How To Grow And Care For Sweet Pea Flowers

It's no wonder age-old sweet peas are still a favorite Southern floral.

Fact checked by Khara Scheppmann

Ornamental sweet peas (Lathyrus odoratus) have been around for centuries, long enough to be considered old-fashioned, but these delicate-looking flowers are still popular. Sweet peas are climbing vines with curling tendrils and clusters of dainty flowers. Look for these cool-weather annuals in crimson, apricot, violet, rose, white, pink, blue, and other colors. Some gardeners think they smell like orange blossoms, honey, and jasmine. Others say they have a grape-like scent.

Let these fast-growing vines twine over an arbor, spill out window boxes, or delight as clippings in bouquets. Sweet peas are deer-resistant, but butterflies and bees love them. A similar plant, the perennial or everlasting pea (L. latifolius), is considered invasive in parts of North America, so be aware of what you are growing. You can differentiate between the two because L. latifolius does not have the sweet scent. If you live in USDA Zone 8 or warmer, plant them outdoors in rich, well-draining soil in late fall. Elsewhere, plant them from late winter to very early spring. All parts of sweet peas are toxic to horses and people, so don't plant them in pastures or anywhere near your vegetable garden. You wouldn't want to mistake the charming pods these cottage flowers produce for the real thing.

Sweet Pea Care

Sweet peas are annuals that like cool weather and typically fade away in the heat of summer. Plants are available for a very short window, so most gardeners plant seeds directly in the garden. Though you can start seeds indoors a few weeks before planting, twining plants can be challenging to move if you start too early.

Sweet peas can escape into roadsides and other areas, so it's a good idea to remove any pods that develop, which will also increase flowering. Support sweet peas in the garden with netting, twine, or anchored trellises so the fast-growing vines won't pull each other down.

Light

Sweet pea flowers thrive in full sunlight. In areas with hot, humid summers, sweet peas can benefit from light or dappled shade in the afternoon. To prolong this plant's life in the South and keep the vines from wilting, grow sweet peas in an area that provides enough afternoon shade.

Soil

Sweet peas need deep, well-draining, humus-rich soil with a neutral to alkaline pH. Dig a trench that is 12 inches deep and fill with a soil mixture that includes plenty of compost and organic matter. For best results, amend the soil with compost in the fall or at least a week before planting. Mulch around the base of plants to keep the soil moist and cool.

Water

Water regularly if rainfall isn't sufficient. Keep the soil lightly moist during the growing season. Check the top inch of soil with your fingers and water if dry.

Temperature and Humidity

Sweet pea seeds can be planted outdoors as soon as the soil can be worked. If you wait until after the last frost, your plants may not have enough time to mature before hot, humid temperatures set in. While the seedlings tolerate light frosts, heavy frosts can damage the foliage. If you have mild winters and rarely experience frost, you can plant the seeds in late fall for early spring blooms. Gardeners in cooler regions may enjoy flowers until mid-summer or even later.

Fertilizer

Building a deep, humus-rich soil should provide all the nutrients your sweet peas need to get a good start. If you want to encourage more flowering, use a fertilizer that is high in phosphorus and lower in nitrogen, such as tomato fertilizer. You can use liquid fertilizers weekly or every two weeks once the first bud appears; for slow-release granule fertilizers, follow package directions. Blood meal can also help to increase a sweet pea's length so that you can take cuttings, but too much nitrogen can reduce flowering.

Types of Sweet Peas

• 'Henry Eckford': This heirloom with orange-red salmon flowers dates to 1904.

• 'Old Spice': Choose this mix of colors for its honey and orange blossom perfume.

• 'Cupani's Original': Sweet peas like cool weather, but some tolerate more heat than others, like this purple and blue bicolor.

• 'Strawberry Sundae': Highly fragrant flowers in pastel pink, rose, and white.

• 'Flora Norton': These soft blue flowers are wonderful for cutting. Vines grow to six feet.

• 'Bijou Mix': These short, bushy sweet peas mix lavender, pink, purple, blue, and white.

