Have you dreamed of having a garden full of good old-fashioned sweet pea flowers? I’ll share my tips on sowing sweet pea seeds indoors, transplanting them into the garden, and caring for these beautiful blooms throughout their growing season.
I have grown sweet peas in my cut flower garden for years and love them more every year. This post will show you how to grow sweet peas from seed.
But if you’re planning on buying sweet pea starts at the nursery or local garden center, you’ll still get a lot out of this post. I’ll show you how to transplant the seedlings into the garden and grow healthy flowers.
Sweet Pea Basics
Sweet Peas Lathyrus odoratus
Generally, sweet peas bloom from late spring through early summer. They thrive in USDA hardiness zones 5-9, so if you live outside of these areas, it may not be possible for you to cultivate them successfully. With the right conditions, you’ll enjoy beautiful blooms all season long.
Sweet peas require at least 6 hours of morning sun and well-draining soil.
As an Amazon affiliate, I earn from qualifying purchases at no extra cost to you. My blog contains other affiliate links as well for your convenience. Click here to read my full disclosure policy.
I’m a self-taught hobby gardener, not a Master Gardener. Everything I share with you on my blog is my personal opinion and things that have worked for me.
Table of Contents
- Sweet Pea Basics
- Why You Should Grow Sweet Peas From Seed
- When to Grow Sweet Peas
- Supplies to Sow Seeds
- Steps for Sowing Sweet Peas
- Once the Sweet Peas Have Germinated
- Preparing the Garden Beds
- Grow On a Structure for Sweet Peas to Climb
- Hardening Off Your Sweet Peas
- Transplanting Sweet Pea Seedlings to the Garden
- Caring for Your Sweet Peas
- Harvesting Sweet Peas
- Common Mistakes Made When Growing Sweet Peas
- Sowing Seeds Without a Greenhouse
Why You Should Grow Sweet Peas From Seed
Fragrant sweet peas are easy to grow from seed and need minimal care. They grow best in cool climates with light shade and plenty of water.
These old-fashioned flowers are perfect for beginning gardeners. They grow quickly and reach full maturity within two months if planted at the right time.
Sweet Peas Offer Vibrant Colors and Abundant Varieties
With their bright colors and sweet scent, sweet peas make a great addition to any flower arrangement.
You have a wide range of colors and mixes available when growing your sweet peas from seed. The biggest challenge will be deciding which sweet pea plants you will grow in your garden every year.
I have planted 20 varieties since starting my cut flower garden and have loved every single one.
The Sweet Smell of Every Sweet Pea Bloom
Annual sweet peas have the most amazing and sweet fragrance. This is one of those times when I wish there were such a thing as a “scratch and sniff” blog post where you could take in the most incredible fragrance from these beautiful blooms.
The open-pollinated heirloom varieties are best known for their incredible fragrance.
Sweet Peas are The Perfect Cutting Flower
With their stunning colors and straight long stems, sweet peas are the perfect cut flower for any late spring or early summer bouquet.
Deer Resistant and Pollinator Friendly Blooms
Sweet peas are deer-resistant, but pollinators like butterflies and bees love them. This makes this plant the best of both worlds.
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.
These plants like cool temperatures and can be sown indoors 10-12 weeks before the last frost date of the season, which for my area is around April 18th. This information is also on the seed packets for your convenience.
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. 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 Sow Seeds
- Sweet Pea Seeds
- Seed Starter Potting Mix
- Containers (that will accommodate deep roots)
- Drainage Tray
- Plastic Dome Lid
Steps for Sowing Sweet Peas
Step 1 – Soak Seeds in Water
To speed up the sprouting process by a few days, soak the seeds in water for 24 hours before sowing to soften the hard seed coat. This process can be done for indoor and spring sowing. You can skip this process when fall sowing.
Step 2 – Choose a Container
Sweet peas produce abundant roots, so use a deep container when sowing seeds. I usually use 4-inch pots, but you can also use root trainers.
The more room you provide for their large root systems at the beginning stages of the seed-starting process, the better the plant will grow in the long run.
Step 3 – Fill Containers with Soil
I 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.
Fill your containers with moist soil. You always want well-drained soil and never saturated.
BENEFITS TO USING A SEED STARTING MIX
- It 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 with the seed starting mix, where the seeds will be placed.
Step 4 – Sowing the Seeds
Sow two 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.
Step 5 – Bottom Water
Bottom watering is the most gentle and easy way to water sweet pea seeds. Fill the drainage tray with about an inch of water and let the container sit in the tray to moisten the soil evenly.
DO NOT leave the container in a tray full of water for over an hour.
Step 6 – Cover With a Humidity Dome Lid
Covering your container with a plastic dome lid will increase the humidity and speed up the germination process.
Place in a cool greenhouse or a bright window in the house.
Once the Sweet Peas Have Germinated
Uncover the Container
Take the humidity dome lid off the container once the seeds have germinated.
