The Tibetans celebrate the elements of the earth in colors: white for clouds, blue for sky or space, yellow for soil, red for fire, and green for water. Balancing these elements leads to harmony both in the external environment and the internal sense of well-being. I was puzzled by the choice of green for water before I visited Tibet. In our Western thinking, we use green for plants and blue for water. It wasn’t until I saw the glacial melt streams flowing briskly into rapid rivers in the high elevations of the Himalayas that it became clear. Glacial milk and rock flour are two names for the finely powdered stone churned out by a moving glacier. It gives the melt water a unique opacity and lovely celadon green hue.
In our gardens, sufficient water gives a richer, dark green hue to foliage and flowing water in small fountains or pools cools the body and soothes the soul. This has been a brutal year for the plants of St. Louis. Water is the balm for those injuries.
The difference between a green-thumbed gardener and a black-thumbed one is the ability to spot stress in a plant before it becomes extreme enough to result in permanent harm. An experienced gardener can spot a stressed plant right away. There is a tiny shift of color from vigorous green to a hint of gray indicating dryness, or too much yellow green in the undertone indicating poor nutrition. Leaves turning yellow and dropping off indicates over-watering, and a vigilant gardener will notice it with the first leaf. The black thumb gardener may take 10 or a hundred leaves—or a completely dead plant— before figuring out the problem.
The attentive gardener knows that this summer’s heat and drought has been ruthless to all of the plants in our landscape: trees, shrubs, vegetables, flowers and lawns. Most people hurry out to set the sprinkler to save the grass. This is a year to let the grass go. It can be replaced in a season or two, if at all. Wooded gardens use less water in drought, reduce storm-water runoff in rain, take no fossil fuels to mow, provide shelter for wildlife, shade for humans and lower energy bills. If this summer’s extreme heat is a sign of things to come, we will need to re-think our entire gardening strategy.
Some plants are always fragile in the heat of our St. Louis summers, but we grow them knowing they will look a little rough in August. Japanese maples and tri-color beech are two of the worst for summer sunburns. Julie reports heat scorch (burned leaves) this year even on tough plants like the stalwart, ubiquitous yew. Anyone who drives through the city can see trees and shrubs that have lost the battle with the elements, some flashing brown and collapsing in the course of a single day.
Julie was once asked by one of the Missouri Botanical Garden plumbers why we over-watered the turf so much. She explained to him, “We’re not watering the lawn, we’re watering the trees.” Trees need deep watering. It’s better to water really well once or twice a week than it is to spritz the surface daily. Deep watering will encourage a stronger, healthier, more extensive root system that is able to take up water more efficiently. Light surface waterings that do not penetrate far can actually draw the healthy root zone up closer to the surface and set the plant up for failure when light watering is stopped— like during a vacation. The balance is delicate. A standard rule of thumb is an inch per week delivered in one watering session.
In case the weather doesn’t improve, here are some tips on watering wisely:
- TAKE CARE OF YOUR TREES FIRST. You can lose a tree quickly in this heat if it doesn’t get enough water. A large tree may use 40,000 gallons of water in a year, most of it on hot summer days. Your target area is the whole root zone of the tree—from the trunk out to the edge of the drip line.
- LET THE LAWN GO. You can replace a lawn in a season. It takes a lifetime to replace a tree. Become more observant about spotting water stress in all of your plants. Look for hints of droop, curling of leaves or the slightest graying of foliage and water immediately if you spot these signs. Hand watering, while time consuming, is still the best way to stay in touch with your garden.
- BECOME MORE SCIENTIFIC. Use a rain gauge. Measure how much water you’re actually putting down by placing an empty cake pan or tuna can under the sprinkler and run the water until it holds an inch of water. In-ground irrigation systems also need to be calibrated. Most are set for turf, which will not deliver enough water for the trees.
- BECOME MORE EFFICIENT. Soaker hoses lose less water to evaporation. Mulch beds well to retain moisture more effectively.
- BE AWARE OF LOCAL CONDITIONS. It scares me to hear of wells running dry in Wildwood. We have avoided watering restrictions so far, but it looks like you could walk across the Meramec River south of the I-44 bridge.
- USE THE RIGHT TOOLS. A long-handled watering wand lets you put the water exactly where you want it without a lot of waste.
Some people water nothing, saying they don’t want a high water bill. An extra $50 or $100 on the water bill is peanuts in comparison to the cost of taking down a mature tree. Removing a large tree can run well into the thousands, not to mention the higher bills for air conditioning due to loss of shade and the replanting costs for new trees. And even after this bad stretch of weather has broken, keep watering your trees well into October. It’s always good to send them in to the winter well watered— especially evergreens—so they don’t get desiccated from drying winter winds.
Patricia Raven, Ph.D., has a doctorate in ornamental horticulture and Julie Hess is senior horticulturist at the Missouri Botanical Garden.