Ornamental · Fabaceae
Sweet Pea
Lathyrus odoratus
Sow it early, cut it often, and let the sweet pea fill the season with scent and color all spring.
Full sun
Every 2–4 days
39–64°F · 4–18°C
50–75 days
Overview
Sweet pea is the flower that scents a whole room from a single small jar. A fast-climbing annual in the pea family, it sends tendrils up any support you set for it, dressing a fence, an obelisk, or a doorway arch in ruffled bloom. That fragrance is its signature, and it is why the flower has held a place in cutting gardens and on windowsills for well over a century.
This is a cool-season plant that shapes the rhythm of the early garden. It comes into its own in the chilly weeks of early spring, carries the border and the vase from May into July, then steps back as heat arrives. The short season is part of its charm, a spring set piece to plan around, and the reward for sowing early is a longer run of that color and perfume.
Sweet peas suit a gardener who enjoys a small daily ritual. Nick and soak the hard seeds, keep the soil evenly moist, and make the evening cut a habit, since picking is what keeps the flowers coming. Let the blooms stand and the plant sets seed and stops, so the pleasing truth is that the more you cut, the longer it blooms and the fuller the vase stays.
Care
The short version: a sunny spot, rich and evenly moist soil on the alkaline side, cool weather, and a standing habit of cutting to keep the flowers and the fragrance coming indoors.
Light
Sweet peas give their fullest display in full sun, though they accept a little afternoon shade where spring warms early. Set them where the light falls freely through the cool months and the flowering, and the fragrance that comes with it, will be the more generous for it.
Water
Keep the soil evenly and consistently moist, watering roughly every 2 to 4 days, and never let the plants dry out while they flower. Water at the base rather than over the top, and choose a spot that drains well so the roots never sit wet.
Soil
Plant them in rich, humus-heavy soil that holds moisture yet still drains, worked through with plenty of organic matter. They lean toward the alkaline, so aim for a pH of 7.0 to 7.5.
Temperature
These are plants of cool weather, at their best between 39°F and 64°F (4°C to 18°C). Growth and flowering both ease off once the season turns hot, which is why an early start makes for the longer show.
Humidity
Ordinary outdoor humidity suits them, so there is no number to manage. Airflow is what matters in the planting, since crowded, muggy corners invite mildew and other leaf troubles that dull the display.
Feeding
Offer a balanced fertilizer about once a month through the growing season. That steady feeding keeps the plants full and the flowers arriving for the vase.
Pruning
Deadhead the spent flowers and keep cutting for the house, which is exactly what keeps the plant producing, since it stops once it sets seed. When the summer heat finally wears it down, lift the whole plant and make room.
Size & spacing
Climbing types reach 3 to 8 feet (91 to 244 cm) and want a trellis, an obelisk, or netting to scale, which makes them a natural for a vertical accent. Give each plant about 2 to 3 feet (61 to 91 cm) of room so air moves through the planting.
When to plant
Sweet peas set their own calendar around cool weather and bow out in heat, so the season is a spring one to plan around. Start seeds indoors 6 to 8 weeks before your last frost, or sow straight outdoors as soon as the soil can be worked, and the vase stays full from late spring until summer heat closes the show. In mild-winter regions, a fall sowing carries the flowers through winter and spring.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: About 6 to 8 weeks before the last spring frost date; in warm-winter areas seed may be sown in fall or late fall for winter and spring bloom
- Plant: As soon as the soil can be worked in early spring; these are cool-season plants
- Harvest: May to July (spring through early summer; declines in summer heat)
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most sweet pea concerns come down to the season winding down or a few familiar pests, and neither should spoil the display. Learn to read ordinary summer decline against a genuine problem, then match what you see below and act while it still makes a difference.
The display fades and plants collapse as summer settles in
A fading, yellowing plant in early summer is simply the season closing, not a disease, because sweet peas are cool-season annuals. Once the heat and humidity settle in, the flowering is finished for the year. Clear the spent plants to keep the border tidy, and in warm regions sow again in fall for a winter and spring return.
Fix:
- Treat as a cool-season annual and enjoy spring bloom
- Remove plants from the garden once they decline
- Sow earlier or, in warm regions, sow in fall for winter/spring bloom
Torn young shoots with telltale shiny trails nearby
Slugs and snails make for the tender seedlings, leaving ragged leaves and glistening trails, and they are busiest in damp spells. An evening walk with a torch, picking them off by hand, does most of the work. Clear away leaf litter and other hiding places, and set a barrier or trap around the young plants to guard the display.
