August 2002 - Darwin in the
Garden - Dealing with Drought
By Jenny Silver, Master Gardener
Charles Darwin was right. His “survival of the fittest” theory has never been so apt as it is during these water-challenged times. Although Massachusetts has been downgraded from a drought “watch” to an “advisory,” according to UMASS Extension, savvy gardeners are looking at the big picture and focusing on drought-proofing their gardens. This means selecting native, low maintenance, drought-tolerant perennials that can thrive and develop deep, healthy roots despite extended dry spells. Finicky water-guzzlers may be fine for the gardens of Sissinghurst, but here in New England, landscaping with an eye toward water conservation (xeriscaping) is now the norm.
In the early 1980’s an environmental planner in Denver coined the term “xeriscape,” from the Greek word xeros, meaning “dry.” Xeriscaping is the creation of a garden that uses less water than traditional landscaping. This can be accomplished by choosing plants that are drought-tolerant, and by using horticultural techniques that use water most efficiently. The following are basic principles of water-efficient gardening.
Selecting “the right plant for the right place” is at the heart of xeriscaping, as it is at the heart of gardening in general. Avoid mixing plants with high-and low-watering needs in the same area. Plants that thrive in full sun, good drainage, and dry soil should be planted together in southern or western facing areas. Moisture-loving plants should be planted along northern and eastern facing slopes and walls. Think twice about those fussy plant specimens that require gourmet manure teas or are prone to diseases requiring pesticides. UMASS Extension warns, “High frequency watering translates into high maintenance, potential high cost, and overuse of a limited resource.”
For a low-maintenance garden, native perennials are the way to go. Although they will need to be watered regularly during their first year, once established, drought-tolerant perennials maintain their beauty and resilience during the dog days of summer. While other plants look shell-shocked, sedum, lavender, yarrow, day lilies, salvia, and thyme don’t miss a beat during the scorching days of August. These perennials (and those on the list below) require little weeding, watering, fertilizing, or mulching. Plants with taproots and root systems that are sparse or slightly tuberous like peonies, euphorbia, and sea holly are also more adaptable to drier conditions.
Adding organic matter to the soil at the beginning of the gardening season is the most important action a gardener can take to protect against drought. Soil that is rich in humus, such as compost, manure, rotted leaves, or peat will retain moisture and encourage healthier plants that are resistant to drought, pests, and disease. Remember a stressed plant is a magnet for pests and diseases.
Spreading organic mulches up to 2-3 inches helps to seal moisture in the soil, stabilize soil temperature, reduce soil compaction, prevent erosion, and decrease weed production. Mulch should be kept 3-4 inches from plant stems and crowns so that rotting is less likely to occur. Another benefit of organic mulch is that, as it decomposes, it adds nutrients back into the soil. Mulching possibilities include weathered wood chips, dehydrated or aged manures, compost, or chopped leaves.
Watering
Drought-resistant plants have deep roots, but to establish these roots for survival they need to be watered deeply—a least one inch of water per week. Water is even more important to newly planted perennials than established ones. Wetting the top of the ground will only encourage shallow roots. The most efficient watering methods—drip or irrigation systems—provide moisture over a long period of time, with little water lost to evaporation or runoff. Soaker hoses are a less expensive alternative for flower and vegetable gardens. Morning is the best time to water, so that foliage can thoroughly dry and be less susceptible to mildew or other diseases. UMASS Extension recommends not trying to water all planted areas at each watering. Better to saturate a targeted area and then allow it to dry out before watering again.
Keeping weeds down to a minimum will also help with water efficiency, since these voracious garden thugs bully established plants for any available moisture. In addition, proper pruning, division, pest control, and fertilizing will also help keep most drought-resistant plants happy and thriving.
UMass Extension suggests the following perennials and annuals:
Perennials: Butterflyweed, Anise hyssop, Amsonia, Artemesia, Asters, False indigo, Perennial bachelor’s button, Coreopsis, Pinks, Cone Flower, Barrenwort, Globe thistle, Sea holly, Spurge, Blanket flower, Bigroot geranium, Hellebore, Daylily, Common mallow, Hosta, Siberian iris, Lavender (not hardy in all areas), Gay feather, Catmint, Peony, Russian sage, Phlox, Black-eyed Susan, Sage, Sedum, Hens and chicks, Lamb’s ears, Thyme, Mullein, Yarrow, Yucca
Annuals: Pot marigold, Canna, Ornamental peppers, Cockscomb, Spider plant, Cosmos, Foxglove, California poppy, Gazania, Sunflowers, Strawflower
Wise gardeners understand that the amount of rain that falls is beyond their control. Within their control, however, is the creation of a garden that can withstand the rigors of drought without sacrificing beauty and variety. Or, as Darwin might say, for droughty times, drought-resistant plants are the natural selection.