Montana Lawn Care Calendar 2026: Fall & Spring Task Dates

Q: When should I overseed my lawn in Montana?

Overseed Montana cool-season lawns August 3 to August 25, roughly 7 to 4 weeks before the typical first frost (September 22), while soil is still above 50°F and seedlings get 6+ weeks before a hard freeze. Seed-to-soil contact matters more than the exact date: mow low, rake or core-aerate first.

Q: When should I fertilize my lawn in the fall in Montana?

Feed Montana cool-season lawns August 25 to September 15, about 4 to 1 weeks before the typical first frost. Fall nitrogen builds roots and next spring's green-up; many extension programs add a second, lighter feed around the final mow. Use a soil test for phosphorus and potassium, because several states restrict phosphorus in lawn fertilizer.

Q: When do you plant garlic in Montana?

Plant garlic in Montana September 8 to October 13, around the typical first frost (September 22), so cloves root for 4 to 6 weeks before the ground freezes without sending up much top growth. Hardneck varieties (Music, German Extra Hardy, Chesnok Red) are the reliable choice; mulch with 4 to 6 inches of straw after planting.

Q: When should I aerate my lawn in Montana?

Core-aerate Montana cool-season lawns August 3 to September 1, in early fall while the grass is growing actively, and pair it with overseeding and the fall feed. Use a plug aerator on moist (not wet) soil and leave the cores to break down.

Q: When should I winterize my sprinklers in Montana?

Winterize Montana irrigation September 17 to October 6, before the first HARD freeze (28°F), which usually follows the first frost (September 22) by one to three weeks. Shut the supply, blow out every zone at 50 to 80 psi, open the backflow test cocks, and switch the controller off.

Q: When should I apply pre-emergent in Montana?

Spring pre-emergent for crabgrass goes down as soil at 1 to 2 inches approaches 55°F, typically April 29 to May 27 in Montana. A fall application for annual bluegrass, henbit, and chickweed lands July 24 to August 23, as soil cools through 70°F. Check the live soil temperature on this page before the calendar.

Q: When is the last time to mow in Montana?

Plan the final mow September 15 to October 6, and keep cutting as long as the grass grows, then take the last cut to about 2 to 2.5 inches for cool-season turf. Left long, grass mats under snow and invites snow mold.

Q: What kind of grass grows best in Montana?

Montana is a cool-season state. The common lawn grasses are Kentucky bluegrass, fine fescues, perennial ryegrass. Montana lawns are nearly all bluegrass and fescue — MSU Extension's fall checklist front-loads everything into August because Great Falls and Bozeman can frost by mid-September.

Every lawn and garden task dated to Montana's frost calendar and live soil temperature: cool-season grasses, extension-service timing.

Next up in Montana: plant garlic, window open through October 13

Grass zone

Cool-season

Overseed

Aug 3 to Aug 25

First frost

Sep 22

The Montana fall lawn season at a glance

Live · soil temp updates hourly

Today

Montana's overseeding window against the fall season. Windows are frost-date typicals; any year moves ±2 weeks.

Cool-season

grass zone

Kentucky bluegrass

September 22

typical first frost

passed this year

Plant garlic

next task

window open now

No reading

soil now · Billings

live data unavailable

Montana lawns are nearly all bluegrass and fescue — MSU Extension's fall checklist front-loads everything into August because Great Falls and Bozeman can frost by mid-September.

Live · this week

What to do in Montana right now

Tasks whose window is open or opening within three weeks, checked against live soil temperature at Billings (live reading unavailable, calendar only). Enter your ZIP for your own soil reading.

Plant garlic

Do it now

September 8 – October 13

Inside the typical window (September 8 – October 13).

How to plant garlic

Plant tulips & bulbs

Do it now

September 15 – October 27

Inside the typical window (September 15 – October 27).

How to plant tulips & bulbs

Covers all 50 states. Windows are frost-date typicals; live soil temperature adjusts the soil-gated tasks.

