Enviromental Horticulture — Flowers & Houseplants


I bought a kalanchoe and transplanted it in the front yard where it has done well but stopped blooming. What can I do to encourage more flowers?

Keep up the good care and your plant should be in bloom for the Christmas holiday. The kalanchoe is what horticulturists call a short-day plant. This means it initiates flower buds when the days begin to shorten during the fall. Flowers in this group include Chrysanthemum, holiday cactus and poinsettia.

Kalanchoes stop flowering during mid to late spring when the days become longer again. You may notice plants flowering on the market at this time, but they have been tricked into bloom. Black cloths were pulled around them during the afternoon. Flower buds begin forming naturally during mid- to late October.


I can never get interior palms to do well in my home. Are they hard to grow?

Interior palms are not hard to grow; however correct palm selection is critical. Most plant retailers will sell Areca palms as interior palms. However, they will perform poorly inside the home. Chamadorea palms look very similar and yet they grow and thrive nicely under low light and other adverse conditions found inside the home. Bamboo and Pador palms are two Chamadorea type palms. You may also need to check for spider mites.


My African violets look very healthy but they don't bloom. What could the problem be?

Healthy African violets that fail to bloom are not receiving enough light. African violets require 1000 foot candles of light for 8 to 12 hours per day. Lower light levels for longer periods of time are also satisfactory. This light can be provided by natural sunlight or fluorescent lamps. Night temperatures above 75°F will also reduce flower production in African violets. They prefer evening temperatures of 65-70ºF.


The tips of my spider plant leaves turn brown and shriveled. What causes this?

Spider plants are sensitive to fluorine in the city water and boron in fertilizers and the result is a brown or reddish foliage tip. There is no control for this sensitive reaction in some foliage plants.


What is good potting media for my houseplants?

A good potting media for most interior foliage plants is 2 parts of a "ready to use" sterile potting mixture and 1 part perlite or coarse sand. There are also many pre-packaged sterile mixes on the market, which may be suitable. It is important that proper drainage, aeration and moisture holding capacity be provided for most interior foliage plants.


My petunias are wilting and collapsing even though I have watered adequately. What is the problem?

Damping off is a disease that commonly affects petunias and other bedding plants. This soil home disease characteristically causes a browning and collapsing of the stem at the soil level. Soil fumigants, applied prior to planting according to label directions, have proven effective. Several fungicides are labeled but may be difficult for homeowners to find.


My ferns have brown spots on the underside of the foliage. Is this an insect or disease?

These brown spots are spore masses, not insects or disease. These spores are the equivalent to seeds in higher plants. Fern propagation from these spores is very difficult since exact and controlled conditions are difficult to simulate for most home gardeners. Division of the parent plant is recommended for fern propagation, except tree ferns.


How do I get my Christmas cactus to bloom?

Both temperature and day length affect the flowering of these cacti. If the night temperature is maintained between 50-55ºF, flower buds will form regardless of day length. If the temperature is above 55ºF but below 70ºF, 13 hours of uninterrupted dark will cause buds to set. If temperatures are between 70-80ºF, 15 hours of uninterrupted dark will set buds. The short day treatment should continue until buds are well developed. (6-9 weeks).


Why do the buds on my Christmas cactus drop?

Flower bud drop results from rapid changes in growing conditions such as a sudden drop in temperature or light. Other causes include soil that is kept too dry or too wet, exposure to cold drafts or high night temperature.


I have a hosta houseplant with leaves that are turning yellow and dropping. Is this through a water or nutrient deficiency?

Although having beautiful foliage, hostas do poorly in local landscapes and are not good houseplants, as they need good light all around them. Make sure it's moved close to a window but without sun. Keep the soil moist, and feed monthly with a houseplant fertilizer.

It's better to plant it outdoors in the shade under a tree, as they need cold in the winter to be at their best.


My potted amaryllis has developed three bulbs. The older leaves are still green, and there is new growth. Should I divide the plant?

You have a number of options. Leave the bulbs in the pot to continue growth; put the cluster in a larger pot; or divide the bulbs into separate pots.

University of Florida studies show that digging bulbs from beds or a pot and allowing them to air-dry with the root system intact encourages flowering. If the plant has flowered well, divide the cluster and re pot them separately, taking off the older leaves.


I purchased a desert rose that looks as if it is growing in a pot that is too small. Can I re-pot the plant? What is needed to make it thrive?

Gardeners tend to keep desert rose plants a bit cramped. A container 2 to 3 inches larger than the base of the plant is usually adequate. If needed, your plant can be repotted to a larger container. Many gardeners like to keep their plants in clay pots that provide good drainage.

Set the plant so that the top of the root ball is exposed. Often an inch or two of the roots are set above the soil to give the plant a stressed look. Use a loose potting mix when replanting. Keep the plant in a full-sun location, and water when the surface soil begins to feel dry.

