Critical Aspects of Soil Composition
for Planting and Growing
Garden Tip
Technical Bulletin Series
Gardening Tips for successful and beautiful Landscapes and Gardens

Being successful when installing new plants into your landscape actually involves several important considerations. In this Garden Tip the concept is Soil Amendments. Even if you have really good soil that doesn't drain too fast and yet doesn't drain slowly, extra organic matter (that comes from compost or organic planting mix) provides the food for soil bacteria to establish and grow. Living soil is one of the "keys" to success in the garden.

In most circumstances anywhere in desert type climates high levels of clay (sometimes sand) and very low levels of soil microbes are encountered. There are many varieties of clayey soil types (see soil triangle), but one thing most all have in common is poor drainage and mostly sterile. This is a real challenge to the development of new roots.


It will Die!

Proper planting and irrigation techniques can prevent this.

Most of the plants that fail to establish after transplant have root systems that resemble this (above). The shape of the original root ball is clear and when it is removed none of the surrounding soil is attached. This is because the roots have not grown into that soil. When the surrounding soil is improperly amended the likelihood of this development is high. Soil with poor drainage is too compact due to high clay and lacks the oxygen needed. Usually the deeper soil will be without moisture as water will not permeate properly. Most Native soil in desert climates just isn't the right stuff for success. If, before starting, you know your soil type (see Garden Soil Calculator) and mix the proper combination of amendments into it - Your chance of success goes way up!
Here we can see the form of the original root ball as it came from the nursery pot. We also see how the roots have grown into the surrounding soil. This is the condition needed for a plant to survive transplanting and begin to thrive. This is our goal!

Growing Healthy Plants

Can be a simple science

and it begins inside the soil
with what we know as Root Systems

Native Soil is the term used for the
Soil you have to start with
(good or bad)

Amended Soil is
what you have after mixing in a formula
of other Soil Media Materials

Soil Composition in Desert Climates

The "natural" process in the evolution of soil composition is for clay to rise to the top and sand (large particles) to penetrate more deeply. In regions of the Country where there is little rainfall there are few plants and not much in the aspect of root creation.

The soil becomes devoid of microbes and does not easily change state of composition. If sandy, it tends to remain sandy, and if clayey, tends to remain hard and high clay. More often than not, if you live in an arid part of the country, your soil is likely high clay. You can NOT assume this however. Soil composition testing is not rocket science, but actually knowing the type of Native soil in your landscape will improve your chances of success ten times over!
Installing New Plants
If you want your new plants to survive and ultimately thrive; you absolutely need to provide a good soil composition and adequate volume of that soil for the area where they are to be planted. If these plants are intended to grow to be large shrubs or trees, you will need to do things in the future that will help their root systems to grow large enough to support the size they will become. This is simple to understand but so often forgotten when the time comes to expand.

From my experience; Root System Volume is really a simple math equation; Canopy size (height times width), equals 120% the minimum size of the root system. As in the sketch above the plant would like a more equal ratio than 12:10 but not less than that. Drought tolerant plants can do well even though their root systems may only be 50% the size of the canopy.

Understanding the square foot area

to be irrigated

An example might be; the tree is 10 feet tall and 15 feet wide, so the square foot area for the root system should be at least 125 sq. ft. (or about 11 feet by 11 feet). The depth of the root system in dry climates will be considerably less than in climates with 20 inches or more of rain annually. This is because of the greater depth that regular gentile rainfall will penetrate soil. In dry climates a good rule is for a minimum depth of 10 inches, increasing to 18 inches where practical.

When roots are shallow - soil dries quickly and the plant easily wilts!
Hard packed, high clay soils do not provide much of an opportunity for roots to grow and spread. This is simply because the moisture will not permeate throughout the soil area. The best way to create larger healthy root systems for new plants is to dig large enough holes and then PROPERLY AMEND the soil that goes around the new root ball.

Small holes or improper amendment formulas produce root systems that look just like the pot the plant came in (see Pot Shaped Roots above).

Though occurring less often, soils with very high sand ratios can also be a problem. In these soils; water and nutrients quickly leach away from the plant roots and wilting or nutrient deficiencies are likely. In each case, soil amendments are vital to correct the problem, and the formula for these amendments is vastly different.

Soil Amendment Formulas differ Greatly - based on Native Soil Type

Compost - Planting Mix - Potting Soil - Perlite - Sand
Various combinations of these amendments, when mixed in with your native soil will make a "new soil composition" that provides the characteristics needed for success.

To skimp on Amendments and hole size invites plant stress & failure!
The Garden Calculator Pro-I (a free online tool) provides complete and accurate irrigation lay-out and scheduling for the landscape area under improvement. Including everything from identifying the soil composition to emitter-count and run times, this on-line calculator that goes with you right to the job / plant site will ask a few simple questions and provide many specific answers and recommendations. The proportions of native and the various amendments are specified for each planting analyzed.

No guesswork involved and a complex analysis is conducted instantly.

Additionally, this online calculator will provide comprehensive
specifications for the irrigation required.

Additional information found on these following pages!

Understanding the critical importance of soil composition is essential to being successful at providing better root growth conditions for the plants in your landscape. Visit TB1482 "Understanding Soil Composition" for some good basic information on the all-important category of successful gardening.