• 'Sugar 'n Spice': Enjoy these solid and bicolored blooms held on dwarf plants in hanging baskets. At seven inches tall and wide, they don't need pinching.

• 'Cupid Pink': White and pink bicolored flowers bloom on this dwarf plant.

Pruning

Other than occasional pinching, sweet peas don't need much pruning. You can make the plant branch at the base and encourage bushier growth by pinching the plants when they are small. Once the seedlings reach 4 inches in height, pinch off the central growing tip with your fingers or flower snips just above a couple of leaf nodes.

Deadhead sweet pea flowers often and remove dead or diseased leaves and pea pods. Sweet pea vines die naturally when the temperatures rise. Pull and compost them if they're not diseased or infested with pests.

If your sweet pea plant grows too tall, cut off the top of the primary vine just above a shoot or bud.

Propagating Sweet Peas

Sweet peas can easily be propagated from cuttings in water or soil. For best results, take cuttings early before temperatures rise too much. Use young sweet pea seedlings, but wait until they have started to develop side shoots before taking cuttings. You can prune the growing tip to create a new plant while leaving the side shoots to develop bushy growth on the mother plant.

Here's how to root cuttings in water:

1. Use sharp scissors or floral snips to cut 3-5 inches of the stem, just above the side shoots that have started to develop on the vine.

2. Remove any leaves from the bottom of the cutting, making sure to leave a few leaves at the top. Optional: Dip the stems into a liquid rooting hormone solution for a few seconds.

3. Place cuttings in a container of fresh water, then set the container in bright, indirect light.

4. You should see new roots growing in about two weeks. Replace the water in the meantime if it starts to get cloudy.

5. Fill small, relatively deep containers with high-quality, humus-rich potting soil. Use a pencil to create planting holes, then stick the cuttings in so that the roots and first bare leaf node are beneath the soil.

6. Gently pack the soil around cuttings and water well. Move the container into partial sunlight (such as a little morning sun) and continue watering for about six weeks until the cuttings have more developed roots to transplant outside.

Alternatively, you can root cuttings directly in soil, following these steps:

1. Fill small, relatively deep containers with high-quality, humus-rich potting soil.

2. Use sharp scissors or floral snips to cut 4 or 5 inches of the stem, just above the side shoots that have started to develop on the mother vine.

3. Remove any leaves from the bottom of the cutting, making sure to leave a few leaves at the top. Dip the bottom of the stems into powdered rooting hormone.

4. Use a pencil to create planting holes, then stick the cuttings in so that two bare leaf nodes are beneath the soil.

5. Gently pack the soil around cuttings and water well. You can set the plants in a cool, humid greenhouse, or create your own greenhouse by covering the plants with a clear plastic dome or plastic wrap (use stakes to keep the plastic from coming into contact with the plants). Protect the cuttings from freezing temperatures, excessive heat, and excessive sunlight while they are getting established.

6. Continue watering for about six weeks or until the cuttings have developed enough roots to transplant outside.
   

How To Grow Sweet Peas From Seed

Indoors, sow sweet pea seeds four to six weeks before you intend to plant them out (about six to eight weeks before your last frost). Some seeds can take a long time to germinate, but two to three weeks is typical. Soak them overnight in water to soften their hard seed coats for better germination. Seeds that do not swell from the soaking will have a better chance if you nick the seed coating. Then plant two or three seeds per pot in biodegradable pots of fresh potting mix. Cover the containers with clear plastic bags to create mini-greenhouses and keep them in a cool, bright spot in your house. Seeds germinate best with a soil temperature of 55°-65° F.

When the seedlings are up, remove all but one in each pot. Two weeks before the last spring frost, transplant the pots directly into the garden or outdoor containers so you won't disturb the long tap roots. Pinch the growing tips when the seedlings are about 4 inches tall, so they'll form side shoots.

Plant them in rows, 6 to 8 inches apart, in full or partial sun. You should see blooms four to six weeks after the vines start growing.

