Sweetpea
Lathyrus odoratus · Guisante De Olor · Sweet PeaUSDA | Grow Zone
3-11Outdoors all year in zones 3 to 11. Anywhere colder, keep it as a houseplant. Protect it below 40°F.
- Light
- Full sun, 6-8 hours
- Water
- Deeply once a week
- Humidity
- 40-60% preferred
- Temperature
- 55-70°F (13-21°C)
- Difficulty
- Intermediate
- Growth
- Moderate
- Mature size
- 4-6 ft tall, 1-2 ft wide
Sweetpeas, or Lathyrus odoratus, are beloved for their fragrant blooms and vibrant colors. Native to the Mediterranean, they are popular in gardens for their climbing habit and ability to attract pollinators.
Ask Vesper about Sweetpea
Ideal temperature
55-70°F is where it grows fastest. Below 40°F cold damage starts.
Spacing and harvest
- Mature size
- 4-6 ft tall, 1-2 ft wide
- Plant apart
- 12-24 in
- Frost
- Half hardy: light frost only
Everything it needs
9 essentials at a glance
Watering
Sweetpeas prefer consistently moist soil but do not tolerate waterlogged conditions.
Water them deeply once a week, allowing the top inch of soil to dry out between waterings. During hot summer months, you may need to increase watering frequency. Signs of over-watering include yellowing leaves and root rot, while under-watering can cause wilting and stunted growth.
Light
Sweetpeas thrive in full sun, requiring at least 6-8 hours of direct sunlight daily.
They benefit from being planted in a location that receives morning sun and afternoon shade, especially in hotter climates. They can tolerate partial shade but may produce fewer flowers.
Soil
The ideal soil for sweetpeas is well-draining, rich in organic matter, with a pH range of 6.0 to 7.0.
A mix of garden soil, compost, and peat moss or a commercial potting mix designed for flowering plants is recommended. Ensure good drainage to prevent root rot.
Humidity
Sweetpeas prefer moderate humidity levels, ideally around 40-60%.
If the air is too dry, consider misting the plants or placing a humidity tray nearby. Signs of low humidity stress include browning leaf tips and wilting flowers.
Temperature
Sweetpeas thrive in cooler temperatures, ideally between 55-70°F (13-21°C).
They are hardy in USDA zones 3-11, tolerating light frost but not extreme heat. Protect them from temperatures above 80°F (27°C) to maintain flowering.
Fertilizing
Use a balanced fertilizer with an NPK ratio of 10-10-10 or 5-10-10.
Fertilize every 4-6 weeks during the growing season, starting when seedlings are established. Signs of nutrient deficiency include yellowing leaves and poor flowering.
Pruning
Prune sweetpeas to encourage bushier growth and more blooms.
Pinch back the tips of young plants when they reach about 6 inches tall. Remove spent flowers regularly to promote continuous blooming throughout the season.
Repotting
Repot sweetpeas when they outgrow their current container, typically every 1-2 years.
Choose a pot that is 1-2 inches larger in diameter. Signs that repotting is needed include root-bound plants with roots growing out of the drainage holes. Carefully remove the plant, loosen the roots, and place it in fresh potting mix.
Propagation
Sweetpeas can be propagated from seeds.
Soak seeds in water for 24 hours before planting to enhance germination. Sow seeds 1 inch deep in well-draining soil in early spring or fall. Thin seedlings to 6-12 inches apart once they have a few sets of true leaves.
When it's unhappy
Yellow leaves
Why it happens
Often caused by over-watering or nutrient deficiency.
How to fix it
Check soil moisture and adjust watering schedule. Fertilize with a balanced fertilizer if nutrient deficiency is suspected.
Wilting flowers
Why it happens
Can result from under-watering or high temperatures.
How to fix it
Ensure consistent watering and provide shade during peak heat to prevent wilting.
Powdery mildew
Why it happens
Occurs in humid conditions with poor air circulation.
How to fix it
Improve air circulation around plants and apply fungicide if necessary.
Root rot
Why it happens
Caused by overly wet soil and poor drainage.
How to fix it
Ensure pots have drainage holes, and allow the soil to dry out between waterings.
Pests (aphids, spider mites)
Why it happens
Common pests attracted to sweetpeas, especially in warm conditions.
How to fix it
Inspect regularly and treat with insecticidal soap or neem oil if infestations occur.
Care through the year
Spring
In spring, prepare the soil by adding compost and ensure good drainage. Sow seeds directly into the garden or start indoors for earlier blooms.
Summer
During summer, provide consistent moisture and ensure plants have enough shade during the hottest parts of the day. Regularly deadhead to promote blooming.
Fall
In fall, continue to care for sweetpeas until the first frost. If planting for next year, consider sowing seeds in late fall for early spring blooms.
Winter
In winter, protect sweetpeas from extreme cold. If grown as annuals, remove dead plants and prepare the soil for spring planting.
Toxicity & Safety
Sweetpeas are considered non-toxic to pets and children. However, ingestion of large quantities may cause mild gastrointestinal upset. The seeds are not edible and should be kept out of reach.
Good to know
Why are my sweetpea leaves turning yellow?
Yellow leaves on sweetpeas can indicate over-watering or a nutrient deficiency. Check the soil moisture and adjust your watering schedule accordingly.
How often should I water my sweetpeas?
Water sweetpeas deeply once a week, allowing the top inch of soil to dry out between waterings. Increase frequency during hot weather.
What is the best fertilizer for sweetpeas?
A balanced fertilizer with an NPK ratio of 10-10-10 or 5-10-10 is ideal. Fertilize every 4-6 weeks during the growing season.
How can I encourage more blooms on my sweetpeas?
To encourage more blooms, regularly deadhead spent flowers and pinch back the tips of young plants to promote bushier growth.
When should I plant sweetpeas?
Sweetpeas can be planted in early spring or fall, depending on your climate. They prefer cooler temperatures for optimal growth.
Do sweetpeas need support to grow?
Yes, sweetpeas are climbing plants and benefit from trellises or supports to help them grow upwards and produce more flowers.
Are sweetpeas toxic to pets?
Sweetpeas are considered non-toxic to pets and children, although ingestion of large quantities may cause mild gastrointestinal upset.
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