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Drought Tolerant Thoughts
by Marg Fleming
by Marg Fleming

1979 - BSc. Botany University of Toronto, 1981 - MSc. Forestry University of Toronto, 1982-1986 - Horticulture Teaching Master - Niagara College , St. Catherines Ontario., 1986 - 2000 - Owner/Operator of Cedar Valley Botanical Gardens - Brighton Ontario, 2000- Present - Manager of Horticulture Toronto Zoo

Public Speaking Topics - Perennials, house plants, garden design

November 21, 2004

Hot dry weather has persisted this year, compromising many of our reliable perennials and annuals. But some plants thrive in this heat and should be afforded several prominent areas in our borders in anticipation of the next drought year. Here are some reliable drought resistant plants to consider.

Evergreens of all types are designed to resist drought. Long thin needles expose a small surface area to the hot desiccating wind, so less moisture is lost. Besides, the sap of conifers is thick thereby resisting evaporation. Also, the breathing pores of the needle-like leaves are recessed in troughs along the needle. This minimizes exposure of this access to the leaf interior. A tough waxy layer coats each needle, further reducing the risk of moisture loss.

After a dry summer, specimen evergreens should be given a thorough drink of water before winter to ensure a healthy recovery next spring. By leaving the hose dripping on the root system for several days, an adequate amount of water can be delivered to the needy roots with focussed penetration.

Clump grasses are very drought resistant. Though in a dry year they will abbreviate their height and in some cases reduce their flowering stalks, clumping grasses provide a stunning shock of unusual texture in a late summer border. Try perennial Fountain Grass (Pennisetum sp. ) with its foxtail-like blooms. Tall Blue Oat Grass (Helictotrichon sp.) displays its icy cool blue leaves all through the summer’s heat. Fine, diaphanous blooming stalks emerge to five feet above the 2 1/2 foot clump. By dragging a lawn rake through the clump next spring, all the old leaves can be quickly extracted to expose the frosty new growth.

Reed grass (Calamagrostis sp.) is an elegant clumping grass that supports tall lacy flower stalks as late summer descends. Though these clumping grasses are very well behaved, occasionally a fertilized seed or two may detach and initiate a brand new clump not far from the parent. These are easy to weed out, or they provide a neat, compact plant for passing along to gardening friends. Alternatively, perennial grasses are easy to lift and divide for installing portions at other venues in the yard. Do it in spring when rainfall is plentiful and cool temperatures favour growth.

With the trend in natural landscapes becoming more popular, try Big Blue Stem or Little Blue Stem, both native grasses that have blue leaves. These native clumping grasses have a less cultivated appearance, but they are tough and reliable in the summer heat.

Shade gardens tend to suffer in the absence of irrigation. The very trees providing the shade take the lion’s share of moisture making it difficult for plants beneath to make ends meet. Some drought tolerant species may be required to cope with these exceptional conditions. Baltic Ivy creates a thick green groundcover that defies drought and shields the soil from excessive moisture loss. Sensitive fern is an attractive native shade plant that thrives in both dry and moist soil. Its attractive atypical bold fronds provide some green understory when other more vulnerable plants may have taken early retirement.

All of the Sedums are very heat/drought tolerant. They come in a vast variety of leaf colours and shapes from blue Burro’s Tail (Sedum reflexum) to red Dragon’s Blood (S. spurium). Hen and Chicks (Sempervivum spp.) scoff at drought and can even be brought indoors as a houseplant for winter. Alternatively these virtually indestructible cactus-like plants can remain outside year round. Hen and Chicks species vary in leaf colour and plant size so the field of interest in a dry border can be quite broad.

Showy stonecrop is the perennial, drought-tolerant equivalent to fall mums. White, red, or pink, showy stonecrop (Sedum spectabile) is a prolific and attractive specimen to include in borders for reliable fall colour.

Keep these plants in mind even as fall rains wash away memories of summer drought. By incorporating some of these drought-tolerant species into our gardens this fall, we can respond to drought with adaptable, colourful, and drought-defiant plants.


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