Lawn maintenance calendar for Central Oregon

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Proper timing of cultural practices is an important part of having a nice lawn. Performing critical maintenance tasks at the wrong time generally yields poor results and wasted effort. This calendar is offered as a general guide to optimum times for common cultural practices.

Turf growth rate

Month Average high temp F Growth rate
January 38 None
February 45 None
March 51 Low
April 60 Medium
May 69 High
June 77 High
July 87 High
August 85 High
September 77 High
October 64 Medium
November 48 Low
December 40 None

Weather varies greatly in Eastern Oregon and the data shown roughly approximates climatic conditions typical in much of Central Oregon. The chart above depicts the growth patterns of turf during an average year. Turf is dormant during winter and, under unirrigated conditions, most grasses will not survive more than one year.


Number of mowings per month:

  • January: 0 mowings
  • February: 0 mowings
  • March: 0–2 mowings
  • April: 4 mowings
  • May: 4–6 mowings
  • June: 4–6 mowings
  • July: 4 mowings
  • August: 4 mowings
  • September: 4 mowings
  • October: 2–3 mowings
  • November: 0 mowings
  • December: 0 mowings

Mowing has a greater influence on the year-round quality of turf than any other practice. Proper cutting height varies for turfgrass species. Lawns composed primarily of perennial ryegrass, fine fescues or Kentucky bluegrass do well when mowed at a height of 1.5 to 2.5 inches.

Weekly mowing is adequate to produce good quality turf during the greater part of the year. If you can't manage to mow regularly, don't expect to maintain top-quality turf. Frequent mowing at the proper height requires less time and effort than infrequent mowing and results in a healthy, dense, vigorous turf with fewer maintenance problems.

Fertilizer — application timing

  • High fertilizer rate:
    • May
    • June–early July
    • Mid-November–early December
  • Medium fertilize rate:
    • Mid-May–early June
    • November–December
  • Low fertilizer rate
    • November–December
  • Optional fertilizer:
    • May–June (low rate)
    • September–October (high or medium rate)

Fertilizer is a tool that can help you maintain quality, weed-free turf year-round. Since expectations vary, program for three different levels of culture are outlined. All applications are at a rate of 1 lb. nitrogen per 1,000 sq. ft. except late fall applications which may be doubled. This rate is adequate assuming you are using soluble or mixed soluble, slow-release nitrogen fertilizers. (Depending on soil test value, you may choose to use straight nitrogen materials such as ammonium sulfate or complete fertilizers containing N-P-K. Optimum ratios for N-P-K materials range from 3-1-2 to 6-1-4.)


Optimum timing for dethatching is early spring (April, May or the first part of June) just as the turf growth rate is increasing, or in the fall months of September or October when temperatures begin to moderate. Many problems are attributed to excess thatch.

When thatch buildup is heavy, most roots are in the thatch layer and not in the soil. When this happens, drought tolerance decreases because the roots draw moisture from a smaller reservoir. You have to irrigate more often and will find it harder to have a uniformly nice lawn.

Mechanical dethatching is still the best solution to thatch control. Dethatching should be followed by a nitrogen fertilizer application to stimulate rapid recovery. In areas where annual grasses are a problem, spring dethatching should be followed by an application of an appropriate herbicide in addition to fertilizer.


  • January: 0 inches of water/month
  • February: 0 inches of water/month
  • March: 0 inches of water/month
  • April: 0–3 inches of water/month
  • May: 3–5 inches of water/month
  • June: 4–6 inches of water/month
  • July: 5–7 inches of water/month
  • August: 4–6 inches of water/month
  • September: 3–4 inches of water/month
  • October: 1–3 inches of water/month
  • November: 0 inches of water/month
  • December: 0 inches of water/month

The main questions in turf irrigation are how much and how often. Frequency is largely a matter of preference. For most of the irrigation seasons, lawns will need to be irrigated from one to three times per week if you want an attractive lawn. Perhaps the best way to gauge frequency is to watch the lawn. If you are irrigating once per week and the lawn is turning brown between waterings, you should irrigate more often. If you are irrigating every night and the lawn is mushy and wet, you can reduce the frequency. How much water to put on can be estimated by calculated evapotranspiration numbers.

Evapotranspiration (ET) is a fancy term describing the amount of water used by the turf. ET can be calculated from evaporation data accumulated at weather stations. Monthly ET estimates for several areas in Central and Eastern Oregon are listed below. The values represent water used by turf on a per-month basis. For example, in Klamath Falls you can anticipate turf will need 6 inches of water in June. On a per-week basis, it needs 1.5 inches. You might choose to irrigate once per week at 1.5 inches of water or three times per week at 0.5 inches of water. ET values provide a good reference point for planning your irrigation strategy.

Estimated ET (inches)
Month K Falls Madras Malheur Br Pendleton Union
January 0 0 0 0 0
February 0 0 0 0 0
March 0 0 0 2.4 0
April 3.2 0 3.7 3.4 2.1
May 5.0 5.0 4.9 4.7 3.1
June 6.0 6.0 5.8 5.9 4.1
July 7.2 7.2 7.4 7.7 5.0
August 6.6 6.2 6.3 6.9 4.4
September 4.1 4.2 4.0 4.2 2.7
October 2.8 2.6 1.9 2.3 1.6
November 0 0 0 0 0
December 0 0 0 0 0

Establishment and renovation

The best time for seeding is generally mid-August through mid-September. Spring seeding may be done but requires more care after planting and may be invaded by weedy summer annual grasses. Sod can be planted anytime from late April to mid-October. Midsummer plantings require careful irrigation due to hot, dry conditions. For details on establishing lawns in Eastern Oregon, refer to EC 1550, Practical Lawn Establishment and Renovation.

Renovation involves reseeding a lawn without removing the existing sod or rototilling the soil. This is often done after severe dethatching or after the original turf has been killed with a chemical spray. Renovation is most successful in the fall but may also be done in May.

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