The full calendar

Montana fall lawn & garden calendar

Task	Typical window	Status	Why now
Fall pre-emergent	July 24 to August 23	Done for the year	Stops winter annual weeds — annual bluegrass (Poa annua), henbit, chickweed — from germinating as soil cools through 70°F.
Bring houseplants in	September 1 to September 19	Done for the year	Tropical houseplants are damaged by nights in the 40s, well before any frost — and a sudden move from 50°F nights to a 70°F house causes leaf drop.
Core aerate	August 3 to September 1	Done for the year	Relieves compaction and opens thatch so water, air, and fertilizer reach the roots — and it is the best seedbed prep for overseeding.
Overseed	August 3 to August 25	Done for the year	Warm soil plus cool air is the best germination combination of the year, and new seedlings need 6–8 weeks of growth before the first hard freeze.
Cover crop / winter rye	August 11 to September 8	Done for the year	A cover crop holds soil, scavenges leftover nitrogen, and adds organic matter over winter — bare vegetable beds lose both soil and fertility to winter rain.
Fall fertilizer	August 25 to September 15	Done for the year	Fall nitrogen builds roots and carbohydrate reserves instead of top growth — the single most valuable feeding of the year for cool-season turf.
Plant garlic	September 8 to October 13	Do it now	Garlic needs 4–6 weeks to root before the ground freezes but should not push much top growth — planting around the first frost, 2 weeks either side, is the sweet spot.
Final mow	September 15 to October 6	Done for the year	Grass left long under snow mats and invites snow mold; cut too short it loses winter insulation. The last cut at 2–2.5 inches is the compromise.
Winterize sprinklers	September 17 to October 6	Done for the year	Water left in lines and backflow preventers expands when it freezes and splits pipes, valves, and heads — a repair that costs more than the whole winterization.
Plant tulips & bulbs	September 15 to October 27	Do it now	Bulbs root in cool soil and need 12–14 weeks of chilling below 45°F to flower — planted into warm soil they rot or sprout early.

Lawn with fallen leaves, half of them shredded by a mulching mower — Mulch the leaves into the lawn on the last mows: shredded leaves feed the soil, while a matted layer smothers the grass. “2023-11-02 11 25 12 A lawn with fallen leaves where half have been shredded by a mulching mower along Aquetong Lane in the Mountainview section of Ewing Township, Mercer County, New Jersey” by Famartin, CC BY-SA 4.0

Looking ahead

Montana spring lawn calendar

Spring runs off the last frost (May 20) and, for pre-emergent, off soil temperature. The crabgrass trigger is 55°F at 1 to 2 inches for four or five days, not a date.

Task	Typical window	Why then
Spring pre-emergent	April 29 to May 27	Crabgrass germinates when soil at 1–2 inches holds 55°F for 4–5 consecutive days. Pre-emergent has to be in place BEFORE that — it has no effect on crabgrass that has already sprouted.
First mow	May 6 to May 27	The first cut removes winter-damaged tips and signals the lawn to tiller and thicken — but mowing soggy soil ruts it, and scalping stresses turf before roots are working.
Spring grass seed	May 13 to June 17	Spring seeding is second-best (fall is better) because seedlings face summer heat and crabgrass, but it is the only window for warm-season seed, which needs 65–70°F soil.
First spring fertilizer	June 3 to July 1	Feeding too early pushes leaf growth ahead of root growth and feeds weeds — wait until the lawn is actively growing and has been mowed 2–3 times (cool-season) or is fully green (warm-season).

City by city

Soil temperature and frost countdown across Montana

City	Soil temp now (6 cm)	Typical first frost	Days to first frost	Typical last frost
Billings	loading…	September 30	passed	May 10
Missoula	loading…	September 22	passed	May 20
Bozeman	loading…	September 14	passed	May 26

Soil temperature is modeled at 6 cm by Open-Meteo and read live in your browser; frost dates are NOAA 1991 to 2020 normals for each reference station.

What grows here

Montana lawn grasses and mowing heights

Montana is a cool-season state. Common lawn grasses: Kentucky bluegrass, fine fescues, perennial ryegrass. Cool-season grasses grow hardest in spring and fall, go semi-dormant in summer heat, and are seeded and fed in fall.

