Drought, Water Restrictions and Gardening: How Can They Go Together?
I think we were all caught off guard by this drought, by how fast we were forced to see dying trees and brown lawns and by the difficult discipline of watering restrictions. This was especially true in Boulder and Lafayette where mandatory restrictions began in May. Actually, 2002 is the third year in a genuine drought, which some of us without city water supplies can confirm. This year all around Boulder, Red Twig Dogwoods turned brown, linden leaves were scorched, Norway Maples suffered, many viburnums were looking very stressed, and trees in medians defoliated or died. Gardeners caught in the crunch between weeks of hot, dry weather and few opportunities to water, held off most of their planting projects; some started talking about moving away to where they could garden. For Denver and other Colorado cities, next year could be much worse.
Now begins the new education about growing plants while conserving water. We have some experience with xeriscape and its seven principles, but they are no longer enough; we have to go to the next level. We are going to have to be much more careful in our plant selection, and in grouping plants of similar water needs. We are going to have to give closer attention to microclimates: distinguishing the areas that bake from the areas that get some shade, recognizing south from east, noting the protective presence of a boulder, a tree, a shed, a downspout; and mapping the movement of the sun and the reach of the wind. We are going to have to learn how to use our water most effectively. We are going to have to learn more about mulching, about anti-transpirants, and about products and amendments that hold water longer. We may even have to adjust our idea of beauty to include dormant, brown lawns; more modest displays of flowers in the summer months and even dry and drooping foliage, stress and death. We will go through a transitional period which will be frustrating and painful, but then we will figure it out and our gardens will be better adapted. Even if we get our needed snow pack this winter, water conservation will remain a vital concern.
First things first: SAVE THE TREES. Trees in general are not very drought tolerant. We didn’t have urban forests in Colorado until humans started planting them and watering them. Yes, of course, we have cottonwoods and willows along streams and some boxelders too, but most of our trees, especially shade trees, are imported. On top of that, most irrigation systems are designed for turf and assume that if trees are growing in the lawn, they will be watered. In the first place, most turf is watered too shallowly (and Boulder’s 15 minute twice a week restrictions further encourage that problem); and secondly, when lawn watering is prohibited or limited, there is no system in place to water trees except by hand, which then takes too much time to comply with restrictions. Thirdly, trees in cities often have confined root systems, and are often overplanted with grass, perennials and other trees which compete for the water.
These problems became apparent in Boulder this year as trees in small median and parking lot plantings were the first to show stress. The newly planted trees with small and reduced root systems (as with ball-and-burlap trees), and the old and stressed were the main trees to die or defoliate. How the remaining trees are cared for in the coming year or two will be a matter of life and death; they are stressed and more vulnerable to pests and diseases.
Trees do take a lot of our water, but they save water too. This summer some of the only green lawns in Boulder were under trees. If global warming is happening, we will need at least some trees to save us from the heat, to keep the gasoline in our cars from out gassing in the parking lots, and to create moderated environments in which other plants can live. At this time, I will not go into the many values that trees add to our quality of life, but let’s not let our trees die while we’re trying to figure out how to save water. Remember the trees now casting our shade are twenty to a hundred years old; it will take that long to replace them.
Some trees that require little water are: Hackberry, Golden Rain Tree, Ponderosa and Pinon pines; Bur and Gamble Oak; Russian, Toba and Washington hawthorns. Trees with somewhat low water needs are: Silver maple, Green Ash, Honeylocust and Catalpa.
This drought has brought up some new and challenging questions:
- Do trees take more water than they save? Which ones?
- Is bluegrass a xeriscape groundcover if we can let it go dormant in the summer?
- If my plants are dying under the current restrictions of 15 minutes twice a week, can I water once a week for 30 minutes to save them by watering more deeply?
- If I buy a water efficient toilet which will save 10,000 gallons in a year, why can’t I have at least 5,000 gallons more that I could use for my gardens?
- How can I recycle or reuse my water?
It is easier to come up with questions than solutions. To be fair to the municipalities, they were caught off guard as much as we gardeners, and it will be some years before they/we figure out how best to distribute our water. Even though my low-producing well has put me on water restrictions for the past 17 years, and all my gardens are by necessity xeriscapes, I wanted to get a broader perspective on this drought, so I asked some good local gardeners how they experienced this year’s water crisis.
I interviewed Lauren Springer, Marcia Tatroe, Bob Nold, Jim Knopf and John Spaulding:
“Did you lose plants to the drought this year?” Marcia lost dozens of plants, most of which were newly planted. Lauren lost both new and established, noting as did John and Bob that the losses were due to the cumulative effect of 2 or 3 dry seasons. Jim lost a few things.
“Were the losses due to the heat or mainly to the lack of water?” Lauren and Marcia thought both heat and drought, though Lauren said mostly lack of water. John said more likely heat because he was watering adequately. And Bob said his died because he was not paying attention to them. He also mentioned that his losses of alpine plants were very low, because they can continue to grow under a wide range of hot and cold temperatures.
In a recent talk, Kelly Grummons mentioned that in general, the metabolism of a perennial slows down above 80 degrees F and nearly stops at very high temperatures. A Boulder city forester told me that the burning leaves of the Norway Maples was due to their heat sensitivity, and it seemed that vegetable gardens that were planted early thrived and those planted late in the heat grew little until temperatures cooled.
