Saturday, March 11, 2017 By: Ask A Master Gardener

Hows and Whens to Fertilize Lawns

Tips for how and when to fertilize Oklahoma lawns

Bill Sevier: Master Gardener | Posted:

March 11, 2017

Q: When and how often should I fertilize my lawn? A.K., Tulsa

A:One should fertilize lawns during their growing seasons, which are different from one grass species to another. How often to fertilize depends on the quality of lawn desired and how often you are willing to mow it. Information about lawn care, including fertilization, is available in condensed form in the “Bermuda Maintenance and Fescue Maintenance documents” on the Master Gardener web site.

It sometimes is frustrating to try to understand what to do, when to do it and with what, when it comes to lawn care. Each type of grass should receive fertilizer only during its active growing season — warm season grasses grow in summer, cool season ones in spring and fall.
We live in a transition zone between where warm-season and cool-season turf grasses grow best and often our lawns have both types; usually a mix of Bermuda and fescue. The recommendations for each type are quite different, so a plan is important.
Warm-season grasses — Bermuda, zoysia and buffalo grass — prefer hot weather and actively grow in summer, April into September. They become dormant (turn brown) in winter; any brown grass in winter is one of these types of grasses.
Tall fescue and Kentucky bluegrass are cool-season grasses that grow best in spring and fall. They stop growing but remain green all winter. These grasses do not tolerate summer’s heat and must be irrigated.
Fertilize warm-season lawns from green-up in April to the first of September. Apply 2 to 5 pounds of actual nitrogen fertilizer per 1,000 square feet, in divided doses, during this time. Zoysia lawns need about half as much and buffalo grass about a third the amount of the Bermuda recommendation. If warm-season grasses are fertilized after early September, dormancy may be delayed causing them to be susceptible to winter kill and diseases.
Tall fescue and Kentucky bluegrass are often found growing together and benefit from each other’s strengths. Cool-season grasses should be fertilized during their active growing periods. Apply 1 pound of nitrogen fertilizer per 1,000 square feet in March or May and again in September and November. The fall applications are the most important. Never fertilize fescue in summer; it will make the grass susceptible to heat damage and disease.
The type of fertilizer is important. It is always best to base the type of fertilizer on the results of a soil test. In the absence of a soil test, and if you have fertilized the lawn in previous seasons, you need a fertilizer containing only nitrogen (nitrogen is the first number on a fertilizer bag). Soil test results in our area show adequate, or more often, excessive amounts of phosphorus and potassium and adding more may be harmful.
Fertilizers also come as immediately released and slow released versions. With the slow release types one can apply double the amount (2 pounds per 1,000 square feet) half as often than what is recommended.
Check out the Master Gardener website,, for more information.
For more information, contact the Master Gardeners at 918-746-3701 from 9 a.m. to 4 p.m.

Garden tips
Remove flowers from spring blooming bulbs after blooming is completed. This will allow the plant to direct its energy into its bulb for next year's blooms, rather than producing seeds.

Allow foliage of these bulb plants to die and turn brown naturally before removal. As long as the leaves are green, they are storing energy for the following year.

These bulb's root systems become inactive after blooming and cannot absorb fertilizer. It is best to fertilize them when planting or in the fall or in the spring when their leaves first emerge


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