Written by: Penelope Hyland, Colorado Master Gardener

The temperatures are still cold and below freezing at night, but spring will be upon us before we know it and now is the time to start preparations.  We have been dealing with high temperatures during the summer along with drought conditions, so we are naturally concerned about the health of all the plants we are considering to put in this season along with the care of existing plants.

For all of our plants, perennials and annuals; trees and shrubs; edibles and ornamentals one of the most important elements for healthy and thriving plants is the soil that that live and take life in.

Soil is a porous medium consisting of minerals, water, gases, organic matter and microorganisms derived from the combined effects of climate and biotic activities.  It is one of the most important elements of ecosystems – both biotic and abiotic.  What is referred to as “good” soil has lots of space between aggregates and evidence of biological activity.  Soil structure refers to the size and shape of aggregates which influences water and nutrient flow.  The type of soil structure present in any location will determine crop productivity.  Lots of space between aggregates of soil allows for the flow of water and oxygen necessary for plant development.  It also allows for nutrients to flow and be available for uptake by plant roots.   The type of soil structure also allows for resistance to erosion or compaction – both of which affect the growth of plants.

Ideally, soil should include:

• 45% minerals
• 2-50% water (usually about 25%)
• 2-50% gas/air (usually about 25%)
• 1-5% organic matter (5% is ideal)
• Less than 1% microorganisms – these decompose raw organic matter – soil without microbes is considered to be dead soil

As plants grow, thrive and mature throughout the season they will deplete the soil of nutrients and so the soil needs to be amended.  Depending upon environmental conditions, the soil might need to be amended more often or with more variety of organic matter.  All soil types need to be amended at least once a year.  Dark, crumbly soil full of evidence of life is the best type of soil but even it needs to be amended annually.  There are many types of organic matter that can be found at home or others that can be purchased.  These can include:

• Compost (made or purchased)
• Coffee grounds
• Banana peels
• Egg shells (rinsed and smashed into smaller pieces)
• Shredded leaves
• Grass clippings
• Wood ash (small amounts only)
• Sawdust
• Cover crops for larger areas
• Crop residue
• Mulch
• Peat moss
• Cotton burr/seed
• Manure – needs to be seasoned first
• Perlite
• Vermiculite
• Potting mix
• Gypsum
• Greensand (for clay soils)
• Blood meal
• Vermicompost
• Wood chips

As you can see, there is quite a variety of items that can be used to amend soil.  A mixture of a few of these is best, depending on soil type and needs on types of plants and environmental demands.  The best times to amend your soil is either in the fall or early spring to prepare the soil for planting.  Amending can also be done throughout the season as you cultivate and care for the plants.  Whenever you might see any possible plant disease is also a time for diagnosis and amending as needed.

When starting new beds for either vegetables, flowers and other ornamentals including raised beds, it is best to create your own soil.  For raised beds and pots:

• Fill the bottom third with dried crumpled leaves
• Then mix in approximately 50% of raised bed soil (for raised beds), potting soil (for pots), 20% peat moss and 10% vermiculite and 20% compost

As soil compresses and levels lower, you can add anything  you have on hand to fill it out.  Every year, the soil needs to be stirred up and amended.  Mulching the plants with grass clippings, straw, dried leaves or wood chip mulch helps to keep the weeds out and the soil moist.  The mulch will gradually decompose and add organic matter to the soil.

Leaf mold is an excellent way of adding valuable nutrients to the soil.  Leaf mold is nothing but aged leaf mulch.  It helps the molding process to fill a black plastic bag full of dry leaves and just leave it over the winter outside.  As the sun warms the dark plastic, condensation forms and warms to assist the leaves to turn into mold.  This is an excellent amendment to turn into ground soil when creating new planting spaces or adding to existing spaces.

Another good use of leaves is to allow them to accumulate around the base of plants in the fall to protect the roots during the winter.  In the spring, simply crumple them up and turn them into the soil surrounding the plants they have been protecting all winter.

As you continue to amend your soil, your plants will not only survive but thrive growing fuller and healthier.  Lush, healthy plants will naturally resist weeds and pests.  Amending soil also improves:

• Soil aeration
• Water drainage
• Root growth
• Biological activity
• Texture of soils high in clay or sand

In addition, you will find that you will need to irrigate and fertilize less.  While the percentage of organic matter in the soil is relatively low, consider that over a billion microorganisms can exist in only 1 teaspoon of compost or soil.  These microorganisms are the life of the soil and of all you plant.  So, before you plant, amend your soil!