For weather watchers, 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 daylilies and astilbes counted on to carry the garden through midsummer 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, 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. If you're considering adding shrubs or ground covers under the canopy of a tree, be aware that the tree will grab the lion's share of moisture within the drip line of its branches.
Pittsburgh's hilly terrain does not allow water to percolate into the soil as easily as it will on flat ground. Other situations that deplete soil moisture include: long exposure to late-day sun, sites impacted by drying winds, and plantings adjacent to large expanses of paving, buildings or hardscape.
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 adding 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.
If you choose to water, do it wisely. Use 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.
Another 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.
Proper plant selection, decent soil, supplemental water and mulch can all help to get gardens through the worst of summer weather and allow plants to withstand heat and drought.
Now is the perfect time to take a good, hard look at your garden and evaluate plants based on their performance this summer. Perhaps you're considering replacing a "prima donna" 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.
Drought-tolerant shade and specimen trees include: red maple (Acer rubrum), sugar maple (A.saccharum), black gum (Nyssa sylvatica), sweet gum (Liquidambar styraciflua), scarlet oak (Quercus coccinea), pin oak (Quercus palustris) and red oak (Q.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).
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 wild indigo (Baptisia australis), which has pretty blue flowers in spring, nice-looking foliage and lovely seedpods the rest of the growing season. Aster tartaricus 'Jin Dai' is one of the few asters that looks good without pruning, plus it has clean foliage throughout 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. An excellent overview of the many new coneflowers available can be found at: www.mtcubacenter.org/images/PDFs-and-SWFs/Mt_Cuba_Report_Coneflowers_for_Mid-Atlantic.pdf.
For dry areas near paving, try low-growing sedums. The 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 2-foot-wide strip between asphalt driveways. Plumbago (Ceratostigma plumbaginoides) and barrenwort (Epimedium species) are good choices for dry areas under trees and shrubs.
Heading into September, take a good look at your containers. I like to edit my containers, switching out the tired annuals. 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.
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!
Carol Papas is a Penn State master gardener. Columns by master gardeners will sometimes appear in place of the Garden Q&A by Sandy Feather, a Penn State Extension educator.