Grass	Mowing height
Kentucky bluegrass	2.5 to 3.5 in
Tall fescue	3 to 4 in
Perennial ryegrass	2.5 to 3 in
Fine fescues	2.5 to 3.5 in

Bermudagrass lawn overseeded with perennial ryegrass — Bermudagrass overseeded with perennial ryegrass: the warm-season answer to a green winter lawn. “Bermudagrass couch overseeded with Homerun perennial ryegrass” by Gilba Solutions Pty Ltd, CC BY-SA 4.0

How to do each one

Task-by-task guide for Montana

Fall pre-emergent · July 24 to August 23

Why: Stops winter annual weeds — annual bluegrass (Poa annua), henbit, chickweed — from germinating as soil cools through 70°F.

How: Apply prodiamine or dithiopyr at the label rate when soil at 2–4 inches drops toward 70°F for several days, then water in ½ inch. Skip it on any lawn you plan to seed this fall — pre-emergent blocks grass seed too.

Rule: Cool-season: 60–30 days before first frost. Warm-season: 75–45 days before first frost. · full guide →

Bring houseplants in · September 1 to September 19

Why: Tropical houseplants are damaged by nights in the 40s, well before any frost — and a sudden move from 50°F nights to a 70°F house causes leaf drop.

How: Start when night lows dip below 50°F. Inspect and rinse foliage, treat for pests (insecticidal soap, and a soil drench or repot for fungus gnats), then move plants to a bright window over a week, starting with a few nights indoors. Cut watering back by half once inside.

Rule: 3 weeks before first frost until a few days before (when nights fall below 50°F).

Core aerate · August 3 to September 1

Why: Relieves compaction and opens thatch so water, air, and fertilizer reach the roots — and it is the best seedbed prep for overseeding.

How: Use a core (plug) aerator, not spikes, on moist soil — two passes at right angles, 20–40 holes per square foot. Leave the plugs to break down. Cool-season lawns: early fall during active growth. Warm-season lawns: late spring to early summer when bermuda and zoysia are growing hardest.

Rule: Cool-season: 7–3 weeks before first frost. Warm-season: 8–15 weeks after last spring frost. · full guide →

Overseed · August 3 to August 25

Why: Warm soil plus cool air is the best germination combination of the year, and new seedlings need 6–8 weeks of growth before the first hard freeze.

How: Mow low, rake or dethatch so seed touches soil, core-aerate if you can, then spread seed (tall fescue 6 lb, bluegrass 2–3 lb, perennial rye 6–8 lb per 1,000 sq ft). Water lightly twice a day for two weeks. Warm-season lawns only overseed with annual/perennial ryegrass for winter color.

Rule: Cool-season: 7–4 weeks before first frost. Warm-season (ryegrass): 6–3 weeks before first frost. · full guide →

Cover crop / winter rye · August 11 to September 8

Why: A cover crop holds soil, scavenges leftover nitrogen, and adds organic matter over winter — bare vegetable beds lose both soil and fertility to winter rain.

How: Broadcast cereal (winter) rye at 2–3 lb per 1,000 sq ft into cleared beds, rake in ¼–½ inch, and water. Rye germinates down to 34°F soil, so it is the last-chance cover crop; mix in crimson clover or hairy vetch if you have 4+ weeks before frost. Mow and turn under 3–4 weeks before spring planting.

Rule: 6–2 weeks before first frost (rye itself can go in right up to frost).

Fall fertilizer · August 25 to September 15

Why: Fall nitrogen builds roots and carbohydrate reserves instead of top growth — the single most valuable feeding of the year for cool-season turf.

How: Cool-season lawns: 0.75–1 lb of actual nitrogen per 1,000 sq ft, slow-release, with a soil test deciding phosphorus and potassium. Warm-season lawns take their LAST nitrogen on a calendar cutoff, not a frost countdown — mid-August across most of the South (Clemson: no nitrogen after August 15, coastal September 1; UGA: nitrogen through mid-August; LSU AgCenter: nothing after the end of August), and September in Florida and Texas. Late nitrogen on bermuda or centipede invites winterkill and large patch.