Fix:
- Handpick slugs and snails in the evening
- Reduce moist hiding spots and use barriers or traps around young plants
Curling new growth, clustered insects, and a powdery bloom on leaves
Two problems tend to arrive together. Aphids and mites gather on the soft new growth and twist it, while powdery mildew, leaf spot, or rust settle over leaves left crowded and damp. A firm spray of water clears the aphids, opening the planting restores the airflow, and keeping water off the foliage keeps the leaves clean for cutting.
Fix:
- Wash off aphids with water or treat as needed
- Improve air circulation and avoid overhead watering to reduce foliar disease
Toxicity
For all the charm it brings to a room, sweet pea is a flower to arrange, not to serve. The seeds and pods hold a neurotoxic amino acid that causes lathyrism, with weakness and lasting nerve and bone damage, in people, horses, and livestock who eat enough, along with an upset stomach in cats and dogs. Keep the pods well clear of children, pets, and grazing animals, and enjoy the flowers only in the vase.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Mild
A nibble of leaf or stem can leave a cat drooling, being sick, and off its food. The real concern is the seeds and pods, where a larger or repeated helping can bring weakness and shaky, unsteady movement.
Dogs Mild
Chewing the foliage tends to mean vomiting and an upset stomach. Dogs that crack open and swallow the pods or seeds are the ones at risk of weakness and the nervous-system signs of lathyrism.
Horses Toxic
Horses are badly affected. Eating the plant brings weakness, lethargy, restless pacing, head pressing, tremors, and seizures, and a severe case can be fatal.
Rabbits Toxic
The same neurotoxic amino acids in the seeds and pods make the plant unsafe for rabbits, so keep it well out of reach rather than offering any as forage.
Livestock Toxic
Cattle, sheep, and goats that graze the seeds over time develop lathyrism, with muscle weakness and lasting damage to the skeleton and nerves. Fence them away from the plants entirely.
Birds Toxic
The poisonous seeds and pods make sweet pea a poor choice around poultry and pet birds, which readily peck at seed. Keep the seed pods out of their reach.
People Caution
Despite the name, no part of this plant is food. The pods and seeds are poisonous, and eating seeds over time can cause lathyrism, with weakness and nerve and bone damage, so keep children away from the seed pods.
Keep seeds and pods away from pets and children; do not confuse the ornamental sweet pea with edible garden peas. The pods are inedible and poisonous.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Sweet peas arrive in a few groups, each with its own place in the garden and on the table, some bred for size and long stems, others for pure scent. These are the ones worth choosing by name.
Spencer types
The classic exhibition and cut-flower group, prized for large, frilled, ruffled blooms on long stems that arrange beautifully.
Old-fashioned / Grandiflora types
Smaller in the flower but richest in perfume, carrying the strong, sweet scent that gave the species its name.
Cupani / Matucana
An heirloom bicolor close to the wild original, offering deep maroon and violet flowers with an intense fragrance.
Dwarf / bush types
Compact, mounding plants that need little or no support, which makes them a natural for containers and edging.
How to propagate
Sweet peas grow from seed, and the only thing standing between you and the first jar of flowers is a tough seed coat that needs a little help before it will sprout.
SeedModerate
Sow indoors 6 to 8 weeks before last frost, or direct sow in early spring as soon as soil can be worked; in mild climates sow in fall. · Germinates in roughly 1 to 3 weeks; flowering begins about 50 to 75 days after sowing.
Sweet peas grow from seed, and the hard seed coat is the one thing to see to first. Nick or file each seed and soak it in warm water for about 24 hours before sowing to move things along. Start them indoors 6 to 8 weeks before your last frost, or sow straight into the ground in early spring once the soil can be worked, and in mild-winter regions sow in fall. The seeds come up in roughly 1 to 3 weeks, and the first flowers open about 50 to 75 days after sowing, ready to bring indoors.
Myths
Sweet pea seeds and pods can be eaten like garden peas.
The ornamental sweet pea is not the edible garden pea, however alike the pods appear. Its seeds and pods are poisonous, and eating the seeds over time can cause lathyrism, a serious nerve and skeletal disorder. This is a flower for the vase and the border, never for the plate.
Sweet peas keep flowering all summer long.
They are cool-season annuals whose display runs from spring into early summer. Once the heat and humidity arrive they fade fast and usually need clearing, so plan the sweet pea as a spring feature rather than a summer-long one.