Provide Good Air Circulation
You will need to make sure your seedlings get good air circulation, so having a fan in your indoor growing space will hugely benefit them.
When planting sweet pea seedlings indoors, it is important to provide the plants with adequate nutrients to promote healthy growth. An all-purpose liquid fertilizer should be applied to the soil every few weeks, according to the instructions on the fertilizer package.
Pinching Your Sweet Peas
Sweet pea pinching is essential in getting the most out of your plants.
Pinching is when you remove the central growing tip on each stem above the leaf joints. This not only encourages the plant to branch from the base to promote a bushier plant actively but also produces more blooms on each stem. It can also help prevent the plant from becoming “leggy.”
Once the sweet pea plant is 4-6 inches tall and has at least three sets of leaves on each stalk, start pinching it back to encourage side shoots. Continue this process even when they’re planted in the garden bed throughout the growing season.
Preparing the Garden Beds
Prepare Garden Beds in Full Sunlight
When planning the location of your garden beds, remember that sweet peas love the full sun in the northern half of the US and afternoon shade in the southern states.
They require full sunlight to grow and bloom, so they should be planted in an area with at least six hours of direct sun per day.
Sweet peas are heavy feeders and need extra nutrients. When preparing the garden beds for transplanting, add a layer of organic matter such as compost or bone meal and natural fertilizer. Mix these ingredients deep into the soil.
Make sure the soil has good drainage.
Grow On a Structure for Sweet Peas to Climb
Sweet pea vines will grow quickly to at least 6 feet tall, so they’ll need strong vertical support to climb on. If left unsupported, they can become top-heavy and fall over. This can cause broken stems and damaged flowers.
Setting up a structure, like a trellis, before the sweet pea vines start growing will be easier and less likely to damage your plants. Tall wooden or metal posts with metal fencing attached will allow the vines to climb. I use cattle fencing or chicken wire.
As the sweet peas grow up the trellis through the season, tie the vines to the structure. I use twine. During the prime growing season, they can grow more than a foot a week.
Hardening Off Your Sweet Peas
Before planting out your sweet peas, make sure they have been hardened off by gradually exposing them to outdoor conditions over a period of 7-10 days. This will help reduce any shock from being transplanted and ensure they grow strong and healthy once planted in their final location.
Transplanting Sweet Pea Seedlings to the Garden
Sweet pea seedlings can be translated to garden beds around the last spring frost. Be sure to plant in the early morning or late evening when temperatures are cooler and there’s less chance of wilting due to heat.
Plant in two rows, one on each side of the trellis, spacing roughly 8 inches apart, down the row.
Once your sweet peas have bloomed, it is important to ensure you provide them with the ideal environment to grow and thrive. Caring for sweet pea plants involves providing enough moisture, at least 6 hours of sun a day, and regular fertilizer applications.
Caring for Your Sweet Peas
Sweet peas need a lot of water to thrive, especially during warm weather.
Keep the soil evenly moist, but not waterlogged. Water deeply whenever the top inch of the soil feels dry. Avoid overhead watering to help prevent fungal diseases.
To provide enough moisture for your blooms, water deeply once a week during the growing season and mulch around the base to help retain moisture.
Fertilizers and seaweed emulsions are great for sweet peas. They need plenty of nitrogen to produce abundant blooms, and fertilizers or seaweed emulsion can provide the necessary nutrients.
The fertilizers will give a quick boost to plants while using seaweed emulsion over time can help create healthier soil that provides more sustained nutrition for your sweet pea plants.
Pest and Disease Control
Watch for common pests like aphids and slugs. Use natural and organic options if necessary. Look for signs of disease such as powdery mildew or root rot.
Deadhead and Harvest Regularly
To prolong blooming, harvest and deadhead flowers frequently to keep the plants from setting seed. Deadheading is trimming back the old flowers, encouraging new growth.
Harvesting Sweet Peas
For the longest vase life, pick sweet peas when there are at least two unopened flowers at the tip of a stem. Sweet peas are short-lived cut flowers and usually last only 4-5 days in a vase.
Add a flower preservative to the water to extend the vase’s life.
Save Seeds for Next Year’s Garden
You can save the seeds in each sweet pea seed pod to grow next year.
- Gather mature sweet pea pods from the plant.
- Choose pods that are firm, dry, and brown.
- Open the pods and shake the seeds into a bowl or container.
- Spread the seeds on a paper towel and let them dry for a few days.
- Place the dry seeds in an airtight container and store them in a cool, dry place.
- Plant the seeds next year for beautiful and fragrant blooms.
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 plant’s flower production.
- Waiting too late to plant them. Sweet peas don’t like the heat and won’t produce as many flowers.
Have you grown sweet peas in the garden? I’d love to hear from you in the comments below.
Until next time,
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!
Be sure to follow me @shiplapandshells on the following…