Successful Colorado gardeners learn how to take advantage of the favorable properties of our soil and how to improve it through soil preparation.

The most important thing to add to any Colorado soil isn’t fertilizer; it’s organic materials like compost, peat and manure. Organic materials are also known as organic amendments.

To organically amend soil, add a two-inch layer of organic material over the surface of the soil and mix it into the top four to six inches. Add four cubic yards of organic amendment per 1,000 square feet of soil area.

Clay soils hold water and are naturally fertile but have a tendency to pack, which can hinder plant growth. Adding organic materials loosens tightly packed clay particles to make space for the air, which is critical to plant root growth.

Sandy soils drain freely, eliminating plant growth problems from too much water. But sometimes plants in sandy soil don’t get enough water. Organic amendments added to sandy or rocky soil act like a sponge to hold enough water for plants to grow. Organic materials also hold fertilizer nutrients, another item often lacking in sandy soils.

Before planting lawns, trees and shrubs, add organic materials to the soil. Where perennial and annual plantings like flowers and vegetables are grown, the soil can be amended every year. For the best results, amend soils with organic material and then carefully regulate the amount of water given to plants.

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For a rock garden, select a spot that is open to light but is not too hot. An east facing bank or berm is ideal. Soil generally must be amended, or mixed with organic material, to make it porous. A mix of half native topsoil and equal parts coarse sand, pea-sized gravel and compost is one common recipe used by rock gardeners.

Rock gardens look best when they are bold and large, rather than puny and trivial. The rocks should all be of the same source, but of different sizes. Avoid placing them regularly or jumbling them randomly. The placement of rocks is an art and beginning rock gardeners should look up some books on the subject, spend a little time observing out Crops in nature, and try visiting successful rock gardens to see how others have done it

A mulch of gravel or a stone a similar color to the rocks in the garden will trim a rock garden beautifully. Remember, a rock garden is not designed for immediate impact. It will look sparse in its first year so plant lots of tiny spring bulbs. You will be rewarded for years to come with this sophisticated garden art form.

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Retaining walls are constructed for purely structural needs. For example, they can be used to level, retain, or terrace a sloping area; to maintain an existing grade around a tree; or to allow a more abrupt change in grade than you can achieve with graded slopes. They can also support a level area such as a patio or driveway. Generally, the more restricted or congested the site, the greater the need for retaining walls to provide usable space for landscape purposes.

Other retaining walls are used for visual effect in the landscape, and generally have several common characteristics. They’re less significant in size but more pronounced in visual character than functional retaining walls. They complement other landscape elements such as plants, paving and mulches. They’re more compatible with human activity and can be adapted to many uses, such as a bench wall, as a base for a fence, or an accent element in the landscape. The materials used to build decorative retaining walls — native stone, timbers and colored concrete bricks and blocks — are chosen to provide the desired visual effect in the landscape.

The higher the retained slope, the more structural stability is required. Many times, critical structural requirements necessitate engineering a design that considers the length of slope, site-soil characteristics, the wall material used, construction space available and height of the wall. Complex structural walls require the design expertise of an experienced engineer.