Growing Better Q & A

Useful Tips
A sample of the many useful tips you will find in each issue of Florida Gardening.


In scattered areas of my St. Augustine grass, I've noticed patches where the leaf blades are turning a light purplish-red. What's wrong?

This developing red pigment in the leaf blade is caused by a reaction to lower temperatures. In winters when it is very cool you will see a lot of that. It is always heaviest in areas of the lawn that are under the most stress. In spring, when temperatures are consistently in the 70s again, the green will return. Often the grass will be red over such a big area that it looks like it's been sprayed with a red dye, but this is always related to low temperatures. The farther north you go, the more of it you'll see.
- Submitted by Gene Joyner, Palm Beach County (SE)


My magnificent Christmas cactus was given to me 25 years ago by an 85-year-old man who brought it from Germany. It was his mother's plant and is approximately 150 years old. Is longevity normal for this plant?

Actually, Christmas cacti are more likely to be killed by kindness than by age. When given the right care, however, they often outlive their caretakers. A large, mature Christmas cactus can develop what appears to be bark, and is capable of producing hundreds of blooms. The care required by the plant is well worth the effort.
- Submitted by Stephen Brown, Lee County (SW)


My mango tree is blooming and I'm concerned that a cold wave will damage emerging fruit.

Not to worry. This early bloom is normal and rarely produces sufficient fruits of consequence. A February-through-March bloom will be the one to produce the expected summer crop.
- Submitted by Stephen Brown, Lee County (SW)


This is the first year my loquat tree has fruited. How do I know when the fruits are ripe?

Loquats or Japanese plums (Eriobotrya japonica) are a forgotten fruit for the most part. The tree grows throughout Florida and fruits in all but the very cold regions. The fruits are ripe when they turn from green to yellow or orange and soften. Not all are tasty varieties, but most have a pleasing flavor.
- Submitted by Tom MacCubbin, Orange County (C)


We have a lemon tree that produced hundreds of lemons this year. We have picked many, but an awful lot in various shades of yellow are still firmly attached to the tree. We have been told that you must pick every single fruit in order for the tree to produce next year. When should we take all the rest off? Last year the tree produced 3 lemons; the year before none.

You do not need to pick any of the fruits in order to stimulate flowering and new fruit set. New plant growth on both the Meyer and Bearss lemon trees are the source of new flowers and fruits. The heaviest growth occurs in spring and is usually followed by 2 smaller growth flushes later in the year. Thus, remaining fruits are 'moved' to older wood as the new flushes occur. New growth is stimulated by warmer weather and not hindered by left-over fruits. To take advantage of this physiological response, commercial growers often prune their lemon trees in order to stimulate new growth flushes and consequently higher yields. The variation in fruit color on your tree indicates fruits at different stages of maturity due to the 3 annual growth flushes. The increase in annual yields is proof that your tree is progressing well under your care.
- Submitted by Stephen Brown, Lee County (SW)


I've discovered on several of my large interior foliage plants white insects which have been identified as mealybugs. What is the easiest way to get rid of them and not damage the plant? Can I simply take them outside and wash them off with a garden hose?

There are a number of products available for mealybug control, but soap and water works. You can take the plant outside and wash off many of the adult insects and much of the white residue, but often some will remain, especially in the soil. Don't leave the plant out in the hot sun for very long as it is used to indoor conditions and will burn. Put it in a shaded area and treat with soap and water or a mild insecticide. Repeat the treatment in a few weeks if you still see insect activity.
- Submitted by Gene Joyner, Palm Beach County (SE).


Leaves on one of my phalaenopsis orchids are starting to shrivel. All the plants are treated the same. What could be the problem?

Older leaves of phalaenopsis orchids may shrivel as they decline. If too many of the leaves appear to have similar symptoms, there may be a cultural problem. Make sure the plant has good drainage to prevent the roots from rotting. It may be time to transplant the phalaenopsis into fresh orchid potting mix. Also, keep the orchid moist and in filtered light. Water when the growing medium starts to dry to the touch. Phalaenopsis orchids prefer a warm, moist site, but also need good air movement. Grow them in filtered sun in an airy site under a tree or shaded patio. Bring them indoors when temperatures below 55 degrees are expected.
- Submitted by Tom MacCubbin, Orange County (C)


I have planted and enjoyed many, many Mexican petunias. We now live in a condo and the Association has many rules and regulations. We were told to get rid of our plants because they are invasive and could take over.

