Garden Soil vs. Potting Soil
Garden soil vs potting soil...which should you choose? The answer depends on the ultimate use for the soil itself. Each has pros and cons, and the choice of soil depends on what you are growing and where you will use it. While garden soil is free, it has many drawbacks, especially if you are using it for seed starting or transplanting house plants. Potting soil, on the other hand, can get expensive, especially if you purchase different bagged soils for various uses. But understanding garden soil vs potting soil and when to use each type of soil is an important aspect of gardening.
What Is Soil?
Soil is actually composed of several materials. About 50% of what we call soil is solid material, and the remainder is actually open spaces between the particles, which allows air and moisture to penetrate into the soil to reach the roots of plants. The solid portion of soil contains tiny particles of various minerals and organic materials. The minerals come from rocks, which are weathered and broken down by the action of wind and rain over many years, and the organic material comes from decaying plants and animals. The open space contains about equal parts air and moisture.
Soil is measured using several factors. Garden soils are tested for pH. The pH scale ranges fro 0 to 14 and measures the acidity (closer to 0) or alkalinity (closer to 14) of the soil. An average range that many typical garden plants prefer is between 4.5 and 6 or so; some plants have specific acidity or alkalinity requirements. Soils can be tested by taking a sample to your local garden center, nursery or Cooperative Extension office. For a small fee, the soil composition, pH and other factors will be analyzed, and recommendations given to you based on what you intend to plant in the area for amendments and other materials to be added to create ideal growing conditions. The investment in a professional soil analysis is well worth the few dollars you will spend as the professional recommendations will save you time, money and effort later on, and if recommendations are followed, improve your chances of garden success.
Garden soils are generally classified as sand, loam or clay. Sand has the largest particle sizes and allows water to drain quickly. It also tends to lose nutrients quickly, too. Loam is the ideal, somewhere in the middle, with both good drainage and good fertility. Clay soils tend to retain water and lead to wet spots and compaction. Soils can be improved through the addition of natural amendments such as well-aged manures and composts.
Types of Potting Soil
Not all potting soils are created equal. The basic purpose of potting soil is to provide plants with support, nutrients, moisture and air for growth and development. Potting soil generally contains a mixture of pine bark, peat moss, and either perlite or vermiculite. Pine bark is a by-product of the lumber industry and adds organic material and moisture to the mix. Peat moss is a naturally occurring moss that soaks up both water and air and releases them slowly; it can hold up to 20 times its weight in water. Perlite added to soil mixtures enhances drainage, while vermiculite, a naturally occurring mineral, helps retain moisture and nutrients. It is very useful in house plant potting soil mixes.
Whenever you purchase bags of potting soil, be sure to purchase soils marked "sterile." One of the drawbacks of using garden soil indoors is the chance for bacteria and fungi to grow and harm your house plants or seedlings. Another drawback is the potential presence of insect eggs or hibernating insects in garden soil. If such soil is brought into the warm indoor temperatures of the average house, the insects can hatch or awaken, causing an unpleasant infestation. Sterile potting soil has been heat-treated to kill all types of unwanted pests.
There are several types of potting soil:
- Seed starting mix - these are generally lighter and fluffier than other soils, allowing tiny seeds an easy pathway to put down roots.
- General house plant soil - may or may not be mixed with fertilizer particles. A good all-purpose potting soil.
- Orchid mix - contains bark suitable for many types of orchids.
- Cactus soil - contains sand and mimics soils found in cacti's native environment
A simple recipe for potting soil is to mix equal parts of peat moss, perlite, and sterilized garden soil together. Sterilizing garden soil requires heating it; the Oregon Cooperative Extension offers instructions on how to sterilize garden soil to make it suitable for use as potting soil.
Choosing Bagged Potting Soil
Now that you understand potting soil vs garden soil, it's time to choose bagged potting soil for your needs. Bagged potting soil must be both functional and economical. You don't want to spend a fortune on it, but you do want to make sure you buy the right type for your needs. Avoid bagged potting soils that are excessively heavy. These soils are either filled with extra sand, which adds weight, or water has entered the bag. Water in and of itself won't harm the soil, but it will make the bag soggy and hard to handle. It also created an environment where bacteria can breed, and the fact that water has entered the bag indicates that the soil is no longer sterile.
When to Use Potting Soil vs Garden Soil
Use potting soil marked for seed starting.
Do not use without sterilizing; may contain bacteria and fungi that can kill seedlings.
Use soil marked for each type of plant such as cacti, African violets, others.
Do not use for house plants. May contain insect eggs that can hatch inside the home.
Suitable for outdoor container gardening.
Suitable for outdoor container gardening.
Good Soil Makes for Good Plants
Potting soil vs garden soil has various advantages and disadvantages. In general, if you're starting seeds indoors or transplanting house plants, a sterile potting soil mixture is best. If you're potting up containers for an outdoor container garden or window boxes, you can probably use plain old garden soil.
Good soil makes for good plants. A rich, well drained, fertile soil helps plants grow big and strong, and that translates into abundant vegetables and flowers for your garden or beautiful blooming house plants. Starting plants off in the right kind of soil gives them a boost and helps them remain healthy.
© 2013 Jeanne Grunert
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