Also feed every other week with a household fertilizer March through November. No fertilizer is needed during the cooler winter months.


My holiday cactus is showing signs of a fungus. It has pink spots, and the branches are dying. What should I do?

The symptoms you describe indicate a root-rot problem. Too much water from summer rains may have encouraged the root rot. The pink spots normally mean the plant cannot take up needed nutrients, and the dying branches suggest a lack of water because of a poor root system.

Try repotting your plant in fresh soil. Use a potting soil from available from your garden center. Remove some of the old soil on the roots, and repot in a clean same-sized container. Often this treatment stimulates new root growth that can resist the soil-borne pests.

Fungicides are available to help control rot problems, but the cost would be rather expensive to save one plant. You might make a few cuttings just in case your plant continues to decline.


How can I grow bromeliads in an air-conditioned apartment? I have a large pot of them, but little by little, they are dying.

Move the container of bromeliads away from the air-conditioned breezes and to a bright location but out of direct sun. If the plants have central cups of foliage, keep them full of water. Also, try to raise the humidity a little near the plants by setting the containers on a tray of moist pebbles. Otherwise, bromeliads need minimal care.

Touch the soil in the container, and when it feels dry, it's time to water. Moisten the soil until water begins to run from the bottom, You can just about skip feedings in the home. Once or twice a year, mix a 20-20-20 or similar product at a quarter of the normal strength. Use it when watering and allow just a little to enter the central cups as you also wet the soil with the solution.


My Christmas cactus is in a 7-inch pot and growing over the sides. Is it too late to transplant it to a larger container?

A Christmas cactus, also commonly called holiday cactus, seems to like a cramped lifestyle. It grows best when the roots fill the containers and become a little pot bound. Presently, the plants are entering a flowering phase in which growth slows, and they won't need a larger container.

Even though your plant might overflow the container, it's probably best not to transplant it at this time. Also, water only when the surface soil becomes dry. If you provide too much water or use a too-large container, root-rot problems could develop. If transplanting is needed, wait until spring growth begins and give the plant a container that is only 1-inch in diameter larger.


I bought an orchid recently that did fine in my home until a week ago when the lower leaves started to turn yellow. What can I do to prevent the decline?

Find your orchid a bright spot in the home, but avoid all but the early morning sun. Then make sure the orchid has adequate moisture. Thoroughly moisten the growing medium once or twice a week. Often, you can lift the pot to feel when the medium is becoming too dry. If the home is dry, use a misting bottle occasionally to dampen the stems and roots between waterings.

An orchid in the home needs little fertilizer. Use a 20-20-20 or similar product at one-half the label rate to feed the plant every, other month during the warmer weather. Where possible, give the plant a break outdoors under a tree when it stops flowering. It will be much happier in the filtered light where it can receive frequent waterings and feedings. When blooms again are noted, move the plant indoors so you can enjoy the display.


We have an ornamental corn plant on the patio, and the ends are turning brown. Are we watering too much?

You are going to have to do a little detective work to determine the cause of the browning; any factor that restricts water uptake could be the cause. Logically, check first to make sure the plant has adequate water. A large plant on the patio might need water daily during warmer months and every few days during cooler weather.

Make sure the container has good drainage. If the holes at the base of the pot are too few or plugged, the plant might be staying wet. This would cause the roots to rot and the plant to begin to decline. In this case, a new container or at least repotting would be needed.

A generous feeding also could cause the decline. Keep fertilizer applications to once a month during warmer times of the year, and don't feed during winter. To make feedings easier, consider one of the slow-release products that meter out nutrients to prevent plant damage and encourage good growth.


We planted sunflowers that grew slowly and then started to form small blooms, but the plants were only a foot tall. Are we planting at the wrong time of the year?

You either have a slow learner or an undernourished plant. They need a light feeding every two to three weeks to grow tall and produce big flower heads. Sunflowers can be grown year-round even though they could be damaged by cold. Some varieties are dwarf in size but even these grow a few feet tall.


A corn plant in a shady area of our yard got nipped by the cold, and almost all the leaves have some brown areas. Should I cut it down and try to rejuvenate it or just remove the bad leaves?

Corn plants used for foliage with yellow and green leaves are a type of dracaena that like the shade but not the cold weather.

Certainly the brown leaves are lost, but your plant should recover to produce lots of new leaves now that the warmer weather has returned. The problem is most growth is going to be from the top.

If your plant is not very tall, then the best suggestion is to remove the old brown leaves and wait for the growth to resume at the top. Even if the plant is somewhat tall, the brown leaves can be removed to grow a single-trunk plant with a green and yellow top.

If you want growth from the bottom, then probably it's best to remove the top and allow new shoots to start from along the stem.

Often the plants don't look quite as good, at least for a while, with a thick trunk and one or two new shoots.

Over time, they should grow to conceal the thick stub left at the top and form a new central shoot. Also, if you decide to remove the top, it can be rooted to start another plant.