What is a rain garden? The small community where we vacationed was dotted with pretty little gardens, each with a marker that said, “This rain garden is sponsored by …” None of us had heard of that before and are curious.

 

In light of the heavy rains we’ve been experiencing lately, your question could not be more timely.

Rushing storm water picks up and carries pollutants like auto oil, pesticides and fertilizer and debris, like nitrogen-rich leaf litter and lawn waste into our storm drains. From there, they go into our rivers and lakes. A rain garden is essentially a garden of native flowering plants, sedges, rushes and grasses planted in a small depression in the landscape, designed to temporarily hold stormwater runoff from surrounding hard surfaces, and allow it to percolate into the ground. As water moves downward through the soil, chemical and biological processes filter and break down many pollutants. Over time, excess water evaporates into the atmosphere. Because of the way it is constructed, “a rain garden allows approximately 30 percent more water to soak into the ground compared to a conventional lawn” according to information found in a publication by the City of Tallahassee.

In addition to aiding pollution control, rain gardens provide some flooding protection, and reduce soil erosion.

If your lot doesn’t enjoy a naturally sloping area or depression, you can build a rain garden as an attractive and Florida Friendly Landscape feature. There are publications by the University of Florida that provide considerations about where to place and how to dig a rain garden. Though written for Central Florida, the basic principles outlined in “Rain Gardens: A Manual for Central Florida Residents” will apply to North Florida as well. There’s even a list of plants that will survive having both “wet feet” and occasional dry spells.

For the butterfly enthusiast, you’ll find many on this list to be native plants attractive to butterflies and other wild life: bit.ly/1CO3vL8.

One last caveat about responsibly maintaining your rain garden. As we are all aware, standing water provides a breeding ground for mosquitoes, and thus for disease. Bacillus thuringiensis israelensis (Bti) is a great larvicide available in granules, bits or dunks at local hardware stores and nurseries, and should be used wherever you have standing water, such as rain gardens.

My French mophead hydrangeas are just about done for the season. Is there anything I should do now to help them look good next spring?

Even though hydrangeas need little to no pruning, if they’re about to outgrow their allotted garden space, mid- to late summer after the blooms have faded is the time to prune them into submission. Start by removing all diseased, weak, or dead wood. Of the health branches remaining, take no more than one-third to one-half of each main stem. Weaker shoots, both old and new, should be removed at the base. Pruning now allows the plant sufficient time for regrowth, and forming flower buds for next spring.

Hydrangeas are low maintenance plants, but will appreciate an application of 6-6-6 or 8-8-8 fertilizer in the spring at a rate of 1½ to 2 pounds per 100 square feet of bed.

If you love hydrangea as much as I, you might consider extending the blooming season by adding a different variety to your garden next spring.

Panicle hydrangea (Hydrangea paniculata) are being used more often in our area. They are smaller leafed then the French hydrangea and have multiple trunks. You may have noticed the “Limelight” variety in local nurseries. They can grow quite large, sometimes and can even be trained as a small tree. The showy creamy-white blossoms last longer than French hydrangeas and turn a bright, chartreuse green. Later, in fall, they fade to purplish pink that continue to add interest to the garden.

Another large plant and my latest obsession is the native oakleaf hydrangea (Hydrangea quercifolia). The leaves are deeply lobed and resemble large white oak leaves. Found along stream banks and bluffs in Florida, Georgia and Alabama, the oakleaf grows to a height of 6 to 10 feet. In the summer, it has huge cone-shaped clusters of white flowers that stay on the plant for months. In time, the white changes to a light pink or purple. The 8- to 12-inch long and wide leaves turn red, bronze or purple in the fall and often stay on the plant well into winter. Finally, in winter when all the leaves have dropped from this deciduous plant, the peeling bark of the trunk continues to provide interest.

If your garden is too small for such a big plant, keep in mind that dwarf varieties are available. Try one of the more compact cultivars like ‘Pee Wee.’

And, as an aside, for you gardenia lovers, mid- to late summer is the best time to prune them, as well.

Paula Weatherby is a master gardener with the Duval County Extension Service and the University of Florida/IFAS.