Renovating your lawn in autumn: overseeding, sowing a new lawn or turf rolls?

By late summer many lawns show the marks of the hot season: thin areas, yellow or dry patches, weeds that have taken hold. It is tempting to wait until spring to sort them out, but for the lawns in our gardens early autumn is almost always the best time to act.

If you first want to understand why your lawn has deteriorated, you will find the most common causes in our guide to yellowing lawns.

Why is autumn the best time to renovate a lawn?

In autumn the soil is still warm from the summer, the air is cooler and there is usually no shortage of moisture: ideal conditions for the seed to germinate and for the young seedlings to root before the frosts (Royal Horticultural Society). Weeds grow less than in spring, and a lawn sown in autumn has two cool seasons, autumn and spring, to establish itself before the first summer heat (Penn State Extension).

Soil temperature matters most. Lawn grass seed germinates fastest from about 10 °C upwards (Hauert technical data sheets), and below 7 °C germination almost stops altogether (RHS). On the valley floors and near the lakes the soil generally stays mild until October; in the side valleys and at higher altitudes it is better to bring the work forward to September.

Overseeding, sowing a new lawn or turf rolls: which should you choose?

It depends on how badly damaged the lawn is and how quickly you want to be able to use it again:

• Overseeding: the lawn is thin or has a few patches, but good grass still covers most of the surface. You sow over the existing lawn without removing it.
• Sowing a new lawn: the lawn is more bare than green, full of weeds, or the soil underneath is compacted and uneven. You remove the old turf, prepare the soil and sow from scratch.
• Turf rolls: you want a green lawn straight away, or the area is on a slope and rain could wash the seed away. It costs more than sowing, but the result is immediate.

How do you overseed a lawn, step by step?

• Mow the lawn short, to about 4–5 cm (Iowa State University).
• Remove the thatch, the layer of dead grass and moss on the surface, by scarifying, or aerate the soil with a hollow-tine aerator. The seed needs to reach the soil.
• Sow evenly, about 20 g of seed per m² (Hauert data sheet for lawn renovation); make two passes in crossing directions so you do not leave gaps.
• Cover lightly with a thin layer of sandy topsoil or go over it with a rake, then roll it or firm it down with your feet, so the seed stays in contact with the soil.
• Water straight away with a fine spray and keep the surface moist over the following days.

How do you sow a new lawn from scratch?

When the old lawn is no longer worth saving, you strip off the turf with its roots, dig over the soil and remove stones and weed roots. Then you level it with a rake, firm it lightly and let the soil settle, so you avoid dips forming after the first rain.

Sowing works as for overseeding, but with a little more seed: about 25 g per m² for a new lawn (Hauert data sheet). After sowing, rake lightly, roll and water. For a home garden, a mix of different species suited to the aspect is the best choice: the species most commonly found in mixes are perennial ryegrass, tall fescue, red fescue and smooth-stalked meadow grass.

How long does grass seed take to germinate?

Each species has its own timing, and in a mix some species come up well before others. Approximate germination times (University of Tennessee Extension):

• perennial ryegrass (Lolium perenne): 3–7 days;
• tall fescue: 6–12 days;
• red fescue (Festuca rubra): 6–14 days;
• smooth-stalked meadow grass (Poa pratensis): 14–21 days.

That is why a newly sown lawn can look patchy for the first few weeks: this is normal, the slower species come through later.

How much should you water the lawn after sowing?

Little and often: for at least two weeks, and until the whole mix has come up, the soil must never dry out, because a seed that has started to germinate and is then left dry will die (Hauert technical data sheets). A light watering every day is needed, twice on hot or windy days, enough to moisten the surface without creating puddles or moving the seed (University of Tennessee Extension). Once the lawn has come up, you gradually switch to heavier but less frequent watering. This applies only to a newly sown lawn: an established lawn is watered deeply and infrequently.

In autumn the rain often takes care of it, but in dry weeks a programmed irrigation system helps make sure you do not miss a day.

How do you lay turf in autumn?

Autumn is also an excellent time for laying turf: with the cool, moist conditions the rolls take well and need less water than in summer (RHS). To help the turf root well:

• prepare the soil before delivery: dug over, levelled and lightly firmed;
• lay the rolls within 24 hours of delivery if possible, because when rolled up they heat up and deteriorate (RHS);
• butt the rolls tightly against each other and stagger the joints, like the bricks in a wall;
• once laying is finished, roll lightly and water generously, so the water also reaches the soil beneath the rolls;
• for the first 2–3 weeks, walk on the rolls as little as possible (University of New Hampshire Extension);
• make the first cut after about three weeks, once the roots have taken, with the mower blade at its highest setting (RHS).

When should you make the first cut after sowing?

When the seedlings are 5–7.5 cm tall. The RHS advises firming the soil lightly and mowing two or three days later, removing no more than a third of the height. The mower blades must be sharp: on such young grass a blunt blade tears the seedlings out instead of cutting them.

Which fertiliser should you use in autumn?

In autumn you need a feed made for the season, richer in potassium and lower in nitrogen. Leftover summer feed is not suitable: too much nitrogen late in the season produces soft growth that is more vulnerable to disease over winter (RHS). If you want to be sure, a soil analysis shows how much potassium and phosphorus are actually needed (Penn State Extension).

Which mistakes should you avoid when renovating a lawn in autumn?

• Sowing too late: in cold soil the seed does not germinate and is left exposed to birds and rain.
• Letting the soil dry out in the first weeks after sowing.
• Sowing onto thick thatch without scarifying: the seed does not reach the soil and the seedlings dry out.
• Walking on the new lawn or freshly laid turf before it has rooted.
• Mowing too early or too short, or using a nitrogen-rich summer feed.

Nikola Giardini e Figli SAGL takes care of lawn maintenance, overseeding and laying turf rolls throughout the canton of Ticino, from the Locarnese to the Luganese and the Mendrisiotto. If your lawn needs renovating and you would rather leave the job to someone else, we can come and take a look: the site visit and quote are free.