We have a Washington Hawthorne tree. Is there any way, chemical or otherwise to prevent the setting of berries? I've attached a photo. I believe it's a Hawthorne.
Boulder County Colorado trees and shrubs
Preventing or reducing fruit on ornamental trees and shrubs “Nuisance fruit” is a concern for many people including homeowners, landscapers, and park and city officials. The fruits and seeds of some trees and shrubs, such as buckthorn, mulberry, persimmon, and (female) ginkgo are unsightly, smelly, and have the potential to be a hazard when they fall on sidewalks, driveways, and other areas in a landscape. Foliar sprays are available to reduce or eliminate undesirable fruit development on ornamental landscape plants, but factors such as timing, plant stresses, environmental conditions, and lack of thorough applications may make complete control impossible. Results will vary with each chemical designed to eliminate fruit. FACTORS TO CONSIDER BEFORE SPRAYING Trees and shrubs are usually selected for landscape use based on their ornamental features, such as spring flowers, fall color, and fruit. All trees and shrubs produce some type of flowers and fruit, whether inconspicuous or showy. Fruit production is part of the plant’s natural development. A plant that produces a large amount of fruit may be a desirable ornamental feature or be used to feed wildlife. Despite the value of a flowering and fruiting plant, some people consider spent flowers and fruit that fall undesirable litter. There are several methods to remove fruit or prevent fruiting. Hand-removing spent flowers or small fruits will work on a small tree, but is not a practical solution for large trees or extensive plantings. Chemical or hormone-type sprays are a more practical method, but spraying your tree can be a costly and time-consuming venture. Consider the following before you decide to spray: Amount of fruit production. The amount of fruit a plant can produce varies from year to year. Many plants will produce heavily one year and lighter the next. Insect, disease, and damage to flower blooms can reduce fruit production. Hand-removal of spent flowers is one way to eliminate unwanted fruit. Plant removal. If maintenance is a problem, does the plant warrant keeping? Attempting to remove fruit will become a yearly expense of time and money. When all options have been considered, plant removal may be the best alternative, and replace with a plant that holds its fruit (i.e., some hawthorns and crabapples). Size of tree. If the tree is too large to do the work yourself, you may have to hire a licensed professional to achieve adequate results. Timing of application. Whether you hire a professional or do the work yourself, it is essential to spray at the proper time for best results. The “window of opportunity” varies with the species and cultivars (varieties) of a plant. WHEN AND HOW TO SPRAY Timing. The window of opportunity for chemical or hormone-type sprays is during flowering before fruit set, usually from flower buds to the full bloom stage. It is imperative that you spray at this time for chemicals to be most effective on the flower bud. Spraying before or after flowers results in wasted time and money. Temperature. Hormone-type sprays are influenced by weather conditions. Daytime temperatures at the time of application should be between 60 degree F and 95 degree F for best results. Use correct concentrations. A concentration too low can increase fruit set. Excess hormone applications will cause damage to the plant. Spray stress-free plants. Plants being treated should be healthy and vigorous. Spraying plants under stress can cause additional damage to a plant. The chemical ethephon, used to stop fruiting, breaks down into a natural plant hormone, ethylene. Plants under stress from drought, high temperatures, insect and disease problems, or environmental stress, such as compacted soils, poor drainage, or improper pH will produce ethylene. Too much ethylene can be harmful to plants, causing injury symptoms such as leaf scorch, stem damage, or defoliation, further weakening the condition of the plant. AVAILABLE CHEMICALS Chemicals are available to reduce or eliminate fruit set on ornamental trees and shrubs. Check with local nurseries and garden centers — spraying cannot guarantee 100% effectiveness. Follow specific label directions for application rates and safety information. •Florel® Fruit Eliminator by Monteray, active ingredient: ethephon •Fruitone or App-L-Set, active ingredient: Naphthalene acid (NAA) •Carbaryl (trade name Sevin) — this insecticide is harmful to bees