The composition of some plants is as much as 90 percent water, and moisture around the roots is key to the absorption of nutrients and other minerals. When water is scarce, the plant draws water from its cells, causing the cells to shrink and making the plant wilt. In many cases, watering will restore the cells and the plant looks normal. If left to wilt too long, the plant cannot restore water to its cells and eventually dies.
The early morning is the best time to water because this allows the cool plant to absorb as much water as it can before the heat of the day. Cool evenings are similarly appropriate, but be sure not to get the foliage wet, as it will have a hard time drying off and many plants are susceptible to diseases due to wet foliage.
Trees and shrubs
To determine the best ways to water, consider the plant’s long-term health. For the first two years after being planted, trees and large shrubs require slow watering. This can be done with a hose on a slow trickle, though several hours are needed when watering a tree. An alternative is to drill 5 to 9 small holes into the bottom of a 5 gallon bucket, set the bucket on the tree root ball, and fill it with water. Another option, the Tree GatorTM, holds up to 20 gallons, wraps around the tree trunk, and slowly drips water for 6 to 10 hours. Keep in mind that when using the hose or a bucket, you still have to water both sides of the root ball.
Rest of the garden
The rest of the garden, including perennials, annuals, groundcovers, vegetables and herbs, should get about an inch of water a week. The best way to achieve this is with a hose and a water breaker. Water breakers are water nozzles similar to showerheads that deliver a moderate spray of water, just like a gentle rain. Nozzles that deliver a strong stream should not be used. Before you put the hose away, check the moisture level by sticking your finger into the soil. When the whole length of your finger comes up muddy you are done. Annuals tend to need more water, as they are not root established until later in the growing season, but check the root ball before watering.
Container gardens can be watered with a watering can or the hose. When using a watering can, it’s easy to assume that one can is enough, but containers, due to the density of soil and roots, need watered more often than the plants in the garden. You need to make sure the entire root ball of a plant is wet. Pour enough water into the container so that it sits on top of soil, letting the soil soak in the water. Go back and water again in this manner a number of times. The extra water will flow out the drain holes in the bottom. If the container is small enough to be moved, put a couple of inches of water in a larger watertight container and set the container into the larger one, letting the soil soak in the water through the drain holes.
Cool season grasses like Kentucky Bluegrass, Tall Fescue, Fine Fescue, and annual and perennial Ryegrass, do poorly in the hot, dry summer months. These grasses even turn brown and go dormant during the extreme heat and dryness of summer. No amount of water from a home sprinkler can turn dormant grass green again; that’s a job for Mother Nature. If you must have green grass, remember it is best to water with a sprinkler, and because deep watering works best, long periods of time with the sprinkler running are necessary. Grass should be watered when it begins to be feel less springy when walked upon, when it looks distressed, or if it has a black /gray cast to it when viewed through sunglasses.
If you’re vigilant with your watering, your plants will thrive. Remember that letting water seep deeply into the soil is more effective than simply watering the top layer of soil. And proper bed prep and the use of mulch can help the soil with water retention and keep water evaporation to a minimum – a plus during the hot months when other summer activities make it harder to be ever vigilant.
Barbara Arnold is green corps coordinator at Franklin Park Conservatory.