Do you want to transform your lackluster yard into a lush green landscape? Try planting new grass seed to cover those bare areas and give your home more curb appeal. Grass grows fast, it’s cost-effective, and it doesn’t need much maintenance.
Many homeowners have a leftover bag of grass seed from their previous planting, but if it’s been a few years, you may question whether it’s worth planting. How long does grass seed last?
Whether you’ve got some extra seeds at home or plan on buying some, you need to assess your seeds’ viability for successful planting.
Does Grass Seed Go Bad?
Like any other seed, grass seeds lose their capacity to grow over time if not stored properly. When buying seeds, always check for the germination rate and the test date.
Germination Rate
Germination rate is an estimate of the number of seeds that will successfully sprout in a packet. Seed quality, harvesting conditions, and production location heavily influence the germination rate.
Always buy from a reputable distributor to ensure you get a quality grass seed. Depending on the grass variety, you should aim for an 80% to 95% rate.
Test Date
The test date shows you when the manufacturer tested the seeds’ germination rate. The rate should remain the same within the first year after the test date unless improperly stored. Every subsequent year of storage lowers the germination rate by 10% to 20%.
We recommend storing your leftover seeds under optimal conditions to preserve their germination rate as much as possible.
Storage Factors Affecting Seed Viability
The ideal conditions for seed storage is a cool, dry, and dark space. If your seeds have been exposed to moisture, make sure to dry them properly before storing them in a sealed container. Consider these storage factors:
Humidity
Seeds kept in open containers or sacks can absorb the surrounding moisture, especially in humid climates. Always aim for the lowest possible humidity, but 30% relative humidity or lower will keep your seeds safe. If you store your seeds in a sealed container, you won’t have to worry about moisture.
Temperature
Try to keep your storage temperature above freezing but under 60oF, and aim for consistency. Fluctuating temperatures can negatively affect seed viability. Any storage condition above 100oF can also damage your seeds.
Potential Openings
Without a properly sealed container, you risk exposing your seeds to pest infestations. Rodents and other pests can damage your seeds by eating their interior and leaving the husk.
Sun Exposure
Grass seeds can’t tolerate direct sun exposure. If you plan to store your seeds in a bright room, make sure to cover their containers with thick material.
Seed Type
The type of grass influences the longevity of their seed viability. Take the time to look for a species with long-lasting seeds that can thrive under your outdoor conditions.
One study from Oregon State University shows that a 50% average of perennial ryegrass, tall fescue, and Kentucky bluegrass seeds can still germinate after three to five years of storage in ideal conditions, and 50% of creeping bentgrass seeds remain viable over five years.
Germination Test
You don’t want to waste your time planting grass seeds that won’t grow. You can avoid growth failure by testing your seeds’ germination rate before you plant your entire lawn. Use this step-by-step process:
- Place a dampened paper towel on a flat surface. Lay ten seeds on the towel in a row, and roll up the towel.
- Store the paper towel in a zip-lock plastic bag and leave it in a warm room for a week. Then, take the towel and count the sprouted seeds.
- For every seed sprouted, add 10% to the germination rate. If you plan on using seeds with a 50% rate or lower, consider doubling the number of seeds to plant or purchase new seeds.
Reasons Your Grass Didn’t Grow
If your seeds had a high germination rate, but the grass planting still wasn’t successful, you may have another problem with your growing conditions. Consider the following factors to find out the culprit of your poor grass growth.
Sub-Optimal Temperatures
Temperature influences most plant processes, and grass seeds usually prefer soil temperatures of 55oF and air temperatures of 60oF.
However, optimal growing temperatures vary depending on the type of grass. Always double-check the desired growing season for your selected grass before you start planting.
Excess Water
If you’re a gardening beginner, you might be inclined to over-water your grass. Too much water can slow germination or stop it altogether.
Never plant grass during the rainy season, so you can fully control the water intake.
Weed Growth
Weeds tend to have a more forgiving germination temperature range than grass. Many weeds grow aggressively, and they can rob your grass seeds of vital nutrients and moisture.
You can use an herbicide that you can apply during seeding or remove weeds by hand.
Lack of Sunlight
Planting grass in shadier areas can significantly hinder their growth. If your planting area gets less than two hours of sunlight each day, you may want to choose another spot.
You can cover low-light areas with other plants like ivy or pachysandra instead.
Soil Quality
Your soil must have the required plant nutrients, including nitrogen, potassium, and phosphorus. If you’re having trouble getting grass to grow, low-quality soil might be the root cause. Apply the appropriate fertilizer and check your soil’s pH levels for optimal grass growth.