Gardening at Altitude

Tips for the San Juan Grower
By Mary Duffy

Let’s face it. Gardening in Telluride isn’t like gardening in Eden. It’s tough to propagate anything but hardy natives at 8,750 feet and higher. The growing season is short, the soil rocky and the climate harsh. But if a bounty of flowers can sprout year after year from a craggy slope above treeline—with only three months to flourish, no artificial fertilizers to nourish, little soil and no protection from the elements, grazers or pests—imagine what you can grow with a little patience, a handful of seeds and some thoughtfully prepared soil.

Most Telluride gardens are between 8,000 and 10,000 feet in elevation, an environment generally referred to as the montane life zone. The U.S. Department of Agriculture places Telluride in growing zone 3, based primarily on minimum winter temperatures. Many plant and seed catalogues or nursery tags use this designation to indicate a plant’s cold hardiness, but the zone designation doesn’t take into account a plant’s tolerance of aridity, thin air, intense sunlight and poor soil.

The San Juan Mountains are considered semi-arid, despite receiving between 20 to 24 inches of rain annually. A lot of this precipitation comes in the form of snow, and much is lost to evaporation. The climate is also low in humidity, which means the air doesn’t hold heat well. When the sun sets, the temperature drops dramatically. This gives way to chilly nights, which can be tough on nonnative species. Because of the altitude, there are only 60 to 80 frost-free growing days per year. Annually, the average air temperature is 38 degrees Fahrenheit, with winter lows dipping into the negative 20s and an occasional summer high in the 90s. The sun is intense, and it shines 300 days per year. Winds off the arid western deserts also contribute to the dry climate.

It sounds daunting, but in actuality, it’s the microclimates that give cultivating an edge. Finding the best location for a garden, whether it’s in a sheltered depression, lee of a house or on an east-facing slope, can make all the difference in its productivity.

The San Juan Mountains are an extension of the Rocky Mountains, and they aren’t called the Rockies for nothing. Native soils tend to be thin, loaded with stones and slightly alkaline (the pH level is elevated as opposed to acidic soil, which has a low pH). The soil substrate is also rocky, often with a good amount of silt or a conglomerate of rock and clay. Even though forest and river corridors support an abundance of plant life, these soils won’t sustain nonnative ornamentals. But with effort, soils can be built.

The first chore is to dig up, loosen and remove some of the rocks from the plot. Then pick up a handful of soil and roll it in your hand. If it falls through your fingers, it’s too sandy. If it’s sticky and gooey, it contains too much clay. Neither is desirable, because sandy soils don’t hold moisture or retain enough nutrients, and clay soils don’t permeate well and are too dense for roots to penetrate. Both can be remedied with the addition of decayed organic matter, preferably compost.

For a healthy start, a garden needs a minimum of four to six inches of good topsoil with well-rotted manure or compost mixed in. If you’re not immediately planting, cover the exposed soil to avoid giving dandelions and invasive weeds a head start. A top layer of mulch—wood chips, shrub clippings, weed-free straw, jute erosion-control blankets (no plastic), or medium-size rocks—will inhibit weed growth and retain soil moisture.

Not sure of what your soil is lacking? Gardeners can obtain a free scientific soil test through the Colorado State University Cooperative Extension office (970.327.4393) in Norwood by stopping at 1120 Summit Street for a soil bag and the requisite paperwork.

Even though we’re at the top of the San Miguel watershed, water shortages do occur in the region. Native plants and their hybrids only need supplemental water until they are firmly established. Depending upon rainfall, this could mean watering every other day the first season, less the next year, and none from the third year on, unless it’s an especially dry summer. Ornamental plants, flowering exotics and vegetable gardens require more water. Frugal drip irrigation systems work well for flower and shrub beds and containers, and smaller gardens can be adequately watered with a soaker hose and watering can. For those who are gone frequently, or don’t enjoy communing with plants on a daily basis, automated irrigation systems can do the job. All watering should be done early or late in the day to avoid moisture loss from evaporation.

