How long do sweet peas take to germinate? Experts explain long how you'll need to wait and ways to speed it up

If you’ve decided to plant sweet peas from seed this year, you’ve made a wise choice. These hardy annuals make a lovely addition to the garden, and if you’re about to sow the seeds, you’re probably wondering how long do sweet peas take to germinate.

If kept under the right conditions - a steady temperature between 10–15°C - sweet peas typically take around 10 to 14 days to germinate. Knowing how to care for sweet peas once they’re in bloom will help the flowers thrive, but there’s also some things you can do to speed the germination process along - if you’re not seeing results as quickly as you’d like.

We’ve spoken to gardening experts and asked them the question, how long do sweet peas take to germinate, so you can get a clear picture of whether your sowing has been successful.

How long do sweet peas take to germinate?

Sweet peas tend to take around 10 to 14 days to germinate, if they’re kept in consistent conditions. So, temperatures that don’t exceed 15°C, or drop below 10°C, are ideal, and should give the seeds enough warmth to start the germination process. In colder temperatures, the seeds can take as long as 28 days to germinate.

Knowing when to sow sweet peas can make a world of difference to the germination process. ‘For the best results, aim to plant sweet pea seeds in late October or November, or again in late February or March, as these periods offer the best temperatures and light levels,’ Josh Novell, gardens expert at Polhill Garden Centre advises.

So if you missed the October or November window, seize the opportunity and sow your sweet pea seeds next week. The temperatures over February will create ideal conditions to help them germinate within a fortnight.

How do I know if my sweet peas have germinated?

You will know your sweet peas have germinated if you start to see seedlings emerging through the soil, which should take a couple of weeks. Around a month after sowing, you should also start to notice white roots appearing at the bottom of the pot.

‘Healthy seedlings can also be seen in sturdy, green growth and the first sets of leaves beginning to form,’ Josh explains. ‘These indicate the seeds are establishing themselves and are ready for the next stages of care, such as thinning or potting on.’

Why aren’t my sweet peas germinating?

If it’s been longer than a couple of weeks and you’re wondering why your seeds aren’t germinating, this could be due to a few reasons. If the seeds are outside, mice could be the cause - these pests love sweet peas and can eat the seeds before they even have a chance to germinate. Try adding one of the scents mice hate (peppermint, vinegar, garlic, or clove) nearby to help.

‘Other issues like overwatering before seedlings emerge, planting seeds too shallow or deep, or poor light conditions can also impact germination,’ Josh says. ‘Old or improperly stored seeds may also fail to germinate successfully.’

How to help your sweet peas germinate

There are some tips and tricks that can help get the sweet pea germination process underway. Make sure the seeds are receiving sunlight, and plant them in free-draining soil to prevent water-logging.

You can also try ‘chipping’ the seeds before you sow them. ‘Chipping is the removal of a small part of the outer coating of the seed,’ Graham Smith, gardening expert at LBS Horticulture explains. ‘Use a sharp knife to nick or remove a small piece of the coating on the opposite side to the 'eye' of the seed. This can help germination as some of the seeds have a hard outer coating that can make it harder for moisture to penetrate the seed, which is key for the germination process.’

Soaking the seeds in water before you sow them can also help.

How do you speed up sweet pea germination?

To speed up the sweet pea germination process, you can try using root trainers (available on Amazon). These are deep containers that promote the growth of strong, straight roots.

‘Before you sow the seeds, soak them in a small amount of water (a tablespoon or two) for a few hours,’ Graham advises. ‘Any seeds that have not swelled up or softened after this can be chipped to increase their chance of germination.’

‘Chipping’ involves removing part of the outer shell of the seeds, which should be done carefully with a knife. When you come to the sowing, add some mulch to the soil to help the seeds retain moisture and nutrients, which will help speed up the germination process.