garden consider adding the following tough native shrubs and understory trees: smooth alder (Alnus serrulata), serviceberry (Amelanchier species), chokeberry (Aronia species), pawpaw (Asimina triloba), northern bayberry (Myrica  pensylvanica), sumacs (Rhus species), blueberry (Vaccinium corymbosum or V. angustifolium) and viburnum species (Viburnum acerifolium, V. nudum and V. prunifolium).

pin oak
Pin Oak

Perennials that add personality to the garden and don’t require a full time gardener to spray, stake or divide are the best choices for busy gardeners. Try blue wild indigo (Baptisia australis), with pretty blue flowers in spring, nice looking foliage and lovely seedpods the rest of the growing season. Our native coneflower (Echinacea purpurea) is the current “it” plant of horticulture. The color range has expanded from pink and white to orange, yellow and bi-color flowers.  Many have the added bonus of fragrance.  Aster tartaricus ‘Jin Dai’ is one of the few asters that looks good without pruning, plus it has clean foliage throughout the growing season.


For dry areas near paving low-growing sedums will thrive.  Sedum foliage ranges from gray-blue to burgundy to chartreuse, with pink, yellow and white flowers.  I have used both sedums and low growing herbs, such as thyme and oregano, for a nice tapestry effect in some pretty tough sites, such as a two foot strip between asphalt driveways. Plumbago (Ceratostigma plumbaginoides) and barrenwort (Epimedium species) are good choices for dry areas under trees and shrubs. 

Dragons blood sedum
'Dragons Blood' Sedum

Heading into September, take a good look at your containers.  I like to edit my containers, switching out the tired annuals that have carried the plantings through the dog days. The most readily available late summer annuals are asters, mums and flowering kale.  Cut back larger anchor plants to allow the fresh additions to shine.

Having survived the dog days of summer, gardeners and plants alike can enjoy the cooler days ahead.  If there are areas of your garden that struggled this year, make use of some of the techniques that reduce stress on plantings, add plants that are tough and lower maintenance, and remember- there’s always next year!


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Books for Gardeners


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