If you have recently sown new grass seed, frost can damage or kill the tender new shoots before they have a chance to establish. There are several steps you can take to help protect your lawn during cold snaps in fall and spring.
Should I be concerned about frost with new grass seed?
Yes, new grass seed is very vulnerable to cold temperatures. Grass seed needs consistent soil temperatures of at least 55-65°F to germinate and survive. Frost and freezing temperatures, generally below 32°F, can damage or kill new grass shoots and seeds. The soil itself provides some insulation from cold air temperatures, but cold snaps can still cause issues.
Frost is most likely to be a problem when sowing cool season grasses like fescue and bluegrass in fall or spring. While these grasses can handle cold winters once established, they are vulnerable in the first few weeks after seeding. Newly seeded warm season grasses like bermuda grass are also susceptible in spring.
How can I tell if frost has damaged my new grass seed?
If temperatures dip below freezing, check for visual signs of damage. Frost-damaged grass blades will turn yellow or brown. The grass may also appear dried out or desiccated. Damaged seedlings may wither and die. Healthy grass blades will maintain a bright green color.
In addition to discoloration, frost can prevent seeds from germinating properly. If it has been several weeks since sowing and there is little to no grass growth, cold temperatures may be preventing germination.
What are some ways I can protect grass seed from frost?
Here are a few tips to protect newly seeded lawns from frost and freezing:
- Cover seeded areas with straw, fabric row covers, or insulation blankets. This provides insulation against cold air.
- Avoid sowing grass seed too early or too late in fall or spring when frost risk is high.
- Use cold tolerant grass varieties like fine fescue that can better withstand frost.
- Apply fertilizer to help young grass establish roots faster and become more cold hardy.
- Water lightly before frost to keep soil warmer overnight.
- Cover seeded slopes which lose heat more quickly. Pay extra attention to low areas.
Use row covers, straw, or blankets for insulation
Covering newly seeded areas with protective materials traps heat and acts as insulation against cold air and frost. Some options include:
- Straw: A 1-2 inch layer of loose straw protects tender grass shoots. Avoid hay which may contain weed seeds.
- Row covers: Fabric row cover material allows light and air circulation while providing a few degrees of frost protection.
- Insulation blankets: Designed for new lawns, these heavyweight blankets provide the best cold protection.
Be sure to remove any coverings as soon as temperatures warm and the threat of frost has passed. Leaving the covers on too long can cause new grass blades to overheat once daytime temperatures rise.
Seed at the right time of year
Pay close attention to historical frost dates and temperature patterns for your area. Typically the best times to seed grass are:
- Spring – 4-8 weeks before the last expected frost
- Fall – 6-8 weeks before the first expected frost
Avoid sowing right before or after likely frost periods. Local university agricultural extensions can provide planting date guidelines specific to your region.
Select cold hardy grass varieties
When sowing in early spring or late fall, choose grass seed blends labeled for cold tolerance. Varieties like fine fescue and perennial ryegrass recover quickly from cold damage. Here are some other cold hardy grass types:
| Grass Type | Cold Tolerance |
|---|---|
| Fine Fescue | Excellent |
| Perennial Ryegrass | Very Good |
| Tall Fescue | Good |
| Kentucky Bluegrass | Moderate |
Fertilize for faster root establishment
Applying starter fertilizer when seeding encourages faster root growth so grass plants can better withstand frost. Look for fertilizers high in phosphorous. Follow product labels for correct application rates.
Once the new grass has been mowed 2-3 times, switch to a balanced turf fertilizer to promote deep roots and cold hardiness. Avoid late season fertilizing which can trigger tender new growth prone to frost damage.
Water lightly before a frost
Lightly water new grass the day before an expected frost. Just a short 5-10 minute watering is sufficient. This helps insulate the soil and keeps it warmer overnight.
Avoid heavy watering which can have the opposite effect, especially if temperatures drop below freezing. Excess moisture can actually draw heat out of the soil and make it more prone to freezing.
Pay extra attention to slopes and low areas
Sloped areas and low spots lose heat more rapidly on cold nights as dense, cold air naturally settles in these locations. Be sure to cover seeded slopes and give extra protection to low areas with added insulation.
What do I do if my new lawn is damaged by frost?
It takes most cool season grasses about 2-3 weeks to become established enough to tolerate mild frosts. If frost strikes before that and causes dieback or germination failure, you will unfortunately need to reseed the damaged areas.
Here are some tips for reseeding after frost damage:
- Gently rake up any straw or dead grass blades from damaged areas before reseeding.
- Reapply starter fertilizer to encourage fast root growth.
- Make sure to maintain consistent soil moisture for the new seed.
- Be prepared to redo frost protection steps like using row covers.
- If possible, wait for warmer temperatures before reseeding.
With proper frost care and protection, you can still successfully sow grass seed in fall or early spring. Just be diligent about keeping a close eye on weather forecasts for cold snaps. Take action to insulate tender new seedlings whenever frost is a risk. With some extra attention, you can safely establish a beautiful new lawn during cooler transitional seasons.
Conclusion
Protecting new grass seed from frost requires advance planning and preparation. Pay close attention to frost dates and air temperatures when scheduling spring and fall seeding. Use insulating materials like straw and fabrics to protect tender grass shoots and seeds. Seed cold-tolerant grass varieties at recommended planting times. Avoid heavy watering before frost, which can draw heat from the soil. Be ready to re-seed any areas damaged by unexpected cold snaps. With proper frost care, you can safely establish new grass growth in periods of fluctuating weather.
