Will grass seed grow after heavy rain? 3 ways to rescue it if your lawn is waterlogged

If, like me, you sowed fresh lawn seed before the weekend storms, you’re probably wondering the same thing I am: Will grass seed grow after heavy rain?

Autumn is one of the best times to sow grass seed, but after high winds and torrential downpours, it’s not looking good for budding lawns. Grass seed needs moist conditions to sprout, it’s true – but too much water can be detrimental to germination and growth.

Will grass seed grow at all after heavy rain, though? I asked the experts – and found out what to do if your lawn seed is at risk after the stormy weather.

So, will grass seed grow after heavy rain? Thankfully, the wet weather won’t spell definite doom for our lawns-to-be – with a few caveats.

‘In many cases, yes, it will grow,’ says Guy Jenkins, consumer manager at Johnson's Lawn Seed. ‘In fact, moisture is key to grass seed germination. However, you don’t want the area to be completely saturated or waterlogged, as this will have an effect on the germination.’

If you haven’t spotted severe waterlogging on your lawn, your grass seed might be okay – it all depends on how well the water drained away.

‘If the rain has drained away or soaked into the soil after a heavy downpour and the ground is moist but not waterlogged, grass seed should germinate as normal,' says Jonathan Davis, lawn care expert at Lawnsmith.

‘The problems arise when water pools on the surface where grass seed has been sown. Seeds left sitting in standing water can rot and be starved of oxygen, so they won’t grow. Sadly, a lot of grass seed is wasted this way.’

Jonathan also notes that heavy rain can wash seeds away or push them into clumps, explaining, ‘You’ll still get growth, but it tends to result in a patchy lawn with thick tufts in some places and bare soil in others.’

How to rescue grass seed after heavy rain

If you spot signs of water pooling or flooding, these lawn care tips might just save your grass seed...

What you'll need

1. Redistribute the seed

If you haven’t improved your lawn drainage fast enough and you’re worried that heavy rain has gotten the better of your grass seed, start by checking if the seed has been washed into patches.

‘If seed has moved and bare areas have appeared, wait until the ground is workable and then use a rake to redistribute the seed across the affected areas,’ advises Guy from Johnson's Lawn Seed.

If you’re in need of a new rake, this Verve Landscaping Rake from B&Q is top-rated.

‘You should typically start to see germination within seven to twenty-one days,’ Guy adds. ‘If the lawn is noticeably patchy after this period, overseed the affected areas to help achieve a thicker, more even lawn.’

I’ve used Westland PureGreen Lawn Seed (also available at B&Q), and it’s sprouted successfully regardless of the stormy weather.

2. Aerate your lawn

If, however, your lawn has flooded, it's worth learning how to aerate your lawn.

‘If heavy rain is forecast, aerating your lawn is the best defence for your seeds,’ says Jonathan from Lawnsmith. ‘Aerating creates small channels in the soil so water drains through it instead of pooling on the surface or running off.’

You could use a garden fork to aerate your lawn, or invest in a dedicated tool like the Crystals Metal Lawn Aerator from Amazon. Jonathan recommends keeping aeration light at this time of the year to avoid disturbing the seed or stressing the existing lawn, so try to stick to the waterlogged areas first.

3. Cover the seed

You could also cover the grass seed with some topsoil, like this Westland Lawn & Turf Dressing from Crocus, to add another layer of defence.

‘A thin layer of topsoil or compost will help seed stay in place and improve lawn drainage,’ explains Jonathan.

‘You could also cover your seed with a light, natural material to prevent the seeds being washed away, which keeps birds from eating the seed, too.’

If you’re sure your grass seed is beyond help and want to try again with added protection, you could even try this H2O GrowTrax Lawn Repair Fabric from Argos, which contains seed, fertiliser and mulch in a single roll.

So, grass seed will germinate after heavy rain – you'll just need to keep an eye out for any waterlogging and tackle flooded areas as soon as you can.