When should I be seeding a lawn?
Early spring and fall tend to be the best time for seeding a lawn but in the right situations you can sow grass at any time of year. However seedlings trying to grow in a hot summer or harsh winter may need a lot more care than usual if they germinate at all.
In terms of temperature grass seed can germinate between 45 and 65 degrees Fahrenheit (7 and 18 degrees Celsius). Different varieties can be sold as warm and cool season at each end of that range but check the packaging to make sure. Ground temperature is a few degrees below air temperature so sowing a lawn is possible during a cool summer or very mild winter. A heavily shaded lawn may tolerate sowing in warmer temperatures as long as you are careful about watering.
Heavy rain should be avoided if it can be predicted or unless your soil has good drainage. Ideal soil for germination should be damp but crumbly.
Preparing ground for a lawn
It is worth doing a pH test a few months before you are planning to sow as additives can take time to change the acid/alkaline balance. See our article on pH Levels – Soil Acidity and Alkalinity for details.
Make sure there are no plants/weeds in the patch of ground to be sown. If you prefer the eco-friendly option I can recommend doing it by hand. It’s good exercise, you can get the family involved and so much more satisfying. But you can use herbicides if you have to, just make sure you use non-residual one a few weeks before to give it time to dissipate before it kills the new seeds. Also cover the trunks and any exposed roots of trees nearby to make sure no herbicide gets on them.
Get rid of any bricks, stones, plastic or other inorganic materials. If you have moved into a new house it is common to find builders rubble in the soil and sometimes a lot of it. If it isn’t practical to remove it all at least consider trying to redistribute it to make things level. When the soil settles a bit you don’t want lumps where rubble was or a sharp object just below the surface where a child could fall on it.
Use a garden fork to break up the soil a bit to a depth of 100mm. This is a good opportunity to do any leveling on the area. If you need to make any major changes such as creating or flattening a steeper slope, take off the topsoil first then lay it back afterward. It isn’t good to mix it with the soil below. Using pegs and string as guides can help in making surfaces flat.
You may want to add things to assists drainage or moisture retention at this stage as well. If the soil tends to be quite dry and/or sandy you can add compost or decomposed manure to help hold moisture. If it doesn’t drain well you could add sand. Clay soil which doesn’t drain well may benefit from compost or decomposed manure to try and break up the fine-grained structure a bit as well as sand. It is also possible to lay drainage pipes or a soakaway if the drainage is particularly bad. As mentioned above the ideal soil conditions should be damp but crumbly. If you add anything organic then you should dig it to at least 150mm.
Rake the top 30mm to break that up properly to a decent tilth. It should be broken up his way to provide a greater surface area and ensures that the seed can make good contact with the soil. It can’t do that with clumps. Rake from several directions to keep things flat and even and rake while walking backwards to avoid treading on the tilth. You should try to do this about a week before sowing to allow the freshly turned topsoil to settle a bit.
If you plan to use fertilizer it should be added 2-3 days before sowing. The best kind to use for a new lawn is usually labeled ‘starter fertilizer’ and is high in phosphorus. If you didn’t add compost earlier you could also add soil conditioner.
Also a few days before it may be worth giving the area a light watering if the soil has dried out and no rain is due. Not too much though, you don’t want the seeds sitting in water.
If a few weeds appear during the week you leave it they can be removed before sowing. When the grass starts growing it should be dense enough to crowd out weeds. If there are significant weeds though it may be best to consider using a non-residual herbicide and wait the recommended time for it to dissipate before seeding.
Finally rake it once more and lightly compact the soil (with your feet or a roller). This is make the seeds stay near the surface and not drop down into gaps where they won’t shoot enough to reach sunlight. Remove any stones that may have appeared while the soil was settling.
Sowing the lawn
If you haven’t already, see my article on choosing grass seed to get the mix that will work best for you.
You don’t want to be seeding a lawn on a windy day. Apart from the chance of seed blowing away from the lawn area it can also make the sowing uneven and you could end up with uneven patchy grass.
Make sure you have picked the right kind of seed and have the right amount for your lawn area. Apart from the cool/warm season seed mentioned earlier there are varieties for ornamental gardens, hard-wearing lawns (for kids and pets) and some meant for shady areas. Around 50g per square meter is a good rule of thumb but check the packaging for specifics for that type. Also check the germination rate which they should specify. Most should be around 90%-95% but some are less so it is better to add a bit extra. Old seed also germinates less, as much as 20%-25% per year less so it is best to get new seed and not cheap, old stock for the same reasons. You can always keep any left over for overseeding in the following year.
Sowing time at last! It is best to sow the seed in several passes to make sure seeds get distributed evenly. It is easy to lay the seed slightly too thickly and start running out towards the end of the lawn if you try it in one shot. Split the seed into 3 or 4 equal amounts and try to cover the ground equally on each pass. You can sow by hand, making sure to sprinkle it evenly, use a hand-held seed spreader or one that you push.
Lightly rake then compact again. To germinate and take nutrients the seed must have good contact with the soil. Only half of the seed will be covered, that’s fine.
If the air is dry you can put clear plastic sheeting over the area to help trap moisture. This will trap heat as well though so not so good in hot temperatures especially if the lawn will be in direct sunlight. You will still need to water the plot though so make sure you remove he sheeting first. Also if you get rain, pull the sheeting back afterwards to avoid waiter pooling and remove it once you start seeing shoots.
The seeds should germinate and show shoots within 7 to 21 days depending on the weather and seed variety. If possible protect the seeds from birds if you get a lot in your garden. Chicken wire, fruit netting or string with foil suspended above the soil can all help with that.
Try not walk on it until it reaches about 25mm in height. If it is in a public area or you have kids that may visit for example, it can be worth setting up a simple cane and string barrier to mark off the area to let them know they shouldn’t be going past. If you have to get out into the middle, to weed for example, use a board or sheet of wood to distribute your weight rather than walking directly on the seedlings. It will squash down some shoots which should bounce back, but it is preferable than taking out everything your foot covers.
New lawn care
The soil should be kept moist enough that you can push a finger into it without much effort. You can use a fine lawn sprinkler or hose with spray attachment. If your watering method has a ‘mist’ setting, even better. Don’t make it too wet though or seeds can float and clump together and/or rot. Most of the time it will need light watering 2-3 times a day so you don’t give the seeds too much at a time.
If your schedule won’t allow watering 2-3 hours a day you might want to look into an automated irrigation system although this will obviously make seeding less cost-effective.
Remove any weeds before they flower.
When the new grass is 25mm high gently roll with light garden roller or tread it as you did before seeding. If you have a cylinder lawn mower you can use that but set the blades as high as they can go, you don’t want to cut the grass yet.
When grass is 75mm, you can give it it’s first mowing to about 50mm. If not using a cylinder mower, retread or roll after mowing. Collect the clippings by rake (or mower attachment) rather than letting them lie on the lawn. Each time you mow it from then on cut a bit shorter but do not cut below 25mm in the first season.
It will be ok to walk on and lightly use the lawn during the first season once you start mowing it. The root system won’t be established enough to hold up to running and being pushed around though such as pets and kids playing on it.
If all goes well you will end up with a good, new lawn that will last for years. If the grass isn’t as dense as you would like it can always be overseeded the following year.