When Can I Plant Out Sweet Peas? The Best Time for Strong, Healthy Growth
Sweet peas (Lathyrus odoratus) are a favorite among gardeners, known for their beautiful blooms and strong fragrance. But timing is key—plant them too early, and they might suffer from frost; plant them too late, and they won’t establish well.
So, when can you plant out sweet peas?
The best time to plant out sweet peas is in early spring, but you can also sow them in autumn for stronger plants the following year.
In this guide, you’ll learn:
✔️ The best time to plant out sweet peas (UK and other climates)
✔️ How to harden off seedlings for outdoor planting
✔️ Step-by-step planting tips for strong, healthy plants
✔️ How to care for sweet peas after planting
Let’s dive into the perfect time to plant out sweet peas for the best results! 🌿🌸
1. When Can I Plant Out Sweet Peas?
The best time to plant out sweet peas depends on when they were started.
Spring-Sown Sweet Peas (January–March Start) 🌸
✔️ Best time to plant outside: March–May (after the last frost).
✔️ Harden off plants for 7–10 days before transplanting.
✔️ Ideal for garden beds, borders, and containers.
Autumn-Sown Sweet Peas (October–November Start) 🍂
✔️ Best time to plant outside: March–April (stronger plants).
✔️ Can withstand cooler temperatures and flower earlier.
✔️ Ideal for overwintering in a greenhouse or cold frame.
Direct-Sown Sweet Peas (Planted Straight into the Ground) 🌱
✔️ Best time to plant seeds outside: October–November or March–April.
✔️ Autumn-sown seeds flower earlier and stronger.
Tip: Sweet peas are frost-hardy, but young seedlings still need protection from late frosts.
2. How to Harden Off Sweet Pea Seedlings Before Planting Outside
If you started sweet peas indoors, they need hardening off before moving outside.
How to Harden Off Sweet Peas:
✔️ Days 1–3: Place outside in a sheltered, shaded area for 2–3 hours.
✔️ Days 4–6: Gradually increase exposure to sunlight and wind.
✔️ Days 7–10: Leave outside all day, bringing indoors at night if cold.
✔️ After 7–10 days, they’re ready for planting outside!
Tip: Hardening off prevents transplant shock and helps stronger root growth.
3. How to Plant Out Sweet Peas (Step-by-Step Guide)
Once hardened off, follow these steps for successful transplanting.
Step 1: Choose the Right Location
✔️ Full sun – Needs at least 6 hours of sunlight daily.
✔️ Well-drained, rich soil – Add compost or manure before planting.
✔️ Provide support – Use canes, trellises, or netting for climbing.
Step 2: Prepare the Soil
✔️ Loosen the soil to at least 30 cm deep.
✔️ Add organic matter for nutrients.
✔️ Improve drainage by mixing in sand or grit if soil is heavy.
Step 3: Transplant Sweet Pea Seedlings
✔️ Spacing: 20–30 cm (8–12 inches) apart.
✔️ Plant at the same depth as in pots to avoid stem rot.
✔️ Water well after planting to help roots establish.
Step 4: Provide Support for Climbing
✔️ Tie young plants loosely to trellises, canes, or netting.
✔️ Pinch out growing tips when plants reach 10 cm tall for bushier growth.
Tip: Mulching around the base retains moisture and prevents weeds.
4. How to Care for Sweet Peas After Planting
Once sweet peas are planted out, regular care helps them thrive.
Watering 💧
✔️ Keep soil evenly moist—don’t let it dry out completely.
✔️ Water deeply 2–3 times per week, especially in dry weather.
Feeding & Fertilizing 🌿
✔️ Apply a high-potash fertilizer (e.g., tomato feed) every 2 weeks.
✔️ Avoid nitrogen-heavy fertilizers—they promote leaf growth instead of flowers.
Training & Supporting Growth 🏗️
✔️ Tie stems loosely to trellises or canes as they climb.
✔️ Remove side shoots if growing for cut flowers (for longer stems).
Deadheading & Pruning ✂️
✔️ Deadhead regularly to prolong flowering.
✔️ If plants become leggy, trim back lightly to encourage new growth.
Tip: Picking sweet pea flowers regularly encourages more blooms! 🌸
5. Common Problems & Solutions When Planting Out Sweet Peas
| Problem | Cause | Solution |
|---|---|---|
| ❌ Seedlings wilting after transplanting | Not hardened off properly | Gradually expose to outdoor conditions before planting |
| ❌ Yellowing leaves | Overwatering or poor drainage | Water only when soil is dry and improve drainage |
| ❌ Leggy growth | Not enough light | Ensure full sun exposure |
| ❌ Few flowers | Too much nitrogen | Use high-potash fertilizer instead |
| ❌ Pest damage | Slugs, snails, or aphids | Use organic pest control like neem oil or copper tape |
Tip: Plant marigolds or nasturtiums nearby—they attract pollinators and deter pests!
6. Final Thoughts: When to Plant Out Sweet Peas for Best Growth
✔️ Spring-sown sweet peas should be planted outside March–May (after hardening off).
✔️ Autumn-sown sweet peas can be planted out March–April for earlier flowers.
✔️ Direct-sown sweet peas can be planted in October–November or March–April.
✔️ Harden off seedlings before planting out to avoid transplant shock.
✔️ Provide full sun, support, and regular watering for strong, healthy growth.
By following these planting tips, you’ll enjoy beautiful, fragrant sweet peas all summer long! 🌿🌸
Are you planting sweet peas this season? Let us know your experience in the comments!
Now you know the best time to plant out sweet peas! 🌿💜 Let me know if you have any questions! 🚀