Monthly Gardening Tips

September Tips

Oklahoma Cooperative Extension Service, Division of Agricultural Sciences and Natural Resources

Department of Horticulture & Landscape Architecture, Oklahoma State University

David Hillock, Consumer Horticulturist

Landscape

  • Watch for fall specials at garden centers and nurseries since fall is a great time for planting many ornamentals.
  • Choose spring flowering bulbs as soon as available.
  • Plant cool-season annuals like pansies, ornamental cabbage or kale, snapdragons and dusty miller when temperatures begin to cool.
  • Watch for and control any late infestations of tree webworms.
  • Twig girdler insects should be controlled if large numbers of small branches of elms, pecans, or persimmons are uniformly girdled from the tree and fall to the ground.
  • Begin to reduce the amount of light on outside tropical houseplants by placing them under shade trees before bringing them indoors for the winter.

Vegetables

  • You have all of September to plant cool-season vegetables like spinach, leaf lettuce, mustard and radishes, and until the middle of September to plant rutabagas, Swiss chard, garlic and turnips.

Lawn

  • Last nitrogen fertilizer application of the year on warm-season grasses should be applied no later than September 15th. (HLA-6420)
  • Winter broadleaf weeds like dandelion will begin to emerge in late September, which is also the best time to control them with a 2, 4-D type herbicide.
  • If pre-emergent control of winter-annual weeds (henbit, chickweed, annual bluegrass, etc.) is desired in lawns, the application should be completed by the 2nd week of September. (HLA-6421) Note: Do not treat areas that will be seeded in the fall.
  • Continue bermudagrass spray program with glyphosate products for areas being converted over to tall fescue this fall. (HLA-6421)
  • Plan to seed bluegrass, fescue or ryegrass as needed in shady areas in mid- to late-September. Fall is the best time to establish cool-season lawns (HLA-6419).
  • White grub damage can become visible this month. Apply appropriate soil insecticide if white grubs are a problem (EPP-7306). Water product into soil.

Building Healthy Soils

By David Hatlock, OSU, Senior Extension Specialist

Gardeners want a healthy soil in which to grow plants. This includes ample organic matter, good drainage, sufficient water holding capacity, a rich supply of nutrients and active biological life. Unfortunately, healthy soils are commonly removed from building sites during construction, leaving a new home sitting atop sub-soils, which are often compacted and devoid of nutrients.

Before you can build a healthy soil, you need to know what you have to work with. Soil tests are a great way to determine soil pH, nutrient contents and organic matter content. Simply feeling the soil, running it through your fingers is a good way to identify the texture of your soil. Sandy soils feel gritty and clods break apart very easily. Clay soils are sticky and clods are very hard. A clay soil can be molded in your hands.  Loam soils, the ideal condition for gardening, feel smooth in your hand. They are easy to work.

Surface and sub-soil types vary significantly across the state. If you live near a river you may have a very sandy soil, while other areas have heavy clays. Fortunately, the secret to improving soil is the same for both conditions. And that secret is organic matter. Organic matter is a term used to describe living and dead materials derived from plants or animals including compost, manure, straw, leaves, grass clippings or kitchen scraps. Organic matter enriches soil by providing a surface area where water and nutrients can bind. In clay soils, organic matter loosens structure to improve drainage. Organic matter also invites beneficial organisms into the soil. Soils rich in organic matter are going to have a darker color and many more nutrients.

 

Fall is a great time of year to add organic matter to the garden. It will decompose over the winter months to build healthier soils.

References: HLA-6436 – Healthy Garden Soils

PSS-2257 – Building Soil Organic Matter for a Sustainable Organic Crop Production