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in Garden· Growing a Cut Flower Garden Series· Spring· Tips and Tutorials· Winter

How to Grow Sweet Peas From Seed Indoors

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Have you dreamed of having a garden full of good old-fashioned sweet peas? I’ll share my tips on sowing sweet pea seeds indoors, how to transplant them into the garden, and much more.

sweet peas in cut flower garden

Sweet Peas Lathyrus odoratus

  • Annual hardiness zones 7 up
  • 6 hours morning sun
  • Well-draining soil

There are so many reasons I love growing sweet peas year after year…

sweet peas in the cutting garden

Vibrant Colors and Abundant Varieties

When you grow your sweet peas from seed, you have an abundant amount of colors and mixes available to choose from. The biggest challenge will be trying to decide which sweet peas you’re going to grow in your garden every year.

As an Amazon Associate, I earn from qualifying purchases. Affiliate links are used for your convenience. Read my full disclosure here.

Note: I am not a Master Gardener, but a self-taught hobby gardener who shares my opinions and what has worked for me in the garden.


sweet peas

The Sweet Smell of Every Bloom

I don’t know about you, but sweet peas are my favorite scented flower. This is one of those times when I wish there was such a thing as a “scratch and sniff” blog post, where you could take in the most incredible fragrance that comes from these beautiful blooms. The open-pollinated heirloom varieties are best known for their amazing fragrance.


sweet peas in glass jars

The Perfect Cutting Flower

With their stunning colors and long straight stems, sweet peas are the perfect cut flower for any late spring or early summer bouquet.


Windsor sweet peas

When to Grow Sweet Peas

In the warmer regions where winter weather is milder (zone 7 and above), sweet peas can be sown in the fall. For everyone else, you’ll sow your sweet pea seeds in late winter or early spring. They like cool roots and temperatures and can be sown indoors 10-12 weeks before the last frost of the season, which for my area is around April 18th.

Sweet peas can also be sown directly in the ground as soon as the soil can be worked in the spring. The optimum soil temperature for sowing sweet pea seeds is 55-65°F. Make sure to watch for birds, snails, slugs, and other pests, they love sweet peas!

Note: Sweet pea seeds are poisonous if ingested. Use caution around children and pets.


supplies to start sweet pea seeds indoors

Supplies to Sow Seeds

  • Sweet Pea Seeds
  • Seed Starter Potting Mix
  • Containers (that will accomodate deep roots)
  • Drainage Tray
  • Plastic Dome Lid
  • Labels

sweet pea seeds soaking in water

Steps for Sowing Sweet Peas

Step 1 – Soak Seeds in Water

In order to speed up the sprouting process by a few days, soak the seeds in water for 24 hours before sowing to soften the seed coat. This process can be done for indoor and spring sowing. There’s no need for fall sowing though.


Step 2 – Choose Container

Sweet peas produce an abundant amount of roots, so use the deepest pots you can find. I usually use 4-inch pots, or you can use root trainers as well. The more room you give the roots at the beginning stages of the seed starting process, the better the plant will grow in the long run.


container filled with seed starting mix

Step 3 – Fill Containers with Soil

I would recommend using a good quality seed starting potting soil when sowing your sweet pea seeds. Good soil will make all the difference in the world. The soil should be moistened before adding it to the container.

BENEFITS TO USING A SEED STARTING MIX

  • Helps to germinate quickly
  • Holds the moisture
  • Allows the roots to penetrate down into the garden soil quickly.

You can make the mix go even further by filling the bottom half of the container with regular potting soil and then filling the rest of it with the seed starting mix, where the seeds are going to be placed.


soaked sweet pea seeds

Step 4 – Sowing the Seeds

Sow 2 seeds per container or cell by creating a 1-half-inch hole into the soil, in 2 opposite corners. You can use a pencil, dibbler, or even your finger to make a hole.


container filled with seed starting mix and labels with tray filled with water

Step 5 – Bottom Water

Bottom watering is the most gentle and easy way to water your sweet pea seedlings. Fill the drainage tray with about an inch of water and let the container sit in the tray to evenly moisten the soil. DO NOT leave the container in a tray full of water for more than an hour.


seeds growing on heat pad and covered with plastic dome

Step 6 – Cover

Covering your container with a plastic dome lid will increase the humidity and speed up the germination process.

Place in a cool greenhouse or in a bright window in the house.


sweet pea seedlings growing indoors

Once the Sweet Peas Have Germinated

Uncover the Container

Take the plastic lid off the container once the seeds have germinated.


sweet pea seedlings growing indoors

Pinching

Once the sweet pea plant is 4-6 inches tall and has at least 3 sets of leaves on each stalk, start pinching it back to encourage side shoots. Pinching not only encourages the plant to actively branch from the base, but also produces more blooms. Snip off the central growing tips just above leaf joints and continue this throughout the growing season.

planting seedlings in cut flower garden

Preparing the Garden Beds

When planning the location of your garden beds, keep in mind that sweet peas love the full sun in the northern half of the US, and afternoon shade in the southern states.

Provide Nutrients

Sweet peas are heavy feeders and need extra nutrients. When preparing the garden beds for transplanting, add a layer of compost or bone meal, and natural fertilizer. Mix these ingredients deep into the soil.

