Why Grass Seed doesn’t Grow!

Grass seeds can quickly germinate and grow into a lawn if you get the planting, moisture and temperature right. Here are some very common grass seed sowing mistakes.

It’s Too Cold for Grass Seed

The weather can be deceiving and tempt you into planting grass seed at the wrong time. Spring and autumn temperatures can be warm by day but drop near freezing at night. This means the soil temperature may be cold.

If you've been watering or it’s been raining, this will reduce the soil temperature even more, exacerbating the problem. Shady areas will also have a lower temperature.

This means considering temperature, weather, and location when deciding if it is warm enough to plant grass seed. Your target should be an average day-night temperature of at least 8 degrees but nearer 12 degrees. For example, a spring night temperature maybe 2 degrees with a day temperature of 14 degrees. This will give you an 8-degree average, which is not ideal, so wait for warmer weather.

You let the Grass Seed Dry Out

In the article All About Grass Seed Germination, you will understand the importance of constant moisture. If you water, let it dry, water again, and so on, then the seed never germinates. The golden rule is NEVER LET SEED DRY OUT. 

It's too Dry

Dry springs are becoming more and more common, meaning little moisture in the soil by the time you come to plant your seed in the soil at the correct temperature. Keeping the seed moist under these conditions is an uphill battle. If you haven't built a moisture reservoir in the soil by watering for a few days before seeding, preventing the seed from drying out with frequent daily light watering is virtually impossible. The best way to combat dry springs and/or cool soil temperature is to build a moisture reservoir, plant the seed and incubate it under polythene sheeting. This prevents evaporation, warms the seed, keeps it moist and protects it from birds and the elements.

Thatch, Moss or Debris remains after Scarifying or Raking

When seeding, the seed must contact the soil. Any remaining vegetative debris puts a barrier between the seed and the moist soil. The seed germinates, but the little root shoot that emerges can't reach the soil, so it dries out and dies. You need to always seed onto bare soil.

Compaction

This applies only if the soil has not been dug, which occurs when seeding bare patches or scarifying existing lawns. Compaction prevents the soil from holding the water and air roots required to develop. In addition, if the soil surface is hard, baby root shoots may not be able to penetrate.

Planting Grass Seed too Deep or Using Top-Dressing

Grass seed must be on the surface and no more than 2-3mm deep. It must also be in good contact with the soil by treading in or lightly rolling. Plant it too deep or cover it with more than a very thin layer of soil or top dressing, and you may stop it from germinating.

The Grass Seed is Too Wet

Being too enthusiastic about watering your lawn, particularly on clay soils that easily waterlog, can cause problems. Once germinated, the seed needs oxygen to survive, and water-logged soil means it will drown. 

Do not Cover Grass Seed with Peat or Compost

When repairing patches, people sometimes cover them with peat or compost. Unfortunately, if the compost dries out, it will draw moisture away from the seed, preventing germination or growth.

Seed is Old

This is most unusual, as grass seed can be kept for several years and still be reasonably viable. However, how it is stored usually causes poor germination in seeds older than a few months.

Stored Incorrectly

High temperatures, humidity, light and sweating are the biggest seed killers.

Storing in a cool, dark basement or garage is probably the best place, though basements can be humid. Away from light is easy, so the main aim is to keep the grass seed dry and cool. Garden sheds get very hot, quickly ruining your seed in days. This would be perfect if you have an old fridge and not much seed to store.