Plant grass seed in New Jersey between mid-August and late September when soil temperatures are consistently above 50 to 60 degrees Fahrenheit. The only exception is Zoysiagrass, a warm-season variety that you should plant early in its growing season, between mid-May and mid-June.
These seeding windows offer the ideal soil and air temperatures for seeds to germinate and establish here. So knowing when to plant grass in New Jersey essentially sets a strong base for healthy, resilient turf later.
The right conditions for planting grass
In general, the best time to plant cool-season grass in New Jersey is mid-August to mid-September because this is the period when conditions are most favorable for seeds to germinate. The conditions are the key. But the weather doesn’t always behave the way we expect, so be flexible and instead watch for the optimal planting conditions.
Here are the conditions that should be present when you plant grass seed:
Soil pH
Soil pH affects the availability of essential nutrients. Test your soil before you sow new grass seeds. Your soil’s pH should be between 6.0 and 7.5 for cool-season grasses to germinate and grow properly. This range ensures that nutrients like phosphorus, nitrogen, potassium, and trace minerals are most available to the new grass.
Read the soil test results to determine if you need to change your soil’s pH. If your soil turns out to be too acidic (below 6.0), add lime (calcium carbonate) to raise the pH. And if it’s too alkaline (above 7.0), use sulfur or ammonium sulfate to lower the pH.
Soil temperature
Your soil should be between 50 and 60 degrees Fahrenheit for cool-season grasses to germinate well. This temperature range supports optimal enzyme activity to help break down stored food in seeds and stimulate growth.
If you plant later than the end of September, the temperatures will probably have dropped below 50 degrees Fahrenheit, and the seeds will lay dormant and not germinate.
Eliminate the guesswork and invest in a soil thermometer for accurate readings. They’re cheap and easy to use.
Air temperature
The temperature should be pleasant, not too chilly or hot, when you plant grass seeds.
Daytime air temperatures should be somewhere between 60 and 75 degrees Fahrenheit to aid seed germination and proper root and leaf development. Temperatures above this range will likely dry out the grass and cause heat stress to seedlings while lower temperatures will slow or shut down germination.
Moisture levels
Water is essential for seed germination. Keep the soil moist to a depth of 1 to 2 inches during the germination period. Test the soil moisture levels using the methods mentioned in this guide.
You can achieve this by watering lightly but frequently – once or twice daily – so the topsoil stays moist. Adjust the frequency based on weather conditions to avoid overwatering and prevent seed rot and fungal disease. Delay seeding plans if there’s significant rainfall in the forecast.
Plant in advance of the first frost
Aim to seed cool-season grasses about 5 to 6 weeks before the average first frost date so that the grass develops roots before freezing temperatures arrive. This is why we advise seeding early in the fall.
The average first frost in New Jersey generally comes between Oct. 1 and Nov. 20. Don’t bother planting grass after late September; you will simply be wasting your time, energy, and money
Planting times by grass type
Cool-season grasses like Kentucky bluegrass, perennial ryegrass, and fescues do well in our temperate climate. But each one is slightly different, so the optimal planting times vary.
Kentucky bluegrass: Mid-August to early-September because it takes longer to germinate and establish.
Perennial ryegrass: Early to late September since ryegrass germinates quickly and establishes fast, so can be planted late.
Tall fescue: Late August to early September.
Fine fescue: Late August to mid-September because fine fescues also prefer relatively cooler temperatures for germination.
Zoysiagrass (South Jersey only): Mid-may to mid-June.
Ideal time to overseed in New Jersey
Same as seeding a lawn for the first time, late summer to early fall is the best time range to overseed a beaten and battered lawn. This means late August to mid-September when all the environmental factors mentioned above align for proper seed germination and establishment.
For more on building and maintaining your Jersey lawn, see these guides:
The Best Grass Seed for New Jersey Lawns
The Best Grass Seed for North Jersey Lawns
The Best Grass Seed for South Jersey Lawns
Trust the pros
Timing is critical when planting grass in New Jersey, but all that work will be wasted if you don’t also provide proper care for your new lawn once it’s established. That’s where Lawn Love comes in.
Our pros are the best in the business at building and maintaining great lawns. Simply call in a pro to help.
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