You can read more about preparing your garden for seedlings HERE.


sweet peas growing on the trellis

Provide a Structure for Sweet Peas to Climb

Sweet pea vines will grow quickly and at least 6 feet tall, so they’ll need a strong structure to climb on. Setting up a structure, like a trellis, before the sweet pea vines start growing, will not only be easier but will less likely damage your plants.

sweet peas in color combination

Tall wooden or metal posts with metal fencing attached will allow the vines to climb up them. I use cattle fencing or chicken wire.

As the sweet peas continue to grow up the trellis through the season, tie the vines to the structure. I use twine. They can grow more than a foot a week during the prime growing season.


sweet pea seedling

Transplanting Sweet Pea Seedlings to the Garden

Transplant the sweet pea seed starts to garden beds around the last spring frost. Plant in two rows, one on each side of the trellis, spacing roughly 8 inches apart, down the row.

sweet pea seedlings growing on trellis

Watering

Sweet peas need a lot of water to thrive, especially during warm weather. I set up soaker hoses as soon as they’ve been transplanted to their new home in the garden.


sweet peas in cut flower garden

Feeding Plants

Feed plants weekly with diluted fish and seaweed emulsion.


Caring for Your Sweet Peas

To prolong blooming, harvest and deadhead flowers frequently to keep the plants from setting seed. Deadheading is the process of trimming back the old flowers, encouraging new growth.


sweet peas in clear jar

Harvesting

For the longest vase life, pick when there are at least 2 unopened flowers at the tip of a stem. Sweet peas are a short-lived cut flower, and will usually last only 4-5 days in a vase. Add a flower preservative to the water to extend vase life.


purple sweet peas

The most common mistakes made when growing sweet peas

  • Forgetting to add support at the time of planting outdoors. It’s difficult to add support after the sweet peas have already started to grow.
  • Not adding compost or fertilizer to garden beds with poor soil. This will result in less bloom production and weaker plants.
  • Planting too close together without thinning them. This can create powdery mildew and crowding, which reduces the plants flower production.
  • Waiting too late to plant them. Sweet peas don’t like the heat and won’t produce as many flowers.

sees starts under a plastic dome cover

Sowing Seeds Without a Greenhouse

You don’t have to have a greenhouse to sow seeds. My friend Stacy at Bricks ‘n Blooms shares everything you need to know about sowing seeds indoors. Make sure you visit her blog post for more!


Have you grown sweet peas in the garden? I’d love to hear from you in the comments below.

Until next time,

Happy Gardening!


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More Cut Flower Garden Posts You May Enjoy...

How to Harden Off Your Seedlings and Plants

How to Prepare Your Cut Flower Garden Beds

Step-by-Step Tutorial on the Seed Sowing Process

Seed Starting 101 - Growing a Cut Flower Garden Series

Planning Your Cut Flower Garden

The Cut Flower Garden Series


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Filed Under: Garden, Growing a Cut Flower Garden Series, Spring, Tips and Tutorials, Winter Tagged With: all about sweet peas, growing sweet peas, sowing sweet pea seeds

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Comments

  1. Renae says

    02/13/2021 at 5:48 am

    Seeing pics of your beautiful garden always amazes me. You are so talented. I love sweet peas! My grandpa’s yard was covered in them. I will be growing sweet peas from seed this year and I can’t wait to see them in bloom

    Reply
    • Kim says

      02/14/2021 at 2:52 pm

      Thank you for the amazing compliment! Everyone I talk to about sweet peas has a great memory about this flower or had a family member who grew it when they were younger.

      Reply
    • fred and sue groth says

      01/30/2022 at 2:56 pm

      Hi just a question my neighbor had sweet peas and they migrated to my garden. They have been choking out my flowers and I can’t get rid of them. I think they would be fine somewhere, where there are no others flowers to compete with the garden space. Maybe I’m doing something wrong. They have deep creeping roots. What do you think?

      Reply
      • Kim says

        01/30/2022 at 8:05 pm

        Thanks for your question. I have always grown sweet peas in containers and have never grown them in the ground. Plus they are annuals where we live so they die off every year. But yes, they have really deep roots and I can see that happening. Hopefully, you have a nice neighbor who will look at growing these flowers in a container to help you out.

        Reply
  2. Rachel Harper says

    02/11/2021 at 1:44 pm

    Kim
    I love your attention to detail. I’m sharing this on Dirt Road Adventures this weekend. Thanks for all the tips.

    Reply
    • Kim says

      02/14/2021 at 1:58 pm

      Thank you so much Racel for sharing my link. I really appreciate it!

      Reply
  3. Dawn says

    02/09/2021 at 9:59 pm

    Please tell us about the raised garden beds 😊

    Reply
    • Kim says

      02/14/2021 at 1:57 pm

      I will share about my raised beds this coming week in a FAQ blog post. Thank you for your interest!

      Reply

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Hi! I'm Kim. My blog, Shiplap and Shells is about my home, garden, and our Pacific Northwest lifestyle.
I live in a small beach cottage on the Puget Sound with my husband and sweet pups, Lucy, Jax, and Ollie. We have spent the last 9 years, renovating, reinventing, and adding character and charm to our 101-year-old home. Read More…

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