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by High Country Gardens

Chilopsis and Muhlenbergia
Chilopsis with Muhlenbergia

Fall is the time when gardeners prepare their gardens for winter, whether it's cold temperatures, heavy snows, drying winds, or depredation by grazing animals. Gardeners living in colder areas will need to start winterizing the garden in September and October while warmer climate gardeners may wait until November and December.

Fall Cleanup

After a hard freeze perennials will typically drop their leaves. These leaves should be cleaned up if you have insect problems. Many problem insects will over-winter in the garden in the form of eggs or larvae. Leaves from overhead trees should be raked as they can smother garden plants when allowed to accumulate in great depth.

In an effort to clean up your garden, don't be in a hurry to cut off the stems and leaves of perennial flowers and summer-blooming shrubs (i.e. Butterfuly Bush, Blue Mist Spirea, Russian Sage.). Wait until mid-spring. Many plants more successfully over-winter when the stems are left on them until spring. The stems provide energy reserves for the root system and will also catch blowing snow that helps insulate the plants and provide extra moisture during winter months.


Mulching is used to:

  • Enhance appearance
  • Control weeds
  • Conserve moisture in the soil
  • Maintain warmer soil temperatures longer in the fall (to allow for increased root growth)
  • Reduce frost heaves
  • Delay early spring growth that could be damaged by late spring freezes

Many types of mulch are available including composted organic matter, gravel and straw. Mulch should be applied to a depth of 2 inches and slightly deeper for trees and shrubs. With newly planted perennials mulch should not be applied all the way up to the neck of the plant. Once the soil has frozen, it is important to not add mulch. You will want to keep the ground frozen until spring so plants are not heaved out of the ground by alternate freeze and thaw cycles.


Plants will have a much better chance of surviving the winter if they receive adequate water (deep soakings) during the fall months up until the time that the soil freezes. If the soil is not frozen during winter months, and snow or rainfall is minimal, plants should be watered every 3-4 weeks, weather permitting.


Fall is the time to apply a winterizing fertilizer that promotes root development but does not promote lush, new top growth. For perennial flowers, spring blooming bulbs, shrubs and trees, we use Yum Yum Mix Winterizer.

Applied generously, at recommended rates, the plants will be ready to grow with the arrival of spring. For newly planted perennials we use a combination of Superthrive and Saltwater Farms Sea Com-PGR liquid seaweed to help the plants to help avoid transplant shock and encourage the development of a strong root system. You can also supplement the Yum Yum Mix Winterizer with a topdressing of Planters II, an organic trace mineral fertilizer.

Fall is the best time to fertilize native and turf type grasses. Buffalo and Blue Grama grass will benefit from a single application of high nitrogen Gro-Power 5-3-1 in October or November (earlier in the north, later in the southern parts of the West). A 20 lb bag of Gro-Power will fertilize a 1000sq ft patch of native grass. Fescue turf needs two applications of Gro-Power; one each month as above. A 20 lb bag of Gro-Power will fertilize a 500 sq ft section of Fescue turf one time.


Most pruning is best done in late winter or early spring. An exception is pruning branches that may be subject to damage from strong winds or heavy snow. Climbing roses with very long canes may be trimmed back so they don't whip in the wind. Tree branches that have narrow branch angles that may be prone to breakage in heavy snows can be pruned in fall.

Animal Depredation

Spray Deer-Off repellent on the twigs (and foliage, if the plant is evergreen) to discourage browsing deer. Fall is an active time for gophers. Watch for fresh soil mounds to determine if they are out eating roots in your landscape. Mole and Gopher Repel is an excellent repellant that is sprayed onto the top of the soil and watered in.

Young shrubs and trees should have their lower stems protected from feeding rabbits if they are a problem in your neighborhood. This is especially true in snowy areas. Rabbits will burrow under the snow and nibble on the bark. Brown paper tree wrap is excellent to protect trees. Multi-stemmed shrubs and trees can be protected with chicken wire cylinders or other mesh-type barriers placed around the base of the plant.

Correcting Iron Deficiencies

If plants in your landscape have very yellow (chlorotic) foliage they may be suffering from an iron deficiency. Fall is the best time to increase the amount of available iron with a topdressing of Greensand and flaked soil sulfur. Greensand is a rich source of iron and potassium. The soil sulfur lowers the soil's alkalinity to make iron more readily available.

For chronically iron-deficient plants, dig a ring of one foot deep holes around the drip line of the tree and add a mixture of the Greensand, soil sulfur, along with generous amounts of compost into the holes.

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