Pensacola News Journal

For: Saturday, September 20, 2003

By: Daniel E. Mullins

Extension Horticulture Agent

Santa Rosa County

Rain Gardens are Helpful to People and the Environment

Do you have a man made depression or a bio-retention area in your yard? If so, you will quickly learn that this is not a place to do conventional gardening. Likewise, due to rainy periods when the soil is saturated with water, attempts at growing the standard turf species usually result in disease infected, rotten grass followed by assorted weeds.

Instead of struggling with a retention area, use it to the landscape’s advantage by establishing a rain garden. A rain garden is defined as an area that collects runoff from the roof, driveway and lawn, temporarily stores it and permits the water to be filtered and slowly absorbed into the soil.

Planting a rain garden can be the individual home owner’s contribution to cleaner water and an improved environment for everyone. There are many benefits. A rain garden decreases the amount of water lost to runoff, provides valuable wildlife habitat, contributes to the beauty of the neighborhood and helps to protect against flooding and drainage problems.

The rain garden is planted with vegetation that can tolerate alternating wet and dry conditions, and is used to replace these seasonally wet areas in the lawn where turfgrass does not grow well.

Creating a rain garden can be as simple or complex as you wish. The use of native plants makes sense and a naturalistic, informal style of plant arrangement is suggested rather than a formal style.

Proper plant selection is extremely important when designing a rain garden. The species used must be tolerant of two soil moisture extremes - being inundated with water during wet periods followed by periods of spring and fall drought. Plants that are suitable for the rain garden include cinnamon fern, spider lily, cordgrass, butterfly weed, may haw, goldenrod, oakleaf hydrangea, elderberry, saw palmetto, gallberry, sweetbay magnolia and the Florida red maple.

The garden can be quickly filled by spacing plants close together, with plans to thin them later. Provide adequate space for larger growing shrubs and trees. Annuals and perennials can be used to fill in the area initially. Don’t be afraid to mix plants and use grasses. Select plants and colors that will attract wildlife. Some experimentation will be required.

Weeds are generally a problem for the first year. Eventually the newly established plants take over by crowding out most weeds. After a year or two, you might find that your water levels are not as you thought. If that happens, reconstruct or replant areas that aren’t doing well.

Another alternative, the radical approach, is to quit mowing these low areas that retain water and see what happens. Some miraculous things happen in nature. You will note the reestablishment of native plant species that occurs over time. Herbaceous plants grow the first year, followed by a natural progression toward the woody perennials, shrubs and trees.

Note: This discussion concerning rain gardens is in no way meant to discourage the use of lawn grass where it performs well. A healthy lawn prevents erosion, allows for the absorption of water and prevents many pollutants from reaching ground and surface waters.

Question of the Week: My crape myrtles grow well and look healthy, but flower very little. Why do some crape myrtles not flower much?

Answer: There are several possibilities. The crape myrtle is a sun loving plant. It flowers best when exposed to full sunlight all day. Those grown in shaded locations usually make long, lanky growth and flower little.

Reducing the amount of fertilizer sometimes increases the amount of flowering. High levels of nitrogen can keep the plants in a prolonged vegetative, or growth stage not allowing them to go into the reproductive, or flowering stage.

Make certain that lawn weed killers are not applied nearby, as some can enter the root zone and have negative effects. Also, check the base of plants to make certain that no bark damage has been done. Free standing crape myrtles often suffer from “string trimmeritis” and by being repeatedly bumped by the lawn mower. Any practice that places stress on the plants can reduce flowering.