What happens if too cold for grass seed?

Quick Answer

If it is too cold for grass seed germination, the seeds will likely fail to germinate and establish. Grass seeds require soil temperatures between 50-65°F for successful germination. If temperatures are consistently below 50°F, grass seed will remain dormant until warmer temperatures arrive. Patience is key when seeding in cold weather.

What is the ideal temperature range for grass seed germination?

Most cool season grass seeds germinate best when soil temperatures are between 50-65°F. Below 50°F, the rate of germination drops off sharply. Warm season grasses prefer soil temperatures above 65°F for germination. Here are some approximate soil temperature requirements for common grass types:

Grass Type Preferred Soil Temperature Range
Kentucky Bluegrass 50-65°F
Perennial Ryegrass 45-65°F
Tall Fescue 45-65°F
Fine Fescue 45-65°F
Bermudagrass 65-85°F
Zoysiagrass 65-90°F
Buffalograss 65-85°F

As shown, cool season grasses prefer 50-65°F, while warm season grasses require 65°F or warmer. Seeding cool season grasses when soil temperatures are below 50°F is risky and may result in failure.

What happens if you plant grass seed when it’s too cold?

If grass seed is planted when soils are too cold, a few things can happen:

Failed germination

The most likely outcome of seeding when it’s too cold is that the grass seeds will fail to germinate. Seeds often require a combination of moisture, warmth, and oxygen to trigger germination. Cold soils don’t provide adequate warmth for the germination process. The seeds remain dormant until conditions improve.

Rotting of seeds

In some cases, grass seed sown in cold, excessively wet soils will rot before germinating. The seed coats rupture before the embryo inside can start growing. This points to the importance of having adequate drainage when seeding in cold weather.

Patchy germination

You may get patchy or uneven germination when seeding in marginal soil temperatures. The seeds that managed to germinate quickly outcompete those that germinate later, resulting in thin spots and bare patches.

Slow establishment

Even if seeds successfully germinate, cold weather will slow the growth and establishment of newly-emerged grass plants. The grass may take weeks or even months to fully mature and thicken up under cool temperatures, leaving you with a sparse lawn.

Will grass seed grow in cold soil?

Grass seed can potentially grow in cold soil, but the chances of success drop considerably as soil temperatures go down. Here are some general guidelines:

– 50-65°F – Best temperature range for cool season grass seed germination and growth.

– 45-50°F – Marginal temperatures. Germination and growth will be slow. Higher risk of failure.

– 40-45°F – Most cool season grasses will remain dormant below 40°F. Germination unlikely.

– Below 40°F – Almost no chance for germination and growth. Grass seed will remain dormant.

The minimum soil temperature required for growth varies slightly between grass species. For example, perennial ryegrass can germinate at temperatures as low as 42°F, whereas 65°F may be required for zoysia grass. But in general, cool season grasses will not thrive in soils colder than 45°F.

How can I know if it’s too cold for seeding grass?

It’s not always easy to know if temperatures are right for seeding grass. Soil temperatures can vary from air temperatures. Here are some ways to gauge whether it’s warm enough:

– Use a soil thermometer to check temperatures at seed depth. This is the most accurate option.

– Pay attention to long range weather forecasts. Consistent periods of cold air temperatures below 50°F likely mean soil temps are too low as well.

– Look at signs of natural plant growth. If wildflowers are blooming and trees are coming out of dormancy, soils are probably warm enough for grass.

– Test by sowing a small amount of seed in a few spots. Monitor to see if it germinates as expected.

– If nighttime air temperatures are consistently below 45°F, conditions are likely too cold for seeding.

Getting professional advice from agronomists at your local extension office is also recommended. They can provide planting guides for your specific area.

When is the best time to plant grass seed?

The ideal time to seed grass depends on your climate and the type of grass you want to grow:

Cool season grasses

– Spring – Late March through May. Fall – Late August through September. Avoid hot summer months.

Warm season grasses

– Spring – Mid to late May once soil warms above 70°F.

– Summer – June through July.

The fall and early spring periods provide the most favorable temperatures for cool season grasses like fescue, bluegrass, and ryegrass. Aim to time seeding around when average soil temperatures in your area reach that 50-65°F target range.

What’s the best way to seed grass in cold temperatures?

