Why does my celosia plant have flattened stems? 

This phenomenon is known as fasciation. Fasciation is most often recognized by the flattened, fused appearance of stems, but can also be seen in flowers, roots and fruits. Herbaceous and woody plants are both susceptible to fasciated growth. While fasciation affects the plant’s appearance, it has little affect on the health of the plant.

There are multiple causes of fasciation. First, it can be caused by a bacterium (Rhodococcus fascians) that mimics the plant’s natural chemicals for controlling cell growth and development causing the unusual growth. Second, it can be caused by physical damage to the meristem tissue where growth is initiated.

The physical damage to the meristem usually occurs when the plant is a seedling and may be caused by an insect, herbicide, or physical contact. Thirdly, fasciation can be caused by a recessive gene. This particular recessive trait was used by Gregor Medel when he did his genetic research on peas. Celosias commonly show this mutation. More than 100 vascular plants have been known to produce fasciated tissue.

What is making holes in my rose leaves?

The native leaf cutter bees are responsible for the semicircular holes cut into the margins of rose leaves. These bees are similar in size to honey bees, but are not aggressive and will not sting unless provoked. The leaf tissue they are removing is not eaten; they use it to line their nests. Female bees build nests in soft wood and pithy plant stems. Leaf cutter bees prefer the leaves of rose, green ash, lilac and Virginia creeper among others. Damaged plants are not seriously harmed.

They are just not as aesthetically pleasing. Insecticides are not effective. There are some parasitic insects that naturally control leaf cutter bee populations. To prevent susceptible plants from being damaged, cover them with cheesecloth or other fine netting material to prevent the bees from reaching the leaves. When pruning roses, seal the cut stem surfaces with a thumb tack, wax or white glue to prevent female bees from building nests in the rose canes.

My muskmelon plants have started to flower, but aren’t producing fruit.  Why? 

Muskmelon and other vine crops are monoecious. Monoecious plants have separate male and female flowers on the same plant. Male and female flowers are similar in appearance. However, the female flowers have small, immature fruits at their base.  Pollen is transferred from the male to the female flowers by bees and other pollinators.

When properly pollinated and fertilized, the female flowers develop into fruit. The first flowers to appear on muskmelon and other vine crops are usually male. Female flowers appear shortly thereafter. While the first flowers on vine crops seldom produce fruit, the plants should produce a good crop with favorable growing conditions. 

Is it necessary to water an established lawn during hot, dry weather? 

Cool-season grasses, such as Kentucky bluegrass, can survive long periods of dry weather. In dry weather, the shoots of the turfgrass plants stop growing and the plants go dormant. Dormancy is a natural survival mechanism for turfgrass. While the leaves have turned brown and died, the turfgrass roots and crowns remain alive. Generally, Kentucky bluegrass can remain dormant for four to six weeks without suffering significant damage. 

It’s best to water dormant lawns if the dry conditions persist beyond this 4 to 6 week period as the dormant turfgrass plants are in jeopardy of dying. Apply 1 to 1 ½ inches of water in a single application. Water again seven days later. The grass should begin to green up after the second application of water. 

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There are two high resolution photos available for this column:

DoubleDaisy6-7-06.jpg , [720 KB]

leafcutterbee.jpg,  [144 KB]