Horticulture Tips for May

Home Grown  by Keith Reed
The best time to prune most spring flowering shrubs is right after they have dropped their blooms. These plants flower from buds set last year, so pruning now (as needed to control growth or improve shape) insures that the plant has plenty of time to re-grow and set buds fully for the following year. The forsythia is a great example of this principal. These landscape standbys can tend to get large and unruly late in the summer and we have a tendency to want to prune them back at that time. The plant tolerates this just fine but it will not bloom the following spring.

Early to mid May should be the last time your tall fescue or other cool season lawn is fertilized until fall. Summer fertilization will only exacerbate disease and heat stress issues these grasses will soon face. On the other hand, now is the perfect time to make your first fertilizer application on your warm season turfgrasses such as bermuda and zoysia.

As we talked about last week, guessing at what nutrients your landscape might need or making an application just because that’s what I’ve always done can be a waste of money as well as being environmentally irresponsible. We would encourage you to use this as an incentive to have your soil tested if you have not done so in a few years. Contact us in the Extension office for more information on this service.

Bagworms are a common pest that typically affects our landscape plants beginning in late May. As early as other insects have appeared this season, I would suggest scouting for these insects soon. Look for small worms near the bags or on the tips of leaves. Control is much more effective if you begin treatments now while the insects are small. You can find more information on
OSU Fact Sheet EPP-7306 concerning scouting and control strategies for this pest. Remember that seeing only a few of a particular pest does not mean chemical control is warranted.

With our recent rains and forecast warm temperatures, you can expect to see fungal diseases becoming an issue. If you are spraying fruit trees, remain diligent in the timing of your applications during this period. If you are considering planting new roses, proceed with caution. In general, look for landscape roses as opposed to hybrid teas. These plants have been bred with disease resistance in mind and are much easier to maintain in the home landscape.

However, it is important to note that it is becoming clearer that all roses grown in Oklahoma are susceptible to rose rosette disease. If you grow roses, don’t panic, but it would be a good idea to take a look at
OSU Fact Sheet #EPP-7329 Rose Rosette Disease. This document provides some very helpful information on managing the disease and well as limiting it’s spread. This disease was also discussed in an earlier Home Grown article.

For more information of this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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