While it’s better to wait for warmer weather, you can still increase your chances of success when seeding in the cold using these tips:

– Use cold-tolerant grass varieties like fine fescue that can handle lower temperatures.

– Prepare soil well by loosening, aerating, and clearing debris to promote good seed-to-soil contact.

– Apply starter fertilizer to give seeds the nutrients needed to germinate and establish.

– Use erosion control blankets or tarps to help retain soil warmth and moisture.

– Seed slightly heavier than normal to account for reduced germination rates.

– Plan to overseed again later in spring after soils warmup to fill in bare spots.

– Water gently to keep seeds moist but avoid saturating cold soils.

– Be patient! It can take up to 2-3 months to see results when temperatures are marginal.

Should I cover seeded grass with straw in cold weather?

Yes, applying straw or other light mulch over newly-seeded areas is highly recommended for cold weather sowing. The benefits include:

– Insulates soil and reduces heat loss, maintaining warmer temperatures for seeds.

– Prevents moisture loss through evaporation, keeping seeds adequately hydrated.

– Protects seeds and young grass plants from late frosts.

– Discourages birds from feeding on seeds and disrupting germination.

Only use a thin layer 1/4 to 1/2 inches deep to prevent blocking sunlight needed for growth. Straw mulch will break down over time and won’t need removal. Just be sure to use weed-free straw to prevent introduction of unwanted plants.

Should I water grass seed in cold temperatures?

Proper watering is critical when seeding in cold weather. The general guidelines are:

– Soil should be kept consistently moist but not saturated. Too much water can lead to seed rotting.

– Water lightly and frequently, such as 5-10 minutes per zone 1-2 times per day. Avoid heavy, infrequent watering.

– Reduce watering if soils become excessively soggy or if cold rain is in the forecast.

– Wait until the top 1 inch of soil dries out between watering to maintain proper moisture and oxygen levels.

– Adjust watering as needed based on weather and soil type. Clay soils hold more moisture than sandy.

Take extra care when watering in early spring. Melting snow and rainstorms can easily saturate cold soils during this period. Stay vigilant and be ready to shut off any irrigation if needed.

How long does it take grass seed to grow in cold weather?

The timeframe for grass seed germination and establishment slows down considerably in cold conditions. Here are some general benchmarks:

– Germination – Grass seed can take 2 to 4 weeks to germinate in soil temperatures below 50°F. In warmer weather it may take 5 to 10 days.

– Initial growth – The first shoots and leaves may take 3 to 5 weeks to emerge and be visible in cold weather. This happens much quicker in spring or summer.

– Maturity – It can take 8 to 12 weeks after seeding for the grass to fully mature and develop into a thick lawn in cold temperatures.

– Full establishment – Expect 3 to 5 months minimum for grass to fill in bare spots, develop deeper roots, and become fully established in marginal cold weather.

The process requires much more patience compared to planting in spring and fall when temperatures are ideal. But allowing adequate time is key for cold weather success.

What if my grass seed fails to grow in cold weather?

If a fall or early spring seeding fails to germinate as expected after several weeks due to persistently cold temperatures, don’t lose hope. You have options:

– Wait and see – Grass seed can remain dormant for weeks or months when conditions are poor. Vegetative growth may still occur once warmer weather arrives.

– Overseed – Overseed thin areas in spring once soil temperatures reach 50-55°F to fill in bare spots. Rake lightly before seeding.

– Start over – For large failed areas, rototill and reseed later in spring when soils have sufficiently warmed.

– Switch grass types – Consider switching to a more cold-hardy grass species that handles colder weather.

– Improve soil – Add organic compost to improve moisture retention and nutrients for better seed performance in marginal conditions.

– Seek advice – Consult with local experts to adjust your seeding timing and techniques for future success.

Don’t lose hope if your first attempt fails. With some patience and a few adjustments, you can still achieve a beautiful seeded lawn despite cold temperatures.


Seeding grass in cold weather below 50°F soil temperature carries risks, including delayed germination, sparse growth, and outright seeding failure. But it can be done successfully by selecting cold-tolerant grass varieties, taking steps to insulate soil and retain moisture, increasing seeding rates, and simply allowing extra time. Pay close attention to long range forecasts and be prepared to wait 2 months or longer when seeding in marginal conditions. With the right approach and reasonable expectations, cold weather sowing can result in a lush, beautiful lawn.

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