When To Plant Sweet Peas

Knowing when to plant sweet peas is the single most important factor for success with these beautiful flowers. Get the timing right, and you’ll be rewarded with a stunning, fragrant display that makes your spring garden truly vibrant.

This guide gives you the clear, simple steps you need. We’ll cover the best planting dates for different climates, how to prepare your seeds, and the care they need to thrive. Let’s get your sweet peas off to the perfect start.

The ideal time to plant sweet peas depends heavily on your local winter climate. These cool-season flowers can handle frost, but they don’t like intense summer heat. The goal is to get them established while the weather is cool so they bloom before the heat arrives.

For Mild Winter Climates (Zones 8-10)

If your winters are mild with few hard freezes, you can plant sweet peas in the fall. This is often the best method for a long, early bloom period.

Plant seeds directly outdoors from late October through November.
The seeds will sprout and grow slowly over the winter.
They develop strong root systems and are ready to explode with growth in early spring.

For Cold Winter Climates (Zones 2-7)

In areas with cold, freezing winters, you need to start seeds indoors in late winter. This gives them a head start for spring planting.

Sow seeds indoors 6-8 weeks before your last expected spring frost date.
This is typically sometime in February or early March.
You can also sow seeds directly outdoors as soon as the soil can be worked in early spring, but blooming will be later.

General Spring Planting Rule

Whether you started them indoors or not, sweet pea seedlings can be transplanted or seeds sown directly outside 4 to 6 weeks before your last frost date. The soil should be cool, not frozen and not yet warmed by summer.

Understanding Your Last Frost Date

Your average last spring frost date is your key calendar marker. You can find this with a quick online search for your town or zip code. Once you have that date, count backwards to schedule your seed starting.

How to Plant Sweet Peas for Success

Sweet peas have a few special needs at planting time. Following these steps will greatly improve your germination rates and seedling health.

Step 1: Seed Preparation

Sweet pea seeds have a hard outer coat. To help them absorb water and sprout faster, you should nick or soak them.

Nicking: Use a nail clipper or file to gently nick a tiny piece off the seed coat, being careful not to damage the inner part.
Soaking: Soak the seeds in room-temperature water for 12-24 hours before planting. You’ll see them swell up.
You can do both for the best results, but either method is effective on it’s own.

Step 2: Choosing the Right Location

Sweet peas need plenty of sun and good soil to perform their best.

Sunlight: Choose a spot that gets at least 6 hours of full sun each day. More is better in cooler climates.
Soil: They prefer rich, well-draining soil that stays moist. They are heavy feeders.
Support: Have your trellis, netting, or obelisk installed before you plant. Disturbing the roots later can set them back.

Step 3: Planting Seeds or Seedlings

Direct Sowing Outdoors:

Prepare the soil by mixing in several inches of compost or well-rotted manure.
Sow seeds 1 inch deep and 2-3 inches apart.
Water the area gently but thoroughly.
Seedlings should emerge in 10-21 days, depending on soil temperature.

Transplanting Indoor Starts:

Harden off seedlings for 7-10 days by gradually exposing them to outdoor conditions.
Plant them at the same depth they were in their pots, spacing them 6 inches apart.
Water them in well to settle the soil around the roots.
Gently tie the initial tendrils to your support to guide them.

Caring for Your Sweet Peas

Consistent care after planting ensures strong vines and an abundance of flowers.

Watering and Feeding

Sweet peas need regular moisture, especially once they start flowering. Don’t let the soil dry out completely.

Water deeply at the base of the plants once or twice a week, more often in hot, dry weather.
Apply a balanced, liquid fertilizer every 2-3 weeks, or use a slow-release granular fertilizer at planting time.
A mulch of compost helps retain soil moisture and suppresses weeds.

Pinching and Deadheading

These two simple techniques make a huge difference in your harvest.

Pinching: When seedlings are 4-6 inches tall, pinch off the top set of leaves. This encourages the plant to send up multiple strong stems, resulting in a bushier plant with more flowers.
Deadheading: Pick flowers for bouquets every day or two. If you leave the spent flowers on the vine, they will form seed pods, and the plant will think its job is done and stop blooming. Regular cutting is the secret to months of flowers.

Troubleshooting Common Problems

Even with good care, you might encounter a few issues. Here’s how to handle them.

Poor Germination

If your seeds don’t sprout, it’s usually due to old seeds, hard soil crust, or pests.

Always nick or soak fresh seeds from a reputable source.
Keep the soil consistently moist but not soggy until germination.
Mice and birds sometimes dig up seeds; covering the row with netting can help.

Yellowing Leaves

Yellow leaves can signal a few different problems.

Lower leaves naturally yellow as the plant grows; just pick them off.
Widespread yellowing often means the plant is hungry or the soil is too wet. Apply a fertilizer and check your drainage.

Lack of Flowers

If you have lots of leaves but few blooms, the cause is usually environmental.

Too much nitrogen: This promotes leafy growth. Switch to a fertilizer higher in phosphorus (the middle number on the package).
Heat: Sweet peas naturally slow down and die back as summer heat arrives. This is normal. An early fall planting can avoid this in mild climates.
Not enough sun: They simply won’t bloom well in deep shade.

FAQ: Your Sweet Pea Questions Answered

Can I plant sweet peas in summer?

No, sweet peas are cool-season plants. Summer heat will cause them to stop growing and die. For a vibrant spring garden, timing your planting for late fall or early spring is essential.

How early can you plant sweet peas?

In cold climates, you can start seeds indoors 6-8 weeks before the last frost. Outdoors, you can sow seeds as soon as the soil is no longer frozen and can be worked, which is often 4-6 weeks before the last frost.

Do sweet peas come back every year?

Most common sweet peas are annuals, meaning they complete their life cycle in one season. There are a few perennial sweet pea species (Lathyrus latifolius), but they are not fragrant like the annual types. For the classic fragrant blooms, you need to replant each year.

What is the best month to plant sweet peas?

For most gardeners, the best months are:

October-November: For fall planting in mild-winter areas.
February-March: For indoor seed starting in cold-winter areas.
March-April: For direct outdoor sowing in spring once the soil is workable.

Why are my sweet peas so short?

Short plants are usually due to late planting. If they experience warm weather and long days too soon after sprouting, they won’t grow tall vines before initiating flowers. Getting them in the ground early, while days are still short and cool, is key for long stems.

Getting the timing right for when to plant sweet peas sets the foundation for everything that follows. By sowing at the correct time for your region and providing consistent care, you’ll fill your garden with color and fragrance. Remember to pinch those seedlings, keep picking the flowers, and enjoy the beautiful results of your well-timed effort.