Rule: Cool-season: 4–1 weeks before first frost. Warm-season: last nitrogen of the year by mid-August to mid-September — an extension calendar cutoff, not a frost offset. · full guide →

Plant garlic · September 8 to October 13

Why: Garlic needs 4–6 weeks to root before the ground freezes but should not push much top growth — planting around the first frost, 2 weeks either side, is the sweet spot.

How: Break bulbs into cloves the day you plant. Set cloves pointy end up, 2 inches deep (3 in cold zones), 6 inches apart, in full sun and loose, compost-rich soil. Mulch 4–6 inches of straw in cold climates. Hardneck varieties (Music, German Extra Hardy, Chesnok Red) for the North; softnecks (Inchelium Red, California Early) for the South, where they need little or no chilling.

Rule: Cool/transition: 2 weeks before to 3 weeks after first frost (before the ground freezes). Warm South: 2 weeks before to 3 weeks after first frost. · full guide →

Final mow · September 15 to October 6

Why: Grass left long under snow mats and invites snow mold; cut too short it loses winter insulation. The last cut at 2–2.5 inches is the compromise.

How: Keep mowing as long as the grass grows (it slows sharply below 50°F). Drop the deck one notch on each of the last two mows so the final height is about 2–2.5 inches for cool-season turf. Mulch the last leaves into the lawn rather than bagging.

Rule: 1 week before to 2–3 weeks after first frost, when growth stops.

Winterize sprinklers · September 17 to October 6

Why: Water left in lines and backflow preventers expands when it freezes and splits pipes, valves, and heads — a repair that costs more than the whole winterization.

How: Shut the supply valve, drain or blow out each zone with compressed air (50–80 psi for poly pipe, never more), open the test cocks on the backflow preventer, and set the controller to "off" (not "rain delay"). Do it before the first HARD freeze (28°F), which typically follows the first frost by 1–3 weeks.

Rule: From just before first frost until first hard freeze (~2 weeks later).

Plant tulips & bulbs · September 15 to October 27

Why: Bulbs root in cool soil and need 12–14 weeks of chilling below 45°F to flower — planted into warm soil they rot or sprout early.

How: Plant when soil at 6 inches falls below 55°F: tulips and daffodils 6–8 inches deep, 4–6 inches apart, pointy end up, in well-drained soil. Water once, then leave them. Zones 8 and warmer: pre-chill tulips 10–12 weeks in the refrigerator (away from fruit) and plant in late November or December.

Rule: Cool/transition: 1 week before to 5 weeks after first frost. Warm South: 2–8 weeks after first frost with pre-chilled bulbs. · full guide →

Spring pre-emergent · April 29 to May 27

Why: Crabgrass germinates when soil at 1–2 inches holds 55°F for 4–5 consecutive days. Pre-emergent has to be in place BEFORE that — it has no effect on crabgrass that has already sprouted.

How: Watch soil temperature, not the calendar: apply prodiamine, dithiopyr, or pendimethalin as soil approaches 55°F (forsythia bloom is the old signal). Water in ½ inch within 48 hours. Dithiopyr also controls crabgrass up to about the 2-leaf stage if you run late. Do not apply where you will seed within 3–4 months.

Rule: Cool-season: 3 weeks before to 1 week after last spring frost. Transition: 4 weeks before to just before last frost. Warm-season: 5–1 weeks before last frost. · full guide →

First mow · May 6 to May 27

Why: The first cut removes winter-damaged tips and signals the lawn to tiller and thicken — but mowing soggy soil ruts it, and scalping stresses turf before roots are working.

How: Mow when grass reaches about 3 inches and the soil is firm underfoot, taking off no more than a third of the blade. Sharpen the blade first. Warm-season lawns: one low "scalp" mow at green-up removes dead top growth and speeds warming of the crowns — bag those clippings.

Rule: Cool-season: 2 weeks before to 1 week after last frost. Warm-season: 1 week before to 3 weeks after last frost.

Spring grass seed · May 13 to June 17

Why: Spring seeding is second-best (fall is better) because seedlings face summer heat and crabgrass, but it is the only window for warm-season seed, which needs 65–70°F soil.

