How to Grow Sweet Peas from Seed

Did you know that sweet peas (Lathyrus odoratus) rank among the top 10 most popular cottage garden flowers in the UK and North America? Loved for their nostalgic scent, ruffled blooms, and endless color options, sweet peas can transform any outdoor space into a fragrant paradise. Yet, many gardeners struggle with getting them started from seed—facing weak sprouts, failed germination, or lackluster blooms.

In this guide, you’ll learn how to grow sweet peas from seed—from selecting the right variety to transplanting and tying in their stems—using expert tips and proven horticultural data. Whether you’re a beginner or seasoned gardener, this post will help you grow robust, blooming vines that last all season.

Why Choose Sweet Peas?

Sweet peas are more than just pretty flowers—they offer several benefits that make them a must-have in any garden:

• Fragrance: Their delightful scent is unmatched by many other garden flowers.
• Long Blooming Season: With proper care, sweet peas can flower from late spring through summer.
• Versatility: They thrive in borders, containers, and as cut flowers.
• Pollinator-Friendly: Bees and butterflies love them!

If you’re looking for a low-maintenance yet high-reward plant, sweet peas are an excellent choice.

Best Amazon Picks for Growing Sweet Peas

• Biodegradable Seed Starter Trays
• Organic Seed Starting Mix
• Electric Seedling Heat Mat
• Heavy-Duty Garden Trowel

Choosing the Right Sweet Peas for Your Garden

Not all sweet peas are the same. There are three main types to consider:

1. Spencer Sweet Peas – Large, ruffled blooms with strong stems, ideal for cutting.
2. Grandiflora Sweet Peas – Highly fragrant with smaller but abundant flowers.
3. Dwarf/Bush Sweet Peas – Compact varieties perfect for containers and small spaces.

Pro Tip: Look for heirloom varieties like ‘Cupani’ or modern hybrids like ‘Matucana’ for exceptional fragrance and color.

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How to Sow Sweet Pea Seeds

Growing sweet peas from seed is simple if you follow these steps:

1. When to Sow Sweet Peas

• Indoor Sowing: Start seeds 6-8 weeks before the last frost (late winter/early spring).
• Outdoor Sowing: Direct sow in early spring (once soil is workable) or in late autumn for early blooms.

2. Pre-Sowing Preparation

Sweet pea seeds have a hard coat, so soaking them overnight in water or nicking them with a file (scarification) improves germination rates.

3. Planting Sweet Peas: Indoor vs. Outdoor Sowing

Indoor Sowing (Recommended for Early Blooms)

• Use deep pots or root trainers (sweet peas dislike root disturbance).
• Fill with well-draining seed compost.
• Plant seeds 1 inch deep, 2-3 per pot.
• Keep at 55-65°F (13-18°C) until germination (7-14 days).

Outdoor Sowing

• Choose a sunny, sheltered spot with fertile, well-drained soil.
• Sow seeds 1 inch deep, spacing them 4-6 inches apart.
• Protect seedlings from slugs and frost with cloches or netting.

How to Transplant Sweet Pea Plants

Once seedlings have 2-3 sets of true leaves, they’re ready for transplanting.

1. Harden Off: Gradually expose indoor-grown seedlings to outdoor conditions over a week.
2. Prepare the Soil: Enrich with compost or well-rotted manure.
3. Planting Depth & Spacing:

• Space plants 6-8 inches apart.
• Plant slightly deeper than in pots to encourage strong roots.

1. Support: Install trellises, obelisks, or netting at planting time to avoid damaging roots later.

Pro Tip: Pinch out the top growth when seedlings are 4-6 inches tall to encourage bushier growth.

How to Tie in Sweet Pea Stems

Sweet peas are natural climbers but need guidance to grow vertically.

• Use soft garden twine or pea rings to gently tie stems to supports.
• Check weekly and train new growth to prevent tangling.
• Avoid tight ties that can damage stems.

How to Care for Sweet Peas

Watering

• Keep soil consistently moist (not waterlogged).
• Water at the base to prevent mildew.

Feeding

• Apply liquid tomato fertilizer every 2-3 weeks once buds form.

Deadheading

• Remove spent flowers daily to prolong blooming.

Pest & Disease Control

• Aphids: Spray with soapy water or introduce ladybugs.
• Powdery Mildew: Ensure good air circulation and avoid overhead watering.

FAQs About Growing Sweet Peas

1. Do sweet peas come back every year?

Most sweet peas are annuals, but perennial varieties like Lathyrus latifolius exist (though they lack fragrance).

2. Why are my sweet peas not flowering?

Possible causes:

• Too much nitrogen (encourages leafy growth over blooms).
• Lack of sunlight (sweet peas need 6+ hours of sun daily).
• Insufficient deadheading.

3. Can I grow sweet peas in pots?

Yes! Choose dwarf varieties and use a deep container (at least 12 inches) with good drainage.

Final Thoughts

Growing sweet peas from seed is a rewarding experience that fills your garden with color and fragrance. By following these steps—choosing the right variety, proper sowing, transplanting carefully, and providing consistent care—you’ll enjoy an abundance of blooms all season.

Ready to start? Grab some sweet pea seeds, follow this guide, and watch your garden transform!

Do you have tips for growing sweet peas? Share them in the comments!