How to Grow Sweet Peas From Seed
Growing Sweet Peas is relatively easy and will reward you with bouquet after bouquet of blooms to fill your house or give you a lovely 'wall' of color and scent if you grow them for garden decoration.
Knowing when to plant sweet peas is important for success. Sweet peas will bloom profusely with wonderful flowers when started so that they have a long growing time in cooler weather as this helps to build a strong root system. A general rule is to plant sweet peas 6-8 weeks BEFORE your last frost date (you can find when your last frost date is here). However, in Zones 7-8 and above, you should start your sweet pea seeds in the autumn (find out your growing zone here).
Find out when to start sweet peas in your area by signing up to receive my sweet pea Seed Starting Planner.
My advice is to try growing sweet peas this year, and then grow them again next year (and all the years after – they are addictive!) and you will find a way to grow them that suits you and the area you live in.
Basic Growing Directions
Sweet pea seeds
Fresh potting mix
Well rotted manure
Trellis (or some other support for the sweet pea vines)
4” pots or Deep Rootrainers
- Fill your pots with potting soil and moisten thoroughly. I find it easier to pre-moisten potting mix by placing it in a bucket, adding water and mixing with a stick and then placing it into pots. Add enough water to make the potting soil feel like a wrung out sponge.
- Press the potting mix lightly into the pots.
- Use a pencil to create 2 holes in the potting mix and place 1 seed in each hole. The seed needs to be covered by no more that 1/4” - 1/2", so don't poke the holes too deep.
- Place a plant marker in your pot with the name of the sweet pea variety.
- Place your pots on a bright (but not hot) windowsill and let the seeds germinate. You should see shoots within 2 weeks or less. There is no need to water again until you see signs of germination.
- Once you see the first green shoot, move your pots to a bright location (an unheated greenhouse or cold frame would work depending on your location and temperatures).
- When your sweet pea plant has reached about 4-6 inches in height, it's time to plant it outside.
- Plant your sweet peas where they will receive full sun, be protected from strong winds and in free-draining soil.
- Dig a hole for your sweet pea and add the well rotted manure - mix it in with your soil. Remove the sweet pea from the pot and plant in the ground at the base of your trellis or other support.
- Water it in using the rose on your watering can or light spray from a hose.
- Protect from slugs, snails and birds.
- As the plant grows you will need to 'tie it in'. Simply use twine or some other garden string to secure the vine to your trellis.
- Cut flowers regularly as they fade to keep the blooms coming.
Choose Your Pot
The deeper the pot, the longer you can wait before planting out your sweet peas. The middle pot is a 4" pot - usually available from a good garden store.
To Soak or Not to Soak?
Some sweet pea experts advise soaking the seeds before planting. Other experts say that this is not necessary or can lower the germination rate. I conducted a small test to see whether or not I should soak my sweet pea seeds.
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Do they like being transplanted? I have tried this before and they kinda wilt after I put them in the ground outside.
Sweet peas don't mind being transplanted at all and I have never had problems with it.
Well, I’ve planted about 100 seeds so far. The SPG seeds I only planted 1 to a cell. Right now they are in my garden shed where the temp is 41 degrees. So should I bring them in to my kitchen table? My grandmother used to just put them in the ground the first of February. I’m zone 7. What to do?
Sweet pea seeds germinate at about 55F so you will need to move them where it is a little warmer. Once they have germinated move them outside where they will receive light - they will thrive outside at 41F. You can put them in the ground when they are about 5 inches tall.
Tulsa ok 74137. Zone 6.
In zone 6 you are best to start sweet pea seeds in late winter / early spring.
I live in zip code area 79601. When should I plant them. And can they be kept in pots always.
That's zone 8, so you can start your sweet pea seeds in the autumn. You can grow them in pots - just use pots that are 18 inches or taller and put canes in (I use 8ft canes pushed securely into the pots) for the sweet peas to scramble up.
I love sweet peas although have never grown them. I grow Morning Glories every year though and love them. I live in Alabama...when do I plant them?
Send me your zip code and I will let you know a good time to start sweet pea seeds.
I LOVE SWEET PEAS!!!
When should you plant if you live in zone 9 along the Texas Gulf Coast? I can remember as a child, my grandfather growing beautiful sweet peas. I have never had any luck growing them.
In Zone 9 you can start your seed now (in the autumn) and plant them out when they reach about 5 inches tall. Good luck!
I soaked for more than 24 hr. can I hold off planting for a day? Should I knick them now while wet? Did I ruin them?
You can try planting them and see what happens.. I've found that soaking seeds is unnecessary, but if you do soak them letting them sit in water for more than 24 hours is way longer than you need. You can try nicking them, but again, I've found that this is really unnecessary. Once the seed is soaked you should plant it straight away - don't let it dry out. Good luck!
How fortunate you are to live in Sebastopol! It’s one of my happy places.
Which sweet pea varieties grow the longest stems? Mine this year kept growing shorter and shorter stems making it difficult to create bouquets. (I didn’t get my seeds from you for this years crop; so that could be the problem.)
Sebastopol is a great place and such a great temperate climate that you can grow almost anything here :)
Many of the varieties I grow have long stems and are suitable for bouquet making, but as the season progresses, sweet pea stem length will get shorter and shorter. You can try adding blood meal to your plants to improve stem length as the season progresses. Also, planting sweet peas early will mean that they have a bigger root system which can also help the plants produce longer stems. Not sure where you are located, but you can also email me and I will try to help you figure out the best time to plant for your particular area.
What do you mean by panting in the fall for zones 7 & 8. Is this direct sowing into the ground or what?
" in Zones 7-8 and above, you should start your sweet pea seeds in the autumn " - means starting them in pots.
I was wondering how your test on soaking or not soaking sweet pea seeds turned out....
It went well - you can find out here if soaking or not soaking sweet pea seeds is necessary.
Can I plant my seeds in the fall directly on the ground? I live I'm Atlanta Ga
You can, but I don't do it because of the losses of seedlings to slugs/snails, birds and maybe even mice. Best practice is to start them in pots and transplant when they are about 4-5 inches tall.
Sun, shade, partial?
How far apart do different varieties (in the same family) have to be planted so they do not cross pollinate? (First time grower here, in cotati)
Lathyrus odoratus pollinate themselves about a couple of days before the flowers open, so it is very difficult for them to cross pollinate.