“Name plants that did well this year with limited water supply.” Jim: Zauschneria, Buffalo Grass, Hesperaloe, Melons, Blue Mist Spirea, Junipers, Apache Plume; John: roses, and annuals did better under water restrictions where maintenance companies had been over watering
Lauren: Fernbush, Saltbrush, Rabbitbrush, Artemesia versicolor, Wright’s Sacaton, Salvia pachysilla, Apache Plume; Bob said all of his rock garden plants did well; Marcia: Desert Four O’Clock, Russian Sage, Apache Plume, Mt. Mahogany, Leadplant, Desert Mahonia.
“Name plants that died or did poorly.” Lauren: Veronica teucrium, all tall penstemons, carex; Jim: Red Maples, Sugar Maples, Norway Maples, Birches, High Bush Cranberry, Red Twig Dogwood; Marcia: Potentilla atrosanguinea, Ligularia, Eryngium alpinum, Microbiota decussata.
“Do you use a mulch? What do you recommend?” John suggests 2″ of coarse mulch applied only after the soil has been thoroughly watered. He says mulch that is too fine or too thick (4—8″) will not permit water to get through. Bob uses straw or anything organic, but prefers rock as the best possible mulch, allowing water to penetrate and then holding the water for a long time. Marcia uses mulch extensively, preferring pine needles loose or shredded, and chipper chips if they are re-shredded.
John Starnes says he has good results with a 6″ deep wood chip mulch.
“What were your water restrictions and how did they affect your garden?” Lauren’s well went dry May 7 and she had only 7″ of rainfall up to September, so she mostly watered trees, roses and woody plants. Marcia could water every third day as long as she wanted until Sept. and then one hour every third day. She only applied a half inch a week and that was enough. Her dry garden was only watered 3 or 4 times all season. She would prefer a water budget, watering when and how is best for her garden. Bob said his restrictions had no impact since he is used to having no rain and watering everything by hand. Jim noted that his water use went up with the restrictions. He did not like the shallow watering which resulted from Boulder’s 15 minutes twice a week rule. He would prefer more flexibility, measuring use by the water meter.
“Share an insight from your experience of this year’s drought.” Marcia: Most of my trees are small native trees and they did fine, but I recommend putting off tree planting until we see what next years’ water supply looks like. If you do plant one, choose one under one and a half inch caliper with a large rootball, mulch it 6″ deep beyond the width of the rootball, and water it once or twice a month over the winter, and be prepared to carry gray water to it next year.
John: When lawns are installed without proper tilling depth (8—12″) and without compost amendment, they will not be just dormant after a drought, they will be patchy at best or dead in two seasons of restrictions. It is best to start lawns of all types from seed so as not to get a horizontal barrier to water and nutrient movement. Even bluegrass, if done right, can be very disease, insect and drought resistant.
Bob: My bluegrass and turf-type tall fescue were both watered 15-20 minutes every ten days, and both look green and healthy. People should not be allowed to plant trees under water restrictions. Existing water supplies can’t possibly support more trees than we already have. Proper planting in the right place saves water.
Jim: Bluegrass won’t live on two tenths of an inch of water twice a week; patches of grass and bare ground is not a lawn; a half an inch of water once a week is much better. If we had a water budget system, that would allow more opportunities and use no more water. We could then design landscapes that fit the budget.
Lauren: Take care of the trees; this is our most important group of plants. We are lucky to have gardens, and here in Colorado you have to love gardening to put up with the duress, and to struggle with the obstacles. Colorado gardeners have to be tough and optimistic.
We may be going through a painful period, restricting our plant palette, and our freedom to water as we please, but this discipline is probably good, because the earth is not growing with the human population, and we must prepare for conservation of not just water, but of all our natural resources. A friend in Italy has a sign in her kitchen: “When you use THE WATER, give thanks. Can you imagine the world without her.” And another friend, a physicist at the Solar Energy Research Institute, believes a time will come when each person will get an energy allocation as well as a water allocation; and that we will have to make some hard choices between heating the house and miles of driving, for example. Mr. Bush may believe that we can keep coming up with cheap oil and keep sending ever more carbon dioxide into the atmosphere, but I’ll bet a lot of people are beginning to get the picture. As Chief Seattle put it: “The earth does not belong to us, we belong to the earth.” Statistically, average droughts are five years long. If that is true for this drought, we get two more years to figure things out and make adjustments with the pressure of this natural discipline. However droughts can be 10–15 years long, and besides, more houses are being built and so more demand will be placed on the same amount of water.
This may sound grim, but there are plants that are surviving this drought with even less water than restrictions allow: native plants, for example. And my xeriscape got only five waterings this year and still looks all right. And if I make some improvements, it will look even better. We can all share our successes and failures with each other and our gardens will get better adapted to drier conditions. Natural Selection is a ruthless and accurate designer. If, for example, all your Sunset Hyssop (Agastache rupestris) died from drought except one, and it flourished, it may have found the perfect spot, OR if it was seed propagated, it could have a slight genetic deviation that makes it more drought tolerant. So save your seeds from your best drought survivors and share them with your friends and neighbors. A drought cycle is the best time to cull the pretend xeric plants from the truly xeric plants, as well as to discover more drought tolerant strains. If we pool our seeds and cuttings, share our discoveries and insights, and follow these with real changes in our habit patterns and in our gardening, this drought could be a great education for better use of our precious resource: THE WATER.
In future issues of Colorado Gardener, we will go into greater depth on the drought situation and into practical approaches to gardening under drought conditions.
Copyright 2003 by Mikl Brawner