By: Phil Reilly, Reilly's Country Gardens
September, 2003
Planting drought-resistant plant varieties in your gardens is a smart strategy for gardening success in our climate-changing environment. However, drought-tolerant plants are not just plant-and-forget plants that have an immediate ability to withstand periods of no water. You do need to give these plants one season of special care while they develop their drought tolerance.
Drought-tolerant plants are usually characterized by having root systems that grow deeply into the soil to 'mine' for moisture in periods of drought. Knowing this alerts you to the need to tend your newly-planted drought-tolerant plants carefully for at least one whole growing season. You have to ensure the plant has the proper soil moisture conditions to develop their deep roots. This means season-long, deep-penetrating watering so that your plants are always actively sending their roots deeper and deeper into the soil. In the second and successive years your drought-tolerant plants will then be more able to live up to your expectations of surviving bouts of drought. But please remember, all plants need moisture at some critical point in a long dry spell. A gardener's role is to be aware of when this critical point has arrived. Plant wilting is a sure sign that water is needed ... NOW!
Nursery customers often ask us "How do you water your gardens?". Our answer - "We water infrequently but deeply". There is no other rule. After the first month of planting new plants, we generally want the top two to three inches of soil to become dry before watering deeply again. It is important to let the surface soils dry out to stress the plants slightly so that they respond by growing deep roots. In other words, each gardener has to be constantly monitoring soil moisture levels to judge when to water. No two soils are alike in their rate of drying so we can't make blanket statements about watering frequency.
We point out that the most important point to remember is to make sure water soaks into the soil deep enough that the soil below the actively growing roots is constantly moist. This reservoir of deep, moist soil is like a magnet drawing roots deeper and deeper no matter how dry the surface soil may be. The worst watering practice is to be stingy with water while any plant is getting established. A plant may look as if it is thriving with regular quick watering, and it may be, but only as long as you keep the surface-growing roots moist. In brutally hot and windy weather, if you miss a day of watering using shallow watering practices, you can easily have shrivelled, dead plants, including your developing drought-tolerant babies, in short order.
Mulching soil with a range of moisture-conserving products is also a wise drought-proofing strategy for any garden. Hay is the only material that we do not recommend as mulch material. Hay often contains a variety of seed-bearing plants. Use hay as a mulch and you will introduce thousands of weed seeds that you'll have to pull up later! Mulch depth is variable depending upon the product chosen. For instance, we use about 3 inches of tree chips, 4-5 inches of straw, or 2 inches of rock mulch on our various gardens. It is advisable to wait until soil temperatures have warmed up (about mid-June around Ottawa) before applying or re-applying mulch. Early-season mulch should be applied making sure that the mulch does not touch the stems of existing plants - this allows air circulation around the plant stems and lower leaves. This air movement helps prevent plant diseases from getting established.
A final moisture-conserving strategy is to slow down wind velocities on your property. Planting hedges and erecting fences will help reduce wind-related soil drying. Gardens located in the most wind-protected areas of your property will be easier to maintain during periods of drought.
What are some good drought-resistant perennials for the Ottawa area? There are many to choose from for sunny gardens but a much smaller choice for shaded gardens. Coneflowers, daisies, ornamental grasses, bearded irises, daylilies, coreopsis, ground phlox, poppies, sedums and most alpine plant varieties are top choices for sunny areas. There are hundreds of varieties of these to fill up any garden. For shade areas look for ground cover plants such as lamiums, ajuga, pachysandra, and epimediums.