The Florida Exotic Pest Plant Council (www.fleppc.org) lists Ruellia tweediana (Ruellia brittoniana) as a category 1 invasive pest. Their listing has no legal standing, but is a good guide to the plants we wish to eliminate or keep in check. Not a true petunia, Mexican petunia is native to Mexico. It spreads by seeds and underground runners known as rhizomes.
- Submitted by Stephen Brown, Lee County (SW)


I recently purchased a flowering maple plant. Should it be planted in the ground or left in the pot? What other care is needed?

Your new plant has a maple-looking leaf, but that's the only resemblance to a true maple. Flowering maple (Abutilon spp.) is related to cotton, hibiscus, and okra. Each has a bell-shaped, colorful flower. Like many other members of the Mallow family, it is cold sensitive and is best left in the pot in central Florida. Gradually increase the size of the container as the root ball enlarges. Water when the soil surface starts to dry, which may be daily during the summer. Also feed at least every other week March through October and monthly during the cooler times of the year.
- Submitted by Tom MacCubbin, Orange County (C)


I bought a Musa zebrina 'Rojo' for its striking variegated color. The plant is in a container on an east-facing lanai, but gets full sun all day. It is thriving, but the leaf tops are now solid green. What changed the color?

This plant is known as the red banana. Ornamental bananas and their close relatives, the heliconias, are native to the humid tropics where they grow as understory plants. Even in botanical gardens in the tropics, heliconias and banana-like plants are almost always grown under shade for best performance. Variegated plants are often sold as ornamental foliage plants. In certain species, increasing light increases the color contrast on leaves. However, in the case of this Musa, exposing it to such prolonged and intense sunlight is contrary to its natural setting. While it may grow well, it becomes just another green plant when contrasting hues blend together. Move it to a shadier location, increase watering, make sure the pot drains freely, and add several tablespoons of a slow-release fertilizer.
- Submitted by Stephen Brown, Lee County (SW)


Is this a good time to plant impatiens in a large pot on a shady porch?

Impatiens tolerate all but freezing weather. Just be ready to move the container indoors when temperatures in the low 30s are expected.
- Submitted by Tom MacCubbin, Orange County (C)


I have a beautiful gardenia bush. It has dark leaves and blooms often. However, the flowers are small. Are there different varieties of gardenias, or is my plant lacking something? Most of the gardenias I have seen are twice the size of the flowers on mine.

The popularity of the common gardenia or cape jasmine (Gardenia augusta), has led plant breeders to develop plants with varying flower and leaf sizes, fragrance, color, and growth habits. Plants with these variations are known as cultivars, or cultivated varieties. Unless your soil is exceptionally dry, there is no other likely reason for the small flower size, except variation as expressed by different cultivars.
- Submitted by Stephen Brown, Lee County (SW)

I have a potted gardenia which is not grafted and is outgrowing its container on my patio. Can I plant it outside in the ground and have it survive and thrive?

Most ungrafted gardenias will last only a short period in an average landscape due to problems with nematodes or soil diseases. Gardenias bred for landscape purposes are usually grafted on a nematode- and disease-resistant rootstock. You can enjoy your gardenia for a few more years as a container plant by either pruning it back or moving it into the next size container.
- Submitted by Gene Joyner, Palm Beach County (SE)


We have several pine trees around our Pine Island property and it is time-consuming to pick up several barrels of cones large enough to shatter lawnmower cutting blades. I’ve heard that female pine trees do not have pine cones, or not as many as male trees.

Fruit and seed production are the result of plants engaging in sexual activities known as pollination. Depending on the species, some flowers on a plant only produce pollens and are known as male flowers. Other flowers, when pollinated, produce fruits and cones and are known as female flowers. To complicate matters, some plant species have male and female flowers confined to separate plants which are considered to be either male or female plants. Although both male and female plants flower, only the female plants produce fruit. Examples of dioecious species (with separate male and female plants), include mahogany, southern magnolia, and the Canary Island date palm. It is more common, however, to have both male and female flowers on the same plant. All plants of these monoecious species will bear fruits or cones. Monoecious trees include slash pines, common throughout south Florida, black olives, oaks, and crape myrtles. Your pine trees are monoecious and cannot be separated into male and female trees. Your problem will continue unless selected trees are removed.
- Submitted by Stephen Brown, Lee County (SW)


My palm tree fronds are being eaten away. The termite-like activity is entirely on the leaves. What is causing this?

