Ask the Plant and Pest Professor: Holly Berries, Struggling Gardenias and Fruit Trees

Question #1: We have a number of holly trees and shrubs on our property. This time of year they are usually loaded with berries. I am very disappointed because this year they hardly have any at all. Do you know what may have happened to the berries?

Answer #1: There are a few possibilities why your hollies do not have any berries now. If they never produced any at all this season most likely the reason is environmental. Drought stress and lack of pollinators when your hollies were flowering last spring are two examples of environmental problems. If the berries recently disappeared, a hungry flock of cedar waxwings or robins may have gobbled them up. Next spring if the weather is dry when they are flowering try to give the plants some supplemental water. Also do not use insecticides around the plants as they may harm beneficial pollinating insects.

Question #2: During the summer I received a gardenia that was loaded with beautiful white flowers. Since I moved it indoors for the winter it has not bloomed. In fact it is struggling. What is the best way to take care of it until I can move it back outdoors in the spring?

Answer #2: Careful placement of gardenias indoors is very important to keep them healthy. Maximum sunlight, high humidity, cooler temperatures and even watering are essential. Never place them near a heat vent where the hot, dry air will stress them out making them susceptible to spider mites and scale insects. Placing the container on a tray of moist pebbles is the most practical way of increasing the humidity around them. They are reluctant to flower indoors. However, cooler temperatures, about 55 degrees F in the evening, will promote the formation of flower buds. Water when the top ½ – l inch of soil feels dry and fertilize periodically starting in late February with a water-soluble fertilizer labeled for acid loving plants. After the danger of frost has past place it back outside. Initially place it in a shaded location then gradually move it to where it will receive more sunlight.

Question #3: My daughter moved into a home with some fruit trees on the property. There is a peach, a couple of apple and pear trees. She asked me to help her take care of them. I have heard that fruit trees need to be sprayed with dormant oil in the winter. Can you please explain what I need to do?

Answer #3: Dormant oil is a heavier concentration of horticultural oil. It is a refined petroleum product that has had impurities filtered out. Oils are low in toxicity and are sprayed on fruit trees in the fall or early spring while the trees are still dormant. Dormant oil controls the eggs and overwintering stages of various mites, aphids and scale insects. Sprays should be made according to the product label and when temperatures are expected to remain above 40 degrees F for a 24 hour period after spraying. Look on the label of the horticultural oil product you choose for the dormant oil dilution rate as most labels list both for use in the growing and dormant season.