Pests and Grazers
Although this altitude isn’t as hospitable to the multitude of insects found in the lowlands, we have grasshoppers, aphids, flea beetles, webworms, boring larvae and, under the cover of darkness, nibblers. Compared to gardens in more humid environments, our losses to insects are barely noteworthy. Only take action when the problem is serious enough to damage the plant. If you must mitigate insect assaults, do so with environmentally safe products. Because runoff from your garden is part of the San Miguel watershed, it’s in all of our best interests to use only organic fertilizers and pesticides. The Web is full of beneficial tips and home recipes for insect management.

Deer and elk will visit your garden, especially in neighborhoods that are free of dogs and fences, but—once again—native species will better tolerate their foraging. The opportunity to watch a deer trim your rose bushes or a bear harvest your crab apples isn’t one too many people cherish, but remember: Where your garden now resides may have been a deer’s favorite gooseberry bush or a field of fine fescue that your homebuilding laid to waste. Plant extra and give a little. Native plants have evolved to tolerate grazing and will survive better than exotics.

Sustainable Gardens
In the 1990s, xeriscape gardens were trendy. The object was to plant a garden that needed little water or maintenance. On southeast-facing slopes and open wind-exposed mesas, xeriscaping is still a good option, and many seed companies offer xeriscape seeds. Master gardeners have found that although this practice may be necessary for places such as Phoenix and Las Vegas, the mountains, mesas and river valleys of the West fair better with an emphasis on native species and their commercially produced hybrids.

Rock gardens are a San Juan natural, not only because of the plethora of rocks, but because stones inhibit evaporation of moisture by wind and sun, provide protection, and store the sun’s heat on those chilly summer nights. To plant a rock garden, first remove most of the stones from the plot and prepare the soil by loosening the substrate and adding compost, fertilizer and mulch. Replace the rocks in a manner aesthetically pleasing to you and plant around the hardy lodes.

A Bakers Dozen of Altitude-Suited Perennials and Native Hybrids
yarrow (Achillea)
columbine (Aquilegia)
snow in summer (Cerastium)
sweet woodruff (Gallium)
hops (Humulus)
iris (Iris)
blanketflower (Gaillardia)
flax (Linnum)
lupine (Lupine)
forget me not (Myosotis)
poppy (Papaver)
penstemon (Penstemon)
stonecrop (Sedum)

Flower Pots
Container gardening is a regional favorite for good reason. With proper soil preparation, planter placement and watering, these gardens are easy to maintain, fast growing and colorful. Even a condo with only a deck can be home to a flower, herb and/or vegetable garden. Container gardens are also easier to protect from wildlife and Mother Nature—stealth chipmunks and squirrels being the exceptions. When an early freeze is in the forecast, you can move the containers inside temporarily.

Picking a pot can be as difficult as choosing what to plant in it. Cheap plastic planters deteriorate when exposed to UV sunlight, especially at high altitude. Terra-cotta pots dry out rapidly, making glazed ceramic pots with drainage holes a better choice. Wood also suffers at altitude and can rot. Natural redwood and cedar are the most resilient—sans creosote, penta or other toxic compounds that can damage plants. In lieu of synthetic fertilizers, such as Miracle-Gro-type concoctions, try a homemade tea of manure, liquid fish or seaweed emulsion. Frequent watering washes away nutrients, so it’s important to fertilize regularly.

Top Ten Annuals Suitable for Containers

Vegetable & Herb Gardens
A vegetable or herb garden can serve two purposes: beauty and sustenance. Red kale, flowering nasturtium or a colorful mix of oriental greens are both pretty and edible. Look for flowering varieties that are good “companion” plants—those that fix nitrogen in the soil or ward off certain insects.

Top Ten Food Crops at Altitude
leafy greens

The Bottom Line
A garden is something to be enjoyed. If you’re constantly battling to keep your garden healthy and fruitful, call a local landscaper or join the community garden for green-thumb advice and hands-on experience. Or as master gardener Bob Perry suggests: “Walk away from your landscape for two months and see what survives. What survives is sustainable, what doesn’t is on life support and should be replaced with more resource-efficient landscaping.”