Periwinkle blue flowers, Plumbago flourishes in northeast Florida

JORDI: It helped to have a clipping of your shrub because I was able to detect mites which contributed to the shrub's decline. Consider some light pruning to remove heavy infestations on the limb tips along with horticulture oil sprayed directly on the plant leaves and stems. In addition, applying imidacloprid as a soil drench around the root area should help you control the mites. This chemical is taken up by the roots and goes through the vascular system ending up in the leaves and flowers. When the insect feeds on the plant tissue they take up the chemical and die.

We would not recommend you use this on all your plants but only those having insect infestations. Both the horticulture oil and imidacloprid can be found at most any garden center.

Plumbago, Plumbago auriculata, is best grown in zones 9-11. Remember those of you along the east part of I-95 are in cold hardiness zone 9a while those of you on the west part are in 8b. This means plumbago may die back completely if temperatures become too cold for long periods of time. In your case, since you are in zone 8b, this plant is slightly out of its comfort zone. This may place some undue stress on the plant making it may be more susceptible to insects or disease. But do not be discouraged, as it may well survive in your area although it does have one strike against it. Be sure to protect plumbago if temperatures drop below 32 degrees, especially during its first few years in the ground. Allow for plenty of room as it can reach heights of up to 10 feet with an equal spread. This makes it a poor specimen for directly up against the house.

Plumbago prefers part shade to part sun but I have seen it planted in full sun with some success too. Its periwinkle blue flowers are unusual in the plant kingdom making it a prized plant. The flowers bloom from spring through the fall.

Plumbago is slightly drought tolerant, but does not need to be watered as often as lawn grass. It can live in most any soil condition making a wonderful plant for new home sites. However, if the soil pH is too alkaline the leaves will turn yellow from mineral deficiencies. There is a white flowered plumbago cultivar called ‘Alba'.

QUESTION:  In my neighborhood I have noticed some lawns are already totally brown and dead while others are still green. All of the lawns are St. Augustine grass so how do you account for the differences? DC

JORDI: First, simply because the grass blade is brown, does not necessarily mean the grass is totally dead. It is important for the stolon, which is the above ground stem, and roots to be kept alive during the winter months. If the stolon is still green and the roots are healthy, your lawn should come back once the spring returns, which is usually March.

We would recommend cutting back on watering during the cooler months to once every 10-14 days to ensure the roots receive ample water. Of course, cut back on irrigation it rains. Do not be tempted to keep the same watering schedule as during the growing spring and summer months because this can contribute to disease issues.

Winter is also not the time of year to apply nitrogen to the lawn – allow your lawn to go dormant from October through February here in the Northeast part of Florida. I know some of you from colder climates are thinking this is not winter at all. Well, this grass is a warm season grass and as far as it is concerned – this is cold!

There are many different cultivars of St. Augustine grass – some are more tolerant to the cold than others which mean some may turn brown earlier than others. However, taking care of any St. Augustine grass properly at all times of the year absolutely determines how well it is able to tolerate stresses such as drought or cold. If you are concerned about your grass, please call the Yulee satellite office (904 548-1116) for a grass “check-up” appointment. In a nutshell the following are the proper care instructions:

-- Mow at the highest height for the cultivar

-- Irrigate evenly (1/4 – ½ inch) from 6am to 10am, once every 3-7 days in the summer, once every 10-14 days in the winter, calibrate your irrigation system.

-- Use 15-0-15 slow release fertilizers March, May & September

-- Avoid broadcasting insecticides, herbicides and fungicides annually but instead spot treat once a firm diagnosis has be given

-- Call your local County Extension Agent for more specific information regarding appropriate care of lawngrass and specific fertilizer and irrigation ordinances.

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Rebecca Jordi

(904) 548-1116 or (904) 879-1019,  http://nassau.ifas.ufl.edu