# Lawn care calendar for Oregon: when to fertilize and seed

> Oregon lawn calendar: feed on four holidays, seed mid-August to mid-September, west and east of the Cascades, with NOAA frost dates for Portland and Redmond.

Canonical: https://lucernel.com/guides/lawn-care-calendar/oregon
Last updated: 2026-10-30

Oregon lawns follow two different calendars split by the Cascades. West of them, perennial ryegrass and fine fescue grow almost year-round and rest through a dry summer. East of them, Kentucky bluegrass mixes need irrigation and sleep under snow. Oregon State University Extension publishes both, with the same late-summer window for seed.

**Seed Oregon lawns from mid-August to mid-September and feed four times a year.** Oregon State University Extension calls mid-August to mid-September almost perfect for seeding, with early May to mid-June a workable second choice, and sod from mid-March to mid-November in western Oregon. For feeding, its specialist suggests four applications a year: Memorial Day, Fourth of July, Labor Day and Thanksgiving, using a fertilizer high in nitrogen with little or no phosphorus. (Oregon State University Extension)

| Month | Western Oregon | Central and Eastern Oregon |
| --- | --- | --- |
| January | Mow only when needed | Dormant under snow; no mowing or water |
| February | Mow lightly if growing | Dormant; no mowing or water |
| March | Sod season opens mid-March; mow as the grass grows | Growth starts slowly; 0 to 2 mowings |
| April | Mow weekly in spring; aerate and lime if the soil test calls for it | About 4 mowings; 0 to 3 inches of water; dethatch April to early June |
| May | First feeding around Memorial Day; seeding is workable until mid-June | High-rate lawns feed in May; 4 to 6 mowings; 3 to 5 inches of water |
| June | Mow less often as summer dryness arrives | 4 to 6 inches of water; second feeding June to early July for high-rate lawns |
| July | Second feeding around the Fourth of July; dormancy is acceptable | 5 to 7 inches of water; 4 mowings |
| August | Mid-August opens the best seeding window | 4 to 6 inches of water; 4 mowings |
| September | Feed around Labor Day; seed through mid-September | Optional feeding September to October; 3 to 4 inches of water; dethatch in fall |
| October | Mow weekly in fall; renovate thin lawns | 2 or 3 mowings; 1 to 3 inches of water |
| November | Feed around Thanksgiving; sod season ends mid-November | Late fall feeding mid-November to early December; shut off water |
| December | Mow only when needed | Dormant |

Western Oregon follows the OSU specialist's fertilizing holidays and the lawn establishment guide; Central and Eastern Oregon follows OSU's Central Oregon maintenance calendar, whose water and mowing figures are monthly totals.

## Which grasses grow where in Oregon

OSU Extension names perennial ryegrass as the best lawn grass for western Oregon, where winters are cool and wet, and Kentucky bluegrass for central and eastern Oregon. Tall fescue works in both. A mix of perennial ryegrass and fine fescue suits sunny sites west of the Cascades, a fescue-heavy mix with a little ryegrass suits shade, and a blend of Kentucky bluegrass and perennial ryegrass is the pick east of them. Plain Kentucky bluegrass seed alone is not recommended, because weeds sprout faster than the grass.

Perennial ryegrass can be hurt by cold in central and eastern Oregon. In western Oregon, tall fescue goes semidormant in winter and is prone to leaf spot and Microdochium patch, especially in its first winter, while Kentucky bluegrass catches cool-weather diseases and does not persist. All three lawns can go dormant west of the Cascades in summer without irrigation, if you accept brown grass and drought-tolerant weeds, but east of them irrigation is needed to keep a lawn alive.

## Frost dates from NOAA

Dates are the NOAA 1991-2020 normals for the last spring and first fall 32 F freeze at 50% probability. At Portland International Airport the last spring frost averages March 13 and the first fall frost November 19. At Eugene they are April 11 and October 23, at Medford April 8 and October 29, and at Redmond (Roberts Field) June 9 and September 14.

Counting the days between them gives about 251 frost-free days at Portland and 97 at Redmond (our arithmetic). Central Oregon lawns have a frost-free window of about three months where Portland lawns have eight.

## Spring

West of the Cascades, mow weekly in spring and fall and less often in summer and winter, never removing more than a third of the height, and leave the clippings unless they clump. OSU asks for a taller cut than most people use: around 2 inches is typical, and its specialist says taller is better, because a one-inch cut reduces root depth and means more water.

Soil pH of 6.0 to 6.5 is the target, and most western Oregon lawns benefit from lime every two to three years when pH is below 6.0. East of the Cascades, OSU's central Oregon calendar has growth rising from low in March to medium in April and high from May, with four mowings in April and four to six in May and June, at 1.5 to 2.5 inches for ryegrass, fine fescue or bluegrass. Dethatching is best in April to early June or in September and October.

