How to Grow Sweet Peas

The first time I really noticed sweet peas was at Butchart Gardens in British Columbia. I loved the flowers, but it was the fragrance that made me want to grow them in my own garden.

Now they’re one of my favorite cool-season flowers. In the low desert, timing is key. Sweet peas need cool weather to grow and bloom well, so planting early gives them the longest possible season before spring heat arrives.

They also need something to climb, consistent water, and regular picking once they start blooming. Here are five things that make the biggest difference when growing sweet peas.

1. Timing is Key: Plant Sweet Peas Early

Sweet peas are cool-season flowers. Give them plenty of time to grow before warm weather arrives.

In cooler climates, sow them in late winter or early spring as soon as conditions allow. In mild-winter climates (like ours in Arizona), fall planting gives the plants a head start and often results in earlier blooms.

Arizona Low Desert Planting Dates

• Start seeds indoors: September through January
• Plant seeds or transplants outside: October through February

In the low desert, I prefer planting toward the earlier part of the window—once soil temperatures range from 50-60ºF (10-15ºC). Earlier planting gives roots and vines more time to develop and usually results in a longer bloom season before spring temperatures climb.

If you’re planting toward the end of the window, choose a location with morning sun and some afternoon shade. That can help extend flowering as temperatures rise.

Sweet peas generally begin blooming in late winter or early spring and continue until heat ends the season. Sweet peas and poppies bloom during the same cool-season window in my garden. Learn how to grow poppies here.

2. Pick the Perfect Sweet Pea Variety for Your Garden

Sweet peas come in different heights, colors, fragrances, and bloom times. Some varieties also perform better under different day lengths, so choosing a variety suited to your climate can make a difference.

For more help choosing varieties, see my complete guide to sweet pea varieties.

3. How to Plant and Care for Sweet Peas

Sunlight

Sweet peas grow and flower best with plenty of light. In cooler climates, full sun is usually ideal. In Arizona’s low desert and other hot-summer climates, morning sun with afternoon shade can help extend the bloom season.

Soil

Plant sweet peas in fertile, well-drained soil. Before planting, add compost if your soil needs organic matter. They don’t like constantly soggy soil, but they also don’t flower well if the soil repeatedly dries out.

Planting

• Sow seeds about 1 inch (2.5 cm) deep
• Space seeds 2 to 3 inches (5 to 7.5 cm) apart
• For square-foot gardening, plant 4 sweet peas per square.

Once seedlings are growing well, thin them if necessary, so they have enough room and airflow. Sweet peas develop substantial root systems, so if you’re growing them in containers, choose a container at least 12 inches (30 cm) deep.

Watering

Keep the soil consistently moist but not waterlogged. Water deeply rather than giving plants frequent shallow sprinkles. Mulch helps hold moisture in the soil and becomes especially useful as spring temperatures rise.

Feeding

If you start with healthy soil and compost, sweet peas don’t need constant fertilizing. Plants grown in containers may benefit from supplemental feeding because nutrients wash out faster. If growth or flowering slows, use a balanced or bloom fertilizer as directed on the label. Avoid overdoing nitrogen, which can encourage lots of leafy growth.

Pests and Problems

Aphids, slugs, snails, and powdery mildew are common sweet pea problems.

Before treating aphids, look for ladybugs, lacewings, hoverflies, and other beneficial insects that may already be feeding on them.

Give plants enough room for airflow, and avoid repeatedly wetting the foliage to help reduce powdery mildew.

Pinching Sweet Peas

Pinching is optional, but it can encourage branching. When young plants have several sets of leaves and are growing well, pinch out the growing tip just above a set of leaves. This encourages side shoots and can produce a fuller plant. Fall-planted sweet peas sometimes branch naturally, so don’t feel like you have to pinch every plant.

4. Support Your Sweet Peas as They Grow

Most sweet pea varieties are climbers and need support. If possible, install the trellis or support before planting. That way, you won’t disturb established roots later. Young vines may need a little help finding the support at first. Once their tendrils grab hold, they usually climb on their own.

Good Support Options

• Trellis: A simple trellis works well and makes flowers easy to see and cut.
• Arches: Sweet peas look beautiful trained over an arch.
• Fences: Chain-link and other open fencing make easy supports.
• Obelisks: A good option for raised beds and containers.
• Containers: Shorter varieties can also grow in containers with a small trellis or obelisk.

Most climbing varieties can grow 6 feet (1.8 m) or taller, so give them enough vertical space.

5. Keep Sweet Peas Blooming as Long as Possible

Once sweet peas begin flowering, regular harvesting is one of the best ways to keep them blooming.

• Pick Flowers Often: Cut flowers frequently and remove faded blooms before seed pods develop. Once the plant begins putting energy into mature seeds, flower production slows.
• Keep the Soil Moist: Sweet peas don’t handle dry soil well, especially as temperatures warm. Check the soil regularly and water deeply when needed.
• Mulch the Roots: A layer of organic mulch helps hold moisture and keeps the root zone cooler as spring approaches.
• Keep Plants Supported: Guide loose vines back onto the trellis as they grow. Good support keeps plants from collapsing into a tangled mass and makes harvesting easier.
• Understand When the Season is Over: In the low desert, sweet pea season eventually ends because of heat. When temperatures rise and plants begin declining, don’t assume you’ve done something wrong. Sweet peas are cool-season flowers, and eventually our spring temperatures become too warm for them.

Harvesting Sweet Peas for Cut Flowers

Sweet peas are some of my favorite flowers to bring inside because their fragrance fills a room. Here’s how to get the best out of your cut flowers:

• Cut in the morning when stems are well hydrated.
• Choose stems with several open flowers and additional buds showing color.
• Use clean scissors or pruners and cut the stem.
• Place stems in water immediately.
• Remove flowers as they fade.

Sweet peas typically last around 5 to 7 days in a vase. Floral preservatives can help extend vase life. If you’re growing sweet peas specifically for bouquets, choose varieties bred for longer stems and larger flowers.

To save seeds, leave a few flowers on the plant near the end of the season and let the pods fully mature. Remember that saved seed from hybrids may not produce plants identical to the parent. For more information on saving seeds for next season, read this guide.

Sweet Pea FAQs

Plant sweet peas early, give them something to climb, and keep picking the flowers once they begin blooming. In the low desert, the season doesn’t last forever, but that makes the weeks when they’re covered in fragrant flowers even better.