Annual
Sweet Pea
Lathyrus odoratus · Fabaceae
Also called: Annual Sweet Pea, Fragrant Sweet Pea
Sweet Pea (Lathyrus odoratus) is a moderate-water annual well suited to Tucson and the low desert. It's a fast-growing annual.
Sweet Pea at a glance
- Water use
- Moderate (established)
- Sun
- Full sun during the cool season; benefits from afternoon shade as spring warms.
- Mature size
- Climbing types 4-6+ ft (on support); bush/dwarf types 1-2 ft
- Growth rate
- Fast
- Bloom
- Pink, lavender, purple, blue, red, white, cream, and bicolors; many are highly fragrant, Late winter into spring (roughly Feb-May) in the low desert
- Cold hardiness
- Frost-tolerant of light frost and prefers cool weather; vines decline rapidly once daytime temperatures consistently exceed ~85-90 F.
- Soil
- Rich, deep, well-drained soil amended with compost; prefers neutral to slightly alkaline pH, which suits Tucson soils when organic matter is added.
- Native range
- Sicily and Southern Italy / Eastern Mediterranean
- Best used as
- Cut flowers (prized for fragrance), Trellises, fences, and arbors, Cottage gardens, Containers (dwarf types)
- Wildlife
- Fragrant flowers attract bees and butterflies.
- Toxicity
- The ornamental sweet pea seeds/pods are toxic if eaten in quantity (contain a lathyrogen, aminopropionitrile); the ASPCA lists sweet pea as toxic to horses, and ingestion can cause GI upset in dogs and cats. This is NOT the edible garden pea (Pisum sativum) -- do not eat. Keep seeds away from children and pets.
How to grow Sweet Pea in Tucson & the low desert
Watering
Water deeply and consistently to keep roots moist; about every 3-5 days, more as the weather warms and during bloom. A cool-season annual in Tucson: sow seed in fall (Oct-Nov) and again in late winter; for best results pre-soak or nick seeds before sowing.
Fertilizer & nutrients
As a legume it fixes some nitrogen; amend soil with compost and add phosphorus at planting. Feed lightly with a balanced or bloom (higher-P) fertilizer every 2-4 weeks once vines establish; avoid excess nitrogen, which favors foliage over flowers.
Pruning & care
Pinch seedlings at 4-6 in to promote branching; pick or deadhead flowers frequently to keep vines blooming, since allowing seed pods to set stops flower production. Provide a trellis or netting for the climbing types.
Notes
Plant for fragrance and cut flowers; sow seed in fall and/or late winter in Tucson and grow on a trellis through the cool season, harvesting before summer heat. Important: ornamental sweet pea is NOT edible despite the name -- the seeds are mildly toxic, unlike culinary garden peas.
Sources: ASPCA Toxic and Non-Toxic Plants (Sweet Pea); University of Arizona Cooperative Extension cool-season annual guidance; Tucson low-desert planting calendars; Missouri Botanical Garden Plant Finder