What is soil testing? Do you need a chemistry degree? Do you really need to do it to grow healthy flowers and vegetables? Soil testing is much easier than you might think and very important for the health of your garden.

The pH of your soil is the single most important factor in garden health, says Pam Rouhier, garden specialist at the Grange Co-op in Medford. If the soil's pH is not right, plants cannot pull necessary nutrients into their root systems.

A soil with a pH of 0 to 7 is more acidic and one with a pH of 7 to 14 is more alkaline, with 7.0 being neutral. Most common vegetables and garden plants thrive in soils in the 6 to 6.5 range, but some have more extreme preferences. Plants that grow well in acid soil include azaleas, rhododendrons, conifer trees and blueberries. Others, like clematis and lilac, prefer a more alkaline soil. Check the tag of the plant you are buying or ask a nursery person what your plant needs.

A common mistake Rouhier sees is rhododendrons or azaleas planted near a patio, sidewalk or house foundation where lime from concrete leaches into the soil. If your plant doesn't look good, its leaves are yellow, it doesn't blossom, or its blossoms mold or fall off, check your soil pH.

How do you do that? A pH-only test kit costs about $4. Take a sample of your soil, add to a vial with water and the pill included, shake it up and compare the reaction to the color graph on the package.

You can test soil to find out what nutrients are lacking, according to master gardener Carol Robinson from the Oregon State University Extension and Experiment Station in Central Point. More comprehensive kits test for nitrogen, phosphorus and potash, the three components of most fertilizers, and cost about $15.

Ideally, you should test the soil in a new garden bed before you put in plants or amendments. In established gardens, test before you add fertilizers. And make sure to test the soil in different places in the garden, says Rouhier. She likes to test in the middle of summer after additives and fertilizers have had a chance to work.

Once you've tested your soil, you know which ingredients to add to improve it. The addition of lime raises the pH (alkalinity) of soil while additional sulfur decreases the pH (increasing acidity). Organic gardeners can add bone meal and hardwood ash to raise soil pH or composted leaves, cottonseed oil, peat moss and aged steer manure to lower pH.

Don't expect an immediate fix. The chemical correction can take months, but you'll be glad you got out the test tubes. Next year's flowers and veggies should be profuse, beautiful and yummy. So, get that test tube and in the words of an old song, "shake it up, baby."