Winter is finally setting in all along the Gulf Coast, the region where Tropical Hibiscus are most likely to be found. Looking back at history, areas that don’t get frost the week of Thanksgiving will probably have at least a light freeze sometime in December.
So loosen & aerate any old garden mulch with a rake, then spread a thick new layer of mulch all around those Hibiscus plants. Pine bark mulch is readily available and inexpensive across most of the South. Cedar, cypress, and redwood mulch are more expensive, but resists decay and will last longer. Cedar mulch may also repel some insect pests. All types of natural mulch will act to insulate soil & roots, so cost and appearance may be the determining factors for many gardeners.
Also stock up on light fabric plant covering materials, or else prepare to move potted plants indoors. Plants should not be covered with poly plastic sheet, as cold penetrates it easily, condensation collects on it, and plastic film may freeze to plant leaves.
If you have a garden cart, check the tires for proper inflation. It isn’t a lot of fun to load a cart with heavy pots on a frigid evening, and then find that the tires are flat!
When frost is forecast, cover plants that must be left outside, and water heavily. Water from a hose is normally at a temperature of at least 60F, and loses that heat slowly. Soaking a garden or yard area gives it a reservoir of heat that will last through many hours of a cold night, helping to keep low-growing plants & roots from freezing.
Of course, if you have a greenhouse, tropical hibiscus can be kept warm and blooming all year ’round. However, before frost sets in, check electrical connections, heaters, door & window seals, etc. Winter weather is often windy, so greenhouse covers should also be checked for small tears that might quickly grow into major problems on a windy night. Poly repair tape can be used to fix most small holes and tears in greenhouse covers.