Mountain Gardening Advisories

Teller County Master Gardeners



Trees and Shrubs


When planting trees and shrubs, much thought should be given to the plant and site selected for its new home.  It is necessary to understand the soil and climatic conditions in our area.  Teller Count is semi-arid, with approximately 15 to 20 inches of moisture annually, and the soil is alkaline and generally low in organic materials.  Altitudes range from 7800 feet to 10,000 feet, which creates some unpredictable weather.  Severe temperature fluctuations, low humidity, very cool night temperatures (even during summer), drying winds year round, heavy snow accumulations, and sudden hailstorms can strain the vigor of even the hardy native plants.


Introduced species will need every advantage possible, and you may be forced to accept some compromises in their performance simply to have them survive.  For example, there are specials problems related to flowering trees and shrubs because of our short growing season.  They will blossom later than nursery catalogs indicate and whether they flower at all may depend on the severity of the preceding winter and spring.  Hardier fruit trees may survive the altitude and severe winter, but will rarely produce fruit.


Non-native trees are hard to establish but limited success with Hopa crabapple, European white birch Siberian elm, green ash, and honey locust have been observed.  If you have a specific tree or shrub you wish to try, find out everything you can about that particular plant and compare its requirements to our growing conditions and your own micro-climate before making an investment.  Special attention must be given to soil, water, and light requirements of each plant, and transplanting techniques must be carefully observed.


Colorado native trees that should be successful above 8,000 feet are:  Rocky Mountain juniper, Englemann spruce, Colorado Blue Spruce, Ponderosa pine, limber pine, lodgepole pine, bristlecone pine, white fir and Douglas fir.  Austrian, Scotch and Eastern White pines are not native and are not recommended.


Shrubs that will tolerate our climate and can be introduced with success are:  common and Persian lilac, Tartanian honeysuckle, Austrian copper rose and Harris yellow rose, Siberian peashrub red-osier dogwood, Nanking cherry and Peking cotoneaster.


Native shrubs can be transplanted fairly easily, but require the same attention as an introduced plant until established-about two years.  Keep in mind the requirements of each plant and place the following accordingly:  mountain mahogany, shrub-type potentilla, juniper, western sand cherry, three-leafed sumac and rock spirea (Holodiscus).  These shrubs are very drought tolerant.  Chokecherry, currant, gooseberry thimbleberry, willow, alder, mahonia, red-berried elder, and mountain ninebark require a moister site.


Plants should be “hardened off” prior to planting.  Do this by placing the new plant outdoors for an increasing period to time each day and protecting it from extremes in temperature at night.  If the plant has bare roots, protect the roots by placing them in a pail and covering with loose mulch.  Keep moist (but do not drown) and shelter the plant from harsh cold and overly sunny or windy conditions.   Keep in mind that barefoot plants should be planted as soon as the ground can be worked in the spring, preferably before bud break and the soft growth stage.  Balled-and-burlapped or container grown trees and shrubs can safely be planted later, but may suffer from some leaf loss if the air temperature is very warm.


The following transplanting and maintenance practices should give your plants a good start and keep them healthy for years:


1.  Dig the hole at least three to five times as wide as the root ball, and two to four inches shallower.  This allows excess water to drain away from the plant.  The bottom of the hole should be cone-shaped to accommodate a bare-root plant and undisturbed for balled-and-burlapped or container stock.  This will prevent sinking and tilting.


2.  Remove all containers or wrapping materials.


3.  Loosen the bottom few inches of the root ball land place the plant in the hole, spreading the roots slightly.   If the shrub or tree is pot-bound and the roots have begun to circle inside the container, use a sharp knife to cut up and down the ball ½ inch deep in four or five places.  If the majority of the roots are at the bottom of the ball, split the root ball all the way through from the bottom about half way to the crown of the plant.  Spread the two halves over a mound of soil in the planting hole.


4.  Mix backfill with a small amount of course organic matter such as Canadian sphagnum peat, well-aged manure or compost.  Too much organic material in the planting hole will create soil barriers that will not allow for the free passage of water.  Replace the backfill, and water slowly to allow the soil to settle.  Do not tamp the backfill, as this will compact the soil.  The final planting depth should be the same as the original planting depth in the container, or just below the natural taper of the trunk.  Fertilizer in the backfill is not recommended as it may burn tender roots.  Feed the plant in the spring of the second season after planning and once yearly thereafter.


5.  Water newly planted trees and shrubs when the soil feels dry at a depth of 4 to 6 inches.  Water deeply, to a depth of 12 to 18 inches.  Avoid frequent light watering that will promote shallow root development and create an increased susceptibility to drought stress.  Supplemental watering during the winter is necessary even for established plants.  Water only when the air temperature is above freezing and the soil is not frozen.  Water early in the day so the water will have time to soak in before freezing occurs during the night.  The majority of the feeder roots are in an area from a point halfway between the trunk and the outer tips of the branches to approximately one foot beyond the dripline of the branch extremities.  This is where the water should be applied for maximum absorption.

6.  Apply a mulch four to six inches deep to help retain moisture.  Pine needles, wood chips, leaves or loose organic material are suitable.  Do not apply the wood mulch closer than four inches to the trunk since this will provide shelter for stem-chewing voles and may contribute to the mechanical damage of the plant.  Adequate snow cover is excellent mulch. 


7.  At planting, prune only those limbs, which are dead or damaged, as the plant needs the nutrients stored in branches and leaves for healthy development.  Pruning of established plants is usually done only to repair damage.  Improve appearance or stimulate flowering and growth of deciduous trees and shrubs.  Trees and shrubs that flower in spring should be trimmed soon after bloom because they begin setting the next year’s blooms immediately.  In other words, they bloom on “old” wood.  Those that bloom in summer can be trimmed in late winter or early spring since they bloom on “new” wood each season. Plants that do not bloom should be pruned when dormant, usually in late winter.  Evergreens that produce side shoots such as spruce and fir should be pruned by cutting the tips back to the desired length in late winter or early spring when the buds are dormant.  The recommenced place for the cuts is just above the side bud or side branch.  Pines, which produce few side buds, are best pruned by snapping off a portion of the young growth, or candle, which forms in late spring or early summer.  This new growth snaps off easily and cleanly when the tie is right.  Junipers can be pruned at anytime except during sub-zero weather.  Avoid topping any tree unless absolutely necessary.


8.  Young deciduous trees (with the exception of birch and aspen) and thin-barked trees are susceptible to sunscald in winter and should be protected with a commercial crepe wrap.  Begin wrapping at ground level, overlapping the wrap by one third to cover the trunk up to the second branch.  Secure with a staple or small tack.  Trees should be wrapped from November through April for maximum protection.


9.  To prevent wind or snowdrift damage, staking may be necessary.  Guy wires or ropes run through grommets at the ends of strong, soft, wide strips of material will prevent girdling injuries to the trunk.  Do not use wire through garden hose.  Place the straps around the tree below the midpoint and attach to tall stakes.  The wires or ropes should have slight sag to allow for natural sway.


Mike Corso

Updated by V. Belding

March 05