Horticulture Tips for September

Home Grown  by Keith Reed
Before we talk about the usual landscaping tasks for September, reports coming in from eastern Oklahoma suggest we should talk about the possibility of high fall armyworm numbers. If this comes to pass, you can expect to see/hear quite a bit them from the news. A heavy armyworm outbreak tends to make for a good visual news story (from a ratings perspective) and can really grab people’s attention. If you’ve never seen an outbreak, it can be quite a sight as the caterpillars crawl across the ground by the thousands.

If your livelihood depends on maximum production of a grass plant such as wheat or turfgrass, then absolutely armyworms are a concern and their activity should be monitored carefully so control measure can be quickly initiated if armyworms do attack. However, if you are concerned about your home landscape, the situation is not as dire as it may appear.

As already mentioned, armyworms prefer grasses over other plants. While it is true they can effectively eat a lawn overnight, they only eat the leaf tissue, not the growing crown of the plant. In other words, they leave behind a lawn that looks terrible in the short term, but one that will recover with no lasting impacts. An exception would be a recently seeded lawn where the plants are not yet mature.

Other landscape tasks to consider for this month:
  • September and early October is the best time us to establish (or refresh) cool season lawns. See OSU Fact Sheet #HLA-6419 Establishing a Lawn in Oklahoma (PDF/Mobile).
  • September is the month to resume nitrogen fertilization for shade loving lawns such as tall fescue. Conversely, mid-month should be the last nitrogen fertilization for warm season turfgrasses such as bermuda or zoysiagrass. See #HLA-6420 Lawn Management in Oklahoma.
  • Now is the time to plant fall-flowering color plants such as pansies, kale, mums, and snapdragons.
  • September on into fall is the best time of year to plant most woody trees and shrubs.
  • Homeowners with mature landscapes are no stranger to surprise tree seedlings popping up, especially in perennial beds. For the most part, these are simply weeds. However, desirable trees can also pop up. Eastern redbuds are a great example. September is a good time to flag these seedlings for eventual transplanting later this winter when they are dormant.

For more information on 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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