Quite often the seeding rate on your grass seed bag is given as a range. This is particularly true for over-seeding rates on lawns. Here is a short guide on how to decide when to use high or low grass seeding rates assuming your seed has a high purity rating and pedigree.
Patching or Minor Repairs
It’s going to be difficult to calculate seeding rates for a few square inches or metres of lawn. Most home owners put in far too much seed which causes strange dense tufts later in the year. Therefore put seed in at between 10 and 20 seeds per square inch. That will be plenty, I promise.
If you are determined to mow your lawn as close as is tolerable for that type of grass then increase seeding rates by 20 to 30% above the highest rate
Clean Seed Bed
If when establishing a new lawn you have spent a lot of time and patience preparing a weed free soil you can lower seeding rates to perhaps half the recommended amount. It will take slightly longer to establish and thicken however. If you haven’t done anything to kill or remove weeds other than dig them in then add 20% to the higher seeding rate.
Time & Timing
If you need your lawn to establish or recover and be useable as quickly as possible increase seeding rates by 20 to 50% above the highest rate.
If you are seeding in less than ideal conditions (cold or dry) increase seeding rates by up to 100% to compensate for losses. However, most seed won’t germinate below about 80C (except Lawnsmith Coolgreen) or if conditions are too dry.
Over-Seeding after Raking or Scarifying
It is always a good idea to over seed after scarifying as this helps the return to a dense turf as quickly as possible. It is also a good opportunity to introduce new types of grasses for an improved lawn.
Depending on how heavy you’ve been with the scarifier determines how much seed to add. A light scarifying may only require a half rate of seed, a typical autumn scarify may require seed at the new lawn rate whilst a heavy scarify which has been into the soil should be over seeded by up to 50% more than the new lawn rate.
Increase the seeding rate by perhaps 10% for every year the grass seed has been kept. Some seed kept in cool, very dry and dark conditions lasts for many many years. However, if you have an important job to do best use fresh seed or test your seed before use.
To test old seed:
Take an old clean cloth and fold it into a flat pad about an inch thick. Place this in a tub or bowl with half an inch of water. The cloth will soak up water and become saturated. The top of the cloth pad is now an ideal place to sprinkle perhaps 20 to 25 seeds.
- Place the tub in a warm place away from drafts – airing cupboards and utility rooms are usually ideal
- Maintain a water level of about half an inch until germination
- Germination will take between 5 and 14 days depending on seed type and temperature
- When sprouting gets to ½” count how many seeds did and how many didn’t germinate
- If only half germinated double your seeding rate
- If less than half germinated throw it away and buy fresh!