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How to Plant Old Grass Seed

Many of us have found an old bag or box of grass seed in the back of the shelf of cabinet in the garage and wondered if it would grow. The answer, of course, is “Maybe.” Depending on how it has been kept and how it is planted, grass seed can remain viable for years. Seed grows to maturity with a set of biological preconditions that “program” it to germinate only under conditions that allow the plant to survive. As each year passes, only the strongest seeds survive.

Test seeds for viability by counting out 100 seeds and scattering them in potting soil in an empty milk carton or other container. Put your “test batch” in a sunny window and keep it moist, not wet, for several weeks until the grass is up. Count the number of blades to determine the percentage of germination you can expect.

Top-dress your lawn bed with compost mixed with an equal part of humus or manure. Work the top dressing in well to create an optimally fertile bed.

Remove all rocks and weeds. Break up clumps of dirt so that the soil is fine enough to rake flat. Level the lawn bed as you go so that water does not stand in puddles.

Scatter seed in early fall according to the corrected germination rate. For example; if the original germination rate was 97 percent and the actual germination rate is 50 percent, spread the seed at twice the rate as normal. Water gently but well so that the seed settles into the soil.

Keep the seed moist until germination. Water young grass in the early morning to minimize the chance of evaporation or fungus due to water sitting overnight. Wait to mow until the grass reaches 3-4 inches tall and remove only a third of the leaf.


Most viable grass seeds will germinate within a few weeks in your test patch but if you’re testing Kentucky bluegrass, you may have to wait; its germination period may be three to four weeks, depending on conditions.

Put the grass seed in the refrigerator for a few days while you prepare the lawn. Pour it into a plastic bag and spray it with distilled water or weak tea to moisten it then place it in the vegetable bin to “stratify” the seeds to simulate winter’s chill.

Soil temperature should be about 60 degrees for successful grass seed germination. Warm season seed may begin germinating in soil that is a few degrees warmer but for the best results don’t rush planting.

Plant old grass seed in early fall (particularly if you just plant the seed without finding its corrected germination rate) so that you can over-seed in spring if necessary. A thin lawn will perish—or be overgrown with weeds—during a hot summer.


Perennial grass seed types lose viability by percentages each year but annual rye grass, which is included in many mixes for “quick cover” is remarkably long-lived. If you have an old mixture with annual rye grass in it, you may have a worthless sack of rye.

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