PlantSowGrow
How to grow Sweet Pea (Spencer Mixed)
Lathyrus odoratus
Frilly, richly scented climbing flowers for cutting from June to September. The more you pick, the more you get.
At a glance: Sow mid March to late April.
When to sow, plant and harvest
Timed for a typical UK garden (last frost mid-April). The app uses your own town's frost dates.
Growing Sweet Pea (Spencer Mixed): what it needs
- Light
- Full sun · 6+ hours a day
- Watering
- Never let them dry out — they stop flowering
- Soil
- Any well-drained soil
- Spacing
- 20 cm
- Height
- 1.8 m
- In pots
- Only in large containers
- Feeding
- High-potash feed every two weeks once flowering
- Hardiness
- USDA zones 2–10
- Difficulty
- Easy
Step by step
- Mid March – late April · 4 weeks before the last spring frost
Sow Seeds Outdoors
Sow thinly where they are to flower, in a sunny spot, into raked, weed-free soil. Sow 1 cm deep in deep root-trainers; soaking seed overnight helps.
- 10–21 days after “Sow Seeds Indoors” · Late March – early April
Check Germination
Seedlings should appear in 10–21 days. Keep the soil moist. If sown outdoors, thin them to 20 cm apart once they have two true leaves.
- 14–21 days after “Plant Out” · Early April – mid April
Pinch Out Tips (optional)
Pinch out the growing tip above the third or fourth pair of leaves for bushier plants with more flowers.
- 14 days after “Pinch Out Tips” · Late April
Add Support
Push in canes or twiggy sticks and tie in stems before they flop.
- 99–129 days after “Check Germination” · Early July – early August
First Flowers — Deadhead Regularly
Snip off faded flowers every few days to keep new ones coming for months. Take a photo for your journal!
- Mid October – early November · around the first autumn frost
Clear or Collect Seed
When frost blackens the plants, pull them up for the compost heap. Leave a few seedheads first if you want to save seed.
_(Leguminosae)_Flower.JPG){kind=link}