JULY
2002

 

 

 

By
Beverly Shaw
 
Advanced
Master Gardener
Purdue University

 

 

 

 

 

7-3-02

Question and Answer

Q.  An insect is killing my schefflera. It gets white, fuzzy-looking places on it that feel soft, and you cannot see the insect that is working on it. Finally, it will kill the leaf if not removed. I wash the leaves from time to time with soap and water, and last time a little bleach. It works for a while. I even tried a fungus product and worked it in the soil after giving the plant a bath. Help! I like the plant but need to know what to use on it. -- Janice Corwin

A.  Mealybugs congregate where the leaves attach to the stem or around major veins on the undersides of leaves. They appear to be dusted with a fine, white flour and, sometimes, have long, waxy filaments extending from their bodies. They are slow-moving, wingless insects that are protected by their waxy covering. They remove plant juices with their sucking mouthparts, resulting in yellow, distorted leaves.

Spraying plants with forceful streams of water often washes off and kills smaller insects. Individual insects can be removed with a toothpick or tweezers. Or you can wet or remove each insect with a cotton swab dipped in isopropyl alcohol. You must recheck the plant every two weeks or so to be sure you have removed all of the insects. Alternatively, you could treat the plant with an insecticide. Resmethrin and insecticidal soaps are listed for mealybugs. You can make your own insecticidal soap by mixing 4 teaspoons of dishwashing liquid per quart of water. Don't spray on any flowering plants or particularly sensitive plants like African violets or ferns. 

The fungicide you applied will only protect a plant from fungal pathogens and will not have any affect on insects or other pests. Be sure to identify the particular problem before using pesticides. It's better for your health, the environment, the plant in question and your pocketbook!

Q.  I have tried and tried to identify this plant by searching in many wildflower, weed and herb books but can't identify it. Since I found it near my dad's woods beyond the cornfield, I do not know what color the dense spikes were, as we only go to the area after harvest, which is after frost.

I am sending an end seed piece, a piece of the stem and a sketch of the plant. Here are the clues for identification: it grows 6 feet tall, has a square stem and has 4-6-inch erect flower spikes.

The closest I've come to identifying it is Agastache nepetoides, but it doesn't get that tall, so that can't be it. -- Janice Teel, Mentone, Ind.

A.  Good work! I often receive plant descriptions that are missing important bits of information, making it impossible to identify the plant. And you actually solved your own mystery, since the plant in question is, indeed, Agastache nepetoides or yellow giant hyssop. This is a perennial that can reach a height of 7 feet. (I'm guessing that you had a reference that said otherwise, but it really can!) The flowers are yellow-green, sometimes almost white, and appear from late summer into early fall. While this is most often found growing wild, it can be a nice addition to the back of the perennial garden, since it has an extended bloom time and some architectural interest.

Agastache is a member of the mint family, which is easily recognized by the square stem. Nepetoides means it looks like catnip (Nepeta). It is attractive to bees and butterflies and prefers thin woods, thickets and openings.

Q.  About 10 years ago, I purchased four hardy kiwi plants that were supposed to be three female and one male. They have grown very well -- but no fruit!

I'm having a similar problem with persimmons. A friend gave me two trees about 8 years ago, and they have grown very well -- but no fruit! I check every year for blossoms, but I don't think I see any. I don't understand the "birds and bees" of these plants. Can you help me? -- Ozzie Luetkemeier, West Lafayette, Ind.

A.  The kiwi vine that produces fruit like that in the grocery is Actinidia deliciosa, and it is dioecious, meaning male and female plants are required for fruit production. Even the supposedly self-fruitful cultivars do better with a pollinator. Actinidia deliciosa isn't really hardy in Indiana. If the plants do survive, the flower buds would almost always be killed during winter and early spring freezes.

There is a hardier, self-fruitful kiwi vine, Actinidia arguta, but the fruits are much smaller, like large grapes. If this is the cultivar in your garden, you should have better luck. Sometimes, they don't produce for the first 5-9 years, but you've passed that hurdle. I suspect that yours are all of the same gender (are all four still surviving?), or they are succumbing to late spring frosts. While the roots are hardy to –30 F, the tender shoots are extremely susceptible to spring frosts. You may want to cover them with a sheet or spun polyester blanket (available through garden catalogs or in garden centers) during frosts. More information on hardy kiwis is available at http://ssfruit.cas.psu.edu/HardyKiwi.htm.

The native persimmon is botanically known as Diospyros virginiana. The species is native throughout the lower Midwest and the southeastern states. It is known to be hardy to temperatures of -20-25 F without apparent winter injury. The native persimmon is a small tree, but may often reach a height of 40-50 feet and occasionally even larger under ideal conditions.

The greenish-yellow flowers are borne on very short stalks. The staminate (male) flowers are usually borne in threes, are about one-fourth to one-third inch long, and usually contain 16 stamens. The pistillate (female) flowers are borne singly, ranging one-half to three-fourths inch in length with four two-lobed styles.

The persimmon is dioecious, that is, each tree produces only either male or female flowers. This means that both male and female trees are usually necessary to produce a crop of fruit. The native persimmon is regularly dioecious, with male trees producing only staminate flowers and female trees producing only pistillate flowers. Only in rare instances are trees self-pollinating.

When planting seedling trees, be sure that you have female trees, if fruit is desirable. This can only be proven by fruiting the trees. For positive fruiting, both male and female trees should be planted. The exception is that in the natural range of the persimmon, adequate wild trees will be available for pollination. As an added thought, if the trees are intended for ornamental purposes only, and fruit is not desired, then a male tree might be selected to eliminate the problem and mess of dropping fruit.

It is probably best to obtain budded or grafted trees from a reliable nursery to be sure of getting the type of trees you want and trees with desirable fruit characteristics.

Care of the persimmon is minimal. Fertilization is not usually necessary, other than the fertilization that would normally be given to a lawn. Pruning is not usually needed, except to limit tree size, and to correct faults such as dead or broken limbs.

Again, chances are good that you have two trees of the same gender, or they have not quite reached maturity. It can take 10 or more years for persimmons to begin fruiting, although some will begin much earlier.

The oriental persimmon, Diospyros kaki, is not native to Indiana and is not adapted to Indiana conditions. Hoosier winters are too cold to permit cultivation of this species, except in rare and very protected situations. It is not hardy below about 10 F. This is the species of commerce and is grown commercially in southern areas of California. The fruit ranges to 3 inches across and is seedless in most varieties. Nursery catalogs frequently advertise this species, but Indiana gardeners are cautioned against purchasing plants of D. kaki.

 

Contact: B. Rosie Lerner
Editor: Olivia Maddox,