Potting Sweet Peas

When grown in containers, sweet peas need something to climb like a small trellis. Choose short varieties so you won't need tall supports, and use containers at least 6 inches deep filled with good potting mix. Pinch the seedlings' growing tips when they're 4 inches tall. Otherwise, caring for sweet peas in containers is the same as caring for sweet peas in the garden, although you may need to water them more often.

Overwintering

While sweet peas are relatively cold-hardy, there are ways to protect plants during the winter. Move sweet peas indoors when temperatures drop below freezing when planted in containers. In the late winter, prune dead or diseased leaves and flowers to the ground to make room for new growth. To help protect the plant's roots, cover them with burlap.

Common Pests & Plant Diseases

Even before they sprout, sweet peas can become the victim of hungry rodents that dig up the seeds. Protective netting or wire baskets can help keep pests away until the seedlings emerge.

Pests like aphids, leaf miners, spider mites, and thrips can attack sweet peas. Slugs and snails also pose a risk to sweet peas. Try knocking off pests with a strong stream of water from your hose. Keep sweet peas weeded so pests can't hide nearby. When needed, spray with insecticidal soap or neem oil to eliminate pests. Use snail or slug baits or traps.

Possible diseases include downy mildew, leaf spot, rust, virus diseases, root and crown rot, and rust. Remove heavily infested or diseased foliage to keep problems from spreading. Help prevent diseases and rotting by giving plants good air circulation—water with drip irrigation or soaker hoses to keep foliage dry. If diseases persist, look for a fungicide labeled for your specific problem.

How To Get Sweet Peas To Bloom

During late spring and early summer, sweet peas bloom faster. Deadheading will encourage the plants to keep producing flowers. To help increase the flower's bloom size and longevity, use compost or dried aged manure. Fertilizers with higher phosphorus than nitrogen will also improve flower production. Sweet peas bloom best in full sun.

Common Problems With Sweet Peas

Sweet peas are easy to start from seed, but they can be finicky about soil and don't take well to being planted the wrong time of year. Time your planting to avoid heavy frosts and hot weather and provide deeply tilled, rich soil and consistent moisture for the best results. Here are a few problems you may run into when growing sweet peas.

Bud Drop

Sweet peas sometimes drop their buds when they get too dry or nighttime temperatures are too low. Water as needed to keep the soil moist. Cut off buds that threaten to drop at the base of their stems so the plants can keep growing. Overfertilizing can also cause bud drop. Stop feeding until the flowers open entirely.

Not Enough Buds

Too much nitrogen can promote leaves instead of flowers. Switch to a tomato fertilizer if your product seems to result in more green growth than blooms.

Yellow Leaves

Leaves can turn yellow from overwatering or overly heavy soil. Keep the soil lightly moist and improve drainage if possible. This problem can also happen if compost is not mature enough and ends up burning the roots.

When sweet peas grow leggy and a pale yellowish-green, this is a sign of insufficient light. Move your container or prune surrounding plants if possible to increase sun exposure.

Crispy Leaves

Sweet pea leaves will bleach and turn crisp when scorched by heat and sun. Increasing watering or providing some afternoon shade with screening could help. Crispy leaves can also indicate your plant is at the end of its life.

Frequently Asked Questions

What shouldn't you plant with sweet peas?

Sweet peas have a deep root system that doesn't like to be disturbed. Don't plant onions or potatoes or deep-rooted perennials next to sweet peas. Also, don't plant them near vegetables or anything edible, as you don't want to confuse the pods with food.

Do sweet peas reseed?

Sweet peas (Lathyrus odoratus) are an annual and only live one year, usually withering away from the heat of summer. However, if you allow your plants to set seed, new seedlings may emerge the following year.

What are some alternatives to sweet peas?

If you're looking for a more heat-tolerant, fragrant vine for the South, try woodbine honeysuckle (Lonicera periclymenum) or American wisteria (Wisteria frutescens).

For more Southern Living news, make sure to sign up for our newsletter!

Read the original article on Southern Living.