by Regina Cutter Edwards
Soil is the foundation of any garden and is very important to having a successful butterfly garden. People often plant gardens without a thought as to whether the soil can sustain the life that is being put there. Soil is important because it supports plants while supplying it with nutrients and water. If the soil is not adequate, the plant will not flourish to its fullest potential.
What is Soil?
Soil is the medium in which plants grow. It consists of broken down rocks and minerals. It also contains organic material; such as decaying plant and animal matter and micro-organisms that live in the soil. Soil also contains water and air.
Soils have three particle sizes; sand, silt, and clay. These particle sizes affect productivity of the soil. For example, sand is the largest particle size. It has great drainage but does not hold nutrients in the soil. Clay has the smallest particles and will hold nutrients but the drainage is poor. A combination of any of these is called a loam. A good garden mixture may contain 10-20% of sand, silt, and clay in equal amounts and the rest is organic material.
The best way to modify soil texture is to add compost or humus to your soil and till 12-18 inches deep for the best root development. This helps the tilth, the workability of the soil, while adding organic matter to your soil. Adding compost to clay soils will create space for air and water while providing more room for root growth. Adding compost to sandy soil will increase the ability for it to maintain water moisture and nutrients. Adding compost to any garden will increase the biological activity within the soil, retain moisture, and assist in maintaining nutrients essential for plant growth.
The three primary macro-nutrients are nitrogen (N), phosphorus (P) and potassium (K). Large amounts of these nutrients in the soil are used for growth and to maintain the plant’s health. If there is a nitrogen deficiency, plants may have older leaves or stems that are pale in color or yellow. The growth may also be very slow and limited. Plants that have a phosphorous deficiency may have small leaves that appear reddish-purple. Older leaves may appear blackened or burnt. If there is a potassium deficiency the older leaves may appear wilted or scorched along the leaf margins.
The pH in soil is a measurement of the acidity or alkalinity in soil. The pH scale is between 1.0 and 14.0. A neutral pH is considered 7.0, an acidic pH is < 7.0 and an alkaline pH is >7.0.
The reason pH is important is because it effects organism activity in the soil, the solubility of nutrients, and the availability of nutrients that are absorbed by the plant. Most plants prefer a pH between 6.0 and 7.0 because that is when most nutrients are available, although some plants require the pH to be more acidic or alkaline.
Modifying the pH in soil is only temporary and should be checked seasonally. To increase the pH, add lime. It is more difficult to lower the pH, although a mixture of sulfur, peat, and fertilizer would be a good option. At times it may be easier to just add the nutrients needed by the plants instead of trying to lower the pH. If the plants are already set, be careful not to shock them, adding small amounts instead of the whole recommended amount would be less stressful for the plants.
Soil testing can determine the types of nutrients that are in the soil and the pH level. This can be done with home tests or contact your local Cooperative Extension Service for information regarding testing services. The results will determine what needs to be added to the soil.
It is best to get your soil tested in the spring or the fall. Repeating the test seasonally is a good idea because many nutrients leach out of the ground over time and are used up by plants as they grow. If you are preparing a garden location, testing the soil before actually planting is ideal.
Gardening at Home
When you know the special needs of your soil, proper amounts of organic material and fertilizers may be added to create the perfect foundation for a butterfly garden. If possible, composting at home and the use of organic fertilizers is always beneficial for the environment as well as our gardens at home.