## Summer

Watering guidance is a total of about 1 inch a week in small doses, since most roots sit in the top inch of soil and OSU says more than a quarter inch at a time can be wasted on a shallow-rooted lawn. In central and eastern Oregon, the monthly irrigation estimates run 3 to 5 inches in May, 4 to 6 in June, 5 to 7 in July and 4 to 6 in August, applied one to three times a week.

West of the Cascades, dormancy is a choice. A lawn that goes brown in July and August usually greens back up when fall rains arrive, and OSU treats it as a water-saving practice, with the warning that unirrigated lawns are open to weeds and compaction from summer foot traffic.

## Fall

Mid-August to mid-September is the best seeding window, since days are warm, nights cooler and the day length is falling, and OSU says you can expect to see green grass within a week and a first mowing about three weeks after seeding. Early May to mid-June is the second choice. Sod follows the same preference, but can be laid from mid-March to mid-November in western Oregon all year on the coast, and from about April through October in much of central and eastern Oregon with irrigation.

OSU recommends renovating a lawn in fall before replacing it: test the soil, aerate bare and compacted spots, lime if needed, fertilize, overseed and water lightly every day until the seed germinates, topping with no more than a quarter inch of compost or sawdust. The fertilizer it names is high in nitrogen with low or no phosphorus and a medium potassium level, for example 20-2-6.

## Fertilizer rules

OSU's specialist suggests four feedings a year for western Oregon: Memorial Day, the Fourth of July, Labor Day and Thanksgiving. The central Oregon calendar gives three rate levels. High-rate lawns feed in May, June to early July and mid-November to early December; medium-rate lawns feed mid-May to early June and in November or December; low-rate lawns feed only in November or December, with optional low-rate feedings in May and June and a September to October feeding. Each is 1 pound of nitrogen per 1,000 square feet, and late fall feedings may be doubled.

I found no Oregon rule limiting phosphorus in home lawn fertilizer; the state code chapter I opened, ORS 633, deals with grades, standards and labels for feeds, soil enhancers and seeds. The lawn fertilizer calculator on this site converts a bag's nitrogen percentage into pounds of product for your lawn size and the 1 pound target.

## Frequently asked questions

### When should I fertilize my lawn in Oregon?

OSU's lawn specialist suggests Memorial Day, the Fourth of July, Labor Day and Thanksgiving for western Oregon. The Central Oregon calendar uses May, June to early July and mid-November to early December for a high-rate lawn.

### When is the best time to seed grass in Oregon?

Mid-August to mid-September, according to OSU Extension. Early May to mid-June is the second-best window. Sod can be laid from mid-March to mid-November in western Oregon.

### What grass should I plant in Oregon?

A mix of perennial ryegrass and fine fescue west of the Cascades, with more fine fescue in shade, and Kentucky bluegrass with perennial ryegrass in central and eastern Oregon, according to OSU Extension.

### Should I water my lawn in an Oregon summer?

West of the Cascades it is optional. All the common lawn grasses survive dormancy without irrigation if you can accept brown grass and drought-tolerant weeds. In central and eastern Oregon, a lawn needs irrigation to persist.

### Can Lawnzo help me follow an Oregon lawn schedule?

Lawnzo for iPhone plans each lawn from its grass, sun and irrigation, and tests mowing, seeding and feeding days against the forecast. If your Labor Day feeding gets pushed by rain, it tells you the reason.

## Sources (checked 2026-10-02)

- [OSU Extension, Lawn maintenance calendar for Central Oregon](https://extension.oregonstate.edu/gardening/lawn/lawn-maintenance-calendar-central-oregon)
- [OSU Extension, Bring your lawn back to life this fall with renovation and care](https://extension.oregonstate.edu/news/bring-your-lawn-back-life-fall-renovation-care)
- [OSU Extension, Choose the right grass for your Oregon lawn](https://extension.oregonstate.edu/news/choose-right-grass-your-oregon-lawn)
- [OSU Extension, Irrigation rates and frequencies for Western and Eastern Oregon turfgrass (EM 9311)](https://extension.oregonstate.edu/catalog/em-9311-irrigation-rates-frequencies-western-eastern-oregon-turfgrass)
- [OSU Extension, Practical lawn establishment and renovation (EC 1550)](https://extension.oregonstate.edu/catalog/pub/ec-1550-practical-lawn-establishment-renovation)
- [Oregon Revised Statutes, Chapter 633](https://oregon.public.law/statutes/ors_chapter_633)
- [NOAA NCEI 1991-2020 normals: frost dates for Portland, Eugene, Medford and Redmond (API query)](https://www.ncei.noaa.gov/access/services/data/v1?dataset=normals-annualseasonal-1991-2020&stations=USW00024229,USW00024221,USW00024225,USW00024230&dataTypes=ANN-TMIN-PRBLST-T32FP50,ANN-TMIN-PRBFST-T32FP50&format=json)
- [NOAA NCEI, U.S. Climate Normals 1991-2020 (product page)](https://www.ncei.noaa.gov/products/land-based-station/us-climate-normals)