How: Cool-season seed germinates from 50°F soil — seed as early as the ground can be worked and skip pre-emergent on that area (or use mesotrione, which is safe on new seedings). Warm-season seed (bermuda, zoysia, centipede, buffalograss) waits for 65°F+ soil, typically late spring. Keep the top ½ inch moist until established.

Rule: Cool-season: 1 week before to 4 weeks after last frost. Warm-season: 6–12 weeks after last frost.

First spring fertilizer · June 3 to July 1

Why: Feeding too early pushes leaf growth ahead of root growth and feeds weeds — wait until the lawn is actively growing and has been mowed 2–3 times (cool-season) or is fully green (warm-season).

How: Cool-season: a light feeding (0.5–0.75 lb N per 1,000 sq ft) in late spring; the heavy feeding belongs in fall. Warm-season: wait until bermuda, zoysia, or St. Augustine is 100% green, then 1 lb N per 1,000 sq ft; centipede gets half that, once. Never fertilize dormant warm-season turf.

Rule: Cool-season: 2–6 weeks after last frost. Warm-season: 6–10 weeks after last frost (full green-up).

Tow-behind plug aerator pulling soil cores from a lawn — Plug (core) aeration, not spikes; the cores left on the surface break down in a couple of weeks. “Plug Aerator” — Agri-Fab, Inc. — CC0

Why the dates are what they are

Soil temperature, growing degree days, and the frost anchor

Hand working loose soil in a raised bed — Soil lags air by weeks in both directions, which is why a calendar alone gets pre-emergent and bulbs wrong. “The Bundled Benefits of Soil Health 32” — USDA / Lance Cheung — Public domain

Soil temperature beats air temperature. Grass seed germinates from about 50°F soil, crabgrass from a sustained 55°F, warm-season seed from 65°F, and tulips want soil under 55°F so they root without sprouting. Soil at seed depth warms and cools far more slowly than the air above it, so a hot week in April or a cold snap in October moves the soil only a few degrees. That is why the soil-gated tasks on this page defer to the live reading over the calendar.

Growing degree days (GDD) are how turf scientists track it: daily heat accumulated above a base (usually 50°F). Crabgrass germination, for instance, lines up with roughly 200 GDD base 50°F in spring, the same signal as forsythia finishing bloom. The frost calendar is the long-run average of all that heat accounting.

Why first frost anchors the fall. Most fall tasks are really a countdown to the first hard freeze: seedlings need 6 to 8 weeks of growth before it, garlic needs 4 to 6 weeks of rooting, cool-season fertilizer needs 2 to 4 weeks of uptake, and irrigation has to be drained before it. (Warm-season fertilizer is the exception: Southern extension programs cut nitrogen off on a calendar date, not a frost offset, because the Deep South frost arrives long after the grass stops growing.) Montana's typical first frost is September 22; see the Montana frost dates page for the early/late brackets and city table.

Common questions

Montana lawn care FAQ

When should I overseed my lawn in Montana?

When should I fertilize my lawn in the fall in Montana?

When do you plant garlic in Montana?

When should I aerate my lawn in Montana?

When should I winterize my sprinklers in Montana?

When should I apply pre-emergent in Montana?

When is the last time to mow in Montana?

What kind of grass grows best in Montana?

Keep planning

The rest of your Montana fall

Montana first frost datesTypically September 22, the anchor for every date on this page.Live soil temperature mapYour ZIP's 6 cm reading, 14-day trend, and germination thresholds.Montana fall foliagePeak color usually lands right in the overseeding window, so plan both.Montana tick forecastTicks stay active in leaf litter until a hard freeze, so check before yard work.

More Rockies lawn calendars

Windows are climatological typicals computed from NOAA 1991 to 2020 frost normals and grass-zone rules, cross-checked against Montana State University Extension guidance. Any single year runs ±2 weeks; live soil temperature (Open-Meteo, 6 cm) is modeled, not measured. National tool: fall planting calendar by ZIP → Hero image: “2022-10-26 08 11 53 Fallen Red Maple and Saucer Magnolia leaves on a lawn in autumn along Aquetong Lane in the Mountainview section of Ewing Township, Mercer County, New Jersey” by Famartin, CC BY-SA 4.0