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Back to Dirt Farm’s Guide to Growing Sweet Peas

Picture this…

You step outside into the garden. A soft breeze blows and there is a distinct floral sweetness in the air. I bet the first thing that comes to mind is the smell of a rose or maybe honeysuckle or lavender. Let's add another wonderful flower to the list called a sweet pea. Sweet peas are climbing vines that produce loads of beautiful, fragrant flowers. They make a wonderful addition to your garden and are super easy to grow. They come in a wide variety of colors and fun pattern types too!

But I don’t have a green thumb!

I am going to give you a little secret. As long as you give them plenty of compost and the right temperature, they pretty much take care of themselves. So let’s start at the soil. Sweet peas are considered heavy feeders so it is a good idea to give them high quality compost each season. If you don’t have the greatest soil, you can also give them fish emulsion and compost tea throughout the growing season if you see them struggling.

As they grow, you will need to tie them to the trellis if you want them to grow up, not out. Depending on the variety, the trellis will need to be anywhere from 4ft to 8ft but it is better to go taller than shorter. Towards the end of the season, they will start to set seed and you can let the pods turn brown then harvest the seeds to plant the next year. Store the seeds in the fridge for 1-2 seasons or the freezer for longer storage times.

The Nitty Gritty

Sweet peas are frost tolerant when seedlings and prefer temperatures below 80. If watered well to keep them cool, they can survive short stents up to the 90s just fine. Typically you will plant the seedling outside when there is a chance of light frost but no snow! Here in the PNW, we start them indoors in March and move them outside the first week of April (April 15th is our last frost date).

As for the seeds, there is a debate on whether to soak or not to soak. Personally, I suggest not to soak. You can nick a little bit of the seed coat off with your fingernail but most of the time it is not necessary. To sow, place the seed about ½” down and cover with dirt so that there is no light. Moisten the soil but do not soak and keep the soil moist until germination occurs. It is important not to keep the soil too wet or the seeds will rot. I tend to lightly water once every day or two.The seed germinates best when kept in a warm room(think kitchen counter temperature) but will germinate just fine but slower at lower temperatures. You should see the stem poke up about a week or two after sowing inside. Once the seedlings ‘pop’ out,put them under a light source and move them into a lower temperature area (ideally between 55-62F). This will encourage the plants to grow slow and strong. If you notice the plants getting leggy, make sure the light source is strong/ close enough and the temperature isn’t too high. When your little baby plants have 3-4 sets of leaves, cut or “pinch” the top 1-2 sets of leaves off to encourage branching. If you sowed the seeds outdoors, the cold weather should naturally pinch the plant for you. If you started the plants indoors, harden them off after pinching before transplanting.

Hardening Off

Start incrementally. Set them outside in the shade for a few hours in the afternoon for the first few days. Gradually increase the amount of time outside each day and start placing them in the sun. When the plants are hardened, put the pots in the area you plan to permanently place the peas for a couple days before transplanting. Now, if you are forgetful like me, you can do the ‘cheater’ way of hardening. This method is to put in the shade all day for the first two days. In the shade all day and night for the rest of the week. And move to the sun after the first week. This is a more abrupt way to harden but way less stressful to the gardener. Either way, just watch the plants and if they look sickly, give them some care.


Space the plants about 6 inches apart down the trellis. You can plant on both sides if you stagger them. It is important not to plant too densely to avoid disease later in the life cycle of the plant. Crowding can lead to mold and fungal development.

Other Stuff

Sweet peas love the sun but can benefit from afternoon shade. They need at least 6 hrs of sunshine a day. Water regularly so that the top 2 inches of soil is wet and let them dry out slightly between waterings. I tend to water 2-3 times a week when the temperature is cooler and daily when summer really hits.

Pests: Here in the PNW we have aphids and deer. For the deer, the best thing to do is to put up a fence. They like to nibble the new growth and flowers off. As for the aphids, it's a constant battle. When you first notice these little green pests, dust the vines with diatomaceous earth. This is ground up powder of fossil which will cut the aphids and cause them to dehydrate and die. If this doesn’t work, you can spray with neem oil each day until the aphids are gone.

The hardest part of growing flowers is waiting

Once the plants are outside on their trellis, it's time to wait and see. Keep watering them and in no time they will begin to shoot up so quickly. I swear it seems like they grow a foot a week once summer hits. When the plant senses enough sunlight hours, they will start to bloom. Once the flowers start, it's time to cut cut cut! The more you cut, the more they grow. So harvest, bring them inside and share them with friends. It is best to cut when the top two flowers are still closed. Once harvested, the flowers will last up to 5 days inside if given fresh water daily, flower food and a cool room. Towards the end of the season, let them set seeds. Feel free to share and save the seed to plant the next season. No one can ever have too many sweet peas in their life.


I cannot seem to find the answer to this question. How many seeds per packet?


I live in the Spokane Valley. As you can imagine we get snow. I’ve had success with winter sowing and was wondering what is your suggestion for winter sowing sweet peas?

Also, is using bone meal in the planting soil advantageous for the sweet peas?

Continued success.


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