What dreadful hot weather we have! It keeps me in a continual state of inelegance. ~Jane Austen
We have gotten a few days of hot summer already and we know more is coming. Seems like a good time to talk about water conservation in our gardens.
First, a little botany. No matter how fertile the soil, plants will not be able to use the nutrients if the ground doesn’t have enough saturation. That’s because the nutrients are dissolved in water which the plant uptakes through its roots from where it flows to the leaves (and fruit) drawing out the nutrients. The water then is released through the stomata (tiny holes in the leaves) in a process known as “transpiration”. Dry soil, hot air, low humidity and wind will cause the stomata to close which not only stops the flow of nutrients but limits the ability of the plant to cool itself, since water release is a cooling action.
Most garden plants need 1-2 inches of water each week. It is best provided early mornings (to reduce evaporation and risk of fungal stress.) One to two deep soakings per week encourages deep root growth. Watering amounts should be consistent and regular. Too little and plants will respond with bolting (an attempt to quickly produce seed before dying). Too much can cause damage to the root system. Erratic watering can cause cabbages to split or blossom end rot in tomatoes, for example.
On any given day, there will be a range of watering needs depending on the type of plant and its stage of growth. Limiting watering to those plants most in need is a good conservation practice. Water is most critical during seed germination, the first few weeks of development, immediately after transplanting and during flowering and fruit production. “Fruit” can mean apples or pears but also can mean peas, cabbages, beans, etc—essentially the part of the plant you eat that is not leaf or root.
Another strategy is to incorporate plants which are inherently low water consumers such as herbs, swiss chard, lima beans, jerusalem artichokes, okra, peppers and asparagus. Or, choose seed from plants bred to have drought resistance, for example: Hopi Pink corn, Jackson Wonder lima bean, Green Striped cushaw squash, Iroquois cantaloupe, Armenian cucumber, Pineapple tomato….You can also use varieties with either: short days to maturity or, miniature varieties such as mini peppers or mini eggplants.
Of course, garden beds with good structure and good drainage most effectively use the water available. Planting on level ground prevents wasteful runoff and incorporating organic matter provides additional air space for improved drainage. Digging or tilling the soil as deep as possible before planting preconditions the soil for the roots to be able to spread out and down with ease.
Laying out a garden in raised beds rather than rows also helps reduce water needs because of improved soil texture and because the more intensive planting reduces the non-productive areas (such as rows). Typical raised beds are 3-4 ft wide to allow for easy access from either side. Some people plant in blocks of 3-4 ft for full perimeter access. The block system lends itself well to growing plants with similar watering needs together: example, cukes, zukes and squash.
Speaking of cucumbers, I find they like to grow in semi shade and so I choose companion plants such as okra, corn, amaranth or buckwheat to provide this and also protect the understory crop from drying out. Similarly, windbreaks of any kind will help reduce evaporation and maintain good moisture levels in both the leaves and the soil.
And mulch….I cannot overpraise mulch! Not only does it retain soil moisture, but it controls weeds which compete for water. Its light color also reflects the intense summer heat to keep soils a little cooler and less likely to dry out. Mulch is part of any good soil improvement plan as it breaks down readily to provide organic matter. A charcoal known as Biochar is becoming a popular soil amendment as the highly porous charcoal retains water and releases it when soils dry out.
Using drip or soaker hoses reduces water use by up to 50%. Keeping water pressure low and targeting water to the plant (rather than the walkways) is always useful. Likewise, getting annuals planted before the hot and dry days of summer allows them time to establish a deep and expansive root system to survive the hottest days.
In closing, I invite all you gardeners to experiment with some rainwater catchment to really take your water conservation efforts to another level.
Gigi Wahba is a devoted organic gardener with a deep appreciation for the wonders of nature. She also manages the Memphis Farmers Market which runs Thursdays 3-6pm at the Courthouse Square.