The palm leafminer, also known as the palm leaf skeletonizer, is out of control in some neighborhoods. The tunneling between leaf surfaces that produces debris much like that of termites is the work of cater-pillars.

The insects cover themselves with a silken web which gives protection from predators and pesticides. Usually the damage is restricted to a few fronds that can be cut from the palms with minimal harm to the plant.

Sometimes numerous fronds are affected and the caterpillars seem to spread quickly. Obtain control with an insecticide labeled for chewing insects and follow instructions for palms or ornamental plants.
- Submitted by Tom MacCubbin, Orange County (C)


What is the name of the tree now blooming with large blue flowers?

It is the jacaranda (Jacar- anda mimosifolia), a monoecious, deciduous tree with a fine-textured leaf. The jacaranda will drop most or all of its leaves just before flowering and will re-leaf while still blooming.
- Submitted by Stephen Brown, Lee County (SW)


My centipede grass gets circular areas that grow larger and larger, killing the grass as they grow. The grass starts to grow again in the middle. Could it be a UFO sighting?

You’ve been watching the Sci-Fi channel, haven’t you? The description you give is a textbook example of fungal growth, which can be controlled by fungicides labeled for centipede grass. As always, be sure to read the label before applying any chemical to your lawn. Centipede grass is a low-maintenance grass that does not respond well to excessive use of fertilizer, especially nitrogen. Centipede grass is a paler green than St. Augustine. If you fertilize it with high levels of nitrogen, it will temporarily "green up," but you will have future problems. It prefers the soil pH to be 5.0 to 5.5, which is very acid. If your soil pH is not low enough, the grass will appear yellow (because of a lack of iron). When the grass starts to yellow, most people add more nitrogen, which can potentially cause the grass to become susceptible to insect and disease damage. When you fertilize, use a fertilizer containing elemental sulfur, which will help lower soil pH. A good fertilizer program would include applying iron to the grass in April and July for high-maintenance lawns, or in May and August for low-maintenance lawns. Contact your local extension service for the University of Florida/IFAS publication on centipede lawns.
- Submitted by Rebecca Jordi, Nassau County (NE)


We will be leaving Florida soon and always do some major trimming of plants before we leave. We have been thinning our birds of paradise. Two are in fine shape, but the third one seems to have a problem. Some of the leaves have white spots on the back and yellow discoloration on the top. The plant does not look healthy, even though lots of flowers are popping out. I must admit I have never fertilized the birds.

These white spots on the underside of leaves are independent of fertilizer application and irrigation. This South African native, Strelitzia reginae, is susceptible to a white scale insect that damages the foliage in the manner you’ve described. The insect feeds on green chlorophyll sap, which results in yellowing of the area where feeding occurs. Many insects and diseases are specific to certain host plants. Chances are, in your pruning and thinning of this infested plant, the scale will not be carried to other healthy plants of different species by infected cutting tools. However, the scale may be spread to healthy birds of paradise by cutting tools. There are many systemic insecticides recommended for the treatment of scales. It would be best to make 2 applications of an appropriate insecticide some 3 weeks apart to all the birds of paradise. Inclusion of a spreader sticker in the solution will increase the effectiveness of the insecticide.
- Submitted by Stephen Brown, Lee County (SW)


Four magnolias were planted in an island at the back entrance to my subdivision. One tree has died and another is dying. What could have caused this?

Magnolias are quite hardy and well-adapted to northern Florida. Because they have few pests or diseases that will kill them, curiosity got the better of me and I went to see these trees for myself. There was no indication of borers, but one tree had an infestation of piercing-sucking insects and, as a result, was covered with sooty mold. This insect infestation may be the result of the tree being under stress. The island is probably too small to accommodate 4 large magnolia trees, although 2 of the trees are still doing well. I suspect the soil depth is insufficient for this type of tree. Concrete or asphalt from construction of the island may be preventing the tree roots from developing. In addition, the dying tree appears to have been planted too deeply. The top root should be at or just below soil level and I could not locate it. If the homeowner association wants to plant something else in this location, I recommend that they determine the depth and breadth of the soil first. The mature height and branch spread of the remaining magnolias should be considered before making any choices. Perhaps smaller tree-like shrubs, such as dwarf crape myrtle or oleander, would be more suitable for this site.
- Submitted by Rebecca Jordi, Nassua County (NE)


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