After a fairly cool, wet spring, the summer has turned dry and hot quickly at Wellfield. With this weather comes the challenge of providing enough water to garden plants while still conserving water. Most garden plants need approximately 1.0 to 1.5 inches of water per week through the growing season. The gardener must, of course, supply the difference nature does not provide.
We seek to be wise stewards of this precious resource (water), and we utilize several techniques to provide: as much water as a plant needs, where it needs it, when it needs it…and no more.
As Much Water as a Plant Needs
The home gardener should set their irrigation system to run long enough to deliver the required amount of water to the plants. Too much water is a waste; it increases the likelihood of pests and diseases, and it hurts the pocketbook.
To check how much water you are delivering to plants, place some containers throughout the irrigation zone and run the sprinklers for fifteen minutes. Then, measure the amount of water in the containers and the depth of penetration into the soil. This information helps to set the longest run time the zone needs to run in the dry periods of the average Michiana summer season.
It is better to water less often for a longer duration of time. Many people think it is best to water their established gardens a little bit each day. This encourages shallow rooted plant growth, susceptible to greater wilt stress, etc. Watering flower beds or containers deeply and less frequently encourages stronger and deeper root growth.
Where It Needs It
Choose the right delivery system for the situation when deciding how to water the garden. Wellfield’s horticulture staff utilize many different means of irrigation: in-ground systems, hoses, sprinklers, hand watering and drip-irrigation buckets. We rely upon in-ground for the majority of our watering needs, knowing certain areas may need additional, targeted, specific applications for various reasons. Controlling the rate of flow is critical, so water has enough time to get into the root zone. Many people, for example, turn the hose wand fully, blasting container plantings with a quick, torrential down pour. Instead, turn the valve on slightly less than half blast and water slowly, in cycles, providing enough time for water to enter the potting media. The same applies to watering specific plants in a bed system. Water the immediate root zone of the plant slowly, keeping the water where the roots can soak it up.
When It Needs It
The best time to water, in my opinion, is early morning to approximately 10:00 a.m. This allows plants to absorb the most water and reduces the opportunity for foliar disease. Watering in the evening hours, as many people do, though better than mid-day, may allow water to remain on the leaf due to high relative humidity (which often occurs on a summer evening).
Wellfield staff monitor the soil and rain gauges throughout the growing season, adjusting irrigation schedules and amounts, as well as to make the decision if irrigation is needed in the first place. Never irrigate a garden on a schedule (i.e.-I always water this spot on Tuesdays for an hour, spring, summer and fall). The decision to water is determined by soil moisture content. The optimal time to water is just before observed plant stress (usually when soil moisture content is roughly 50% depleted for the portion of soil occupied by the plant’s root zone). In mixed plantings, such as a mixed perennial border, with different types of plants, different sized plants, and different types of roots, different plants will become stressed at different rates. Timing of irrigation of these gardens requires some observation and interaction. Feel or probe the soil to “measure” how moist the soil is while watching for visual signs of stress such as wilting, leaf curl or discoloration. With time, one gets a good sense of when the plants need additional water.
There are a couple of other techniques available to lessen the amount of supplemental water needed in the mid-season periods, and both involve covering the soil. One means is to space plants closer together for quicker “canopy closure.” This shades the soil, reduces evaporation and slows down water, reducing run-off. Many people plant lone plants in a sea of mulch and wonder why they have to water more often. Another way to cover the soil is to add organic matter in the form of compost or mulch. Adding organic mulch covers the soil and improves water absorption. Organic matter holds water like a sponge in the soil, slowly releasing it to the surrounding environment as it dries.
Right Plant, Right Place
Lastly, and most importantly, plant the right plant in the right place. Grouping plants with similar watering needs together, in an area where they will be successful, leads to plants optimally using the water given them.
Josh Steffen, Horticulture and Facilities Manager