Growth regulators can reduce fruit development on trees, shrubs

Q: We have a tree that produces very large acorns. They are a tripping hazard, and the acorns also prevent me from using the mulcher on the leaves. A friend told me there is a spray you can apply to the tree that will prevent it from producing acorns. Can you tell me if there is such a product and, if so, how to apply it? The tree is massive. It’s 50 feet high, so I couldn’t cover all of it.

A: This is the time of year that many people regret having large trees in their landscapes. Besides oaks, there are large nuts and messy fruit on sweetgums, apples, ornamental pears, olives and many others.

There is a product that may help. It is called Florel. It is a growth regulator that has interesting effects on different kinds of plants. The effects are beneficial in some cases and detrimental in others.

The label on horticultural products tells us a lot about the product’s use. Many people don’t read labels past the “how much product to use” paragraph.

The Florel label says it “will reduce or eliminate undesirable fruit development on many ornamental trees and shrubs such as: Apple, Carob, Crabapple, Elm, Flowering pear, Flowering plum, Horsechestnut (Buckeye), Oak, Olive, Sour Orange, Sweetgum, Sycamore and others.”

The label also describes the proper timing for this beneficial product. The trees must be sprayed in the spring, usually when the flowers or fruit are just starting to develop. You need to follow the label’s directions for your specific kind of tree.

Oak trees have catkins for flowers that many people will not even notice. The flowers need to be sprayed, so someone will need to climb up into the tree, as any spray from down below will drift onto a lot of other plants and potentially cause a lot of problems. You may need to call an arborist who has a bucket truck to get into the tree, and you may have to cover the plants under the tree.

Uncovered portions of the tree will still produce acorns.

Some of the effects of Florel on underlying vegetation are beneficial for nursery stock and flowering plant growers. It will increase short lateral branches; it can prevent flower buds from growing; it may cause plants to drop their leaves.

This may not be good in the landscape, but shorter plants with more branches that can be brought into bloom later are beneficial for growers of flower shop azaleas, chrysanthemums, geraniums, poinsettias and other flower crops.

Some people grow a lot of plumeria plants. I have several in pots that I take indoors for the winter. Over the winter, these plants will slowly drop all their huge leaves, creating a moldy mess. Florel will cause the plants to drop all their leaves within a week. Sprayed before they are brought indoors, the plants will drop all their leaves and prevent a mess inside. A side benefit is that Florel will also stimulate the appearance of flower buds.

It will also help many bromeliads initiate flower production. These plants will often not flower for several years if left to their own devices. If you have Anana, Aechmea, Billbergia, Neoregelia or Vriesia plants, give Florel a try.

Another use for Florel that many people will appreciate but probably don’t know about is that it will kill dwarf mistletoe shoots in pines and spruces, and it will kill leafy mistletoe in deciduous trees.