Growing Sweet Peas from Seed: A Complete Guide for Beautiful Blooms

Sweet peas (Lathyrus odoratus) are one of the most beloved flowers in the garden, admired for their delicate beauty, climbing habit, and intense fragrance. Growing sweet peas from seed is easy and rewarding, whether you want an early spring display or a summer garden full of blooms.

So, how do you grow sweet peas from seed successfully?

✔️ For early blooms, sow seeds in autumn (October–November).
✔️ For spring planting, start seeds indoors (January–March) or sow directly outside (March–April).

In this guide, you’ll learn:

✔️ The best time to sow sweet pea seeds
✔️ How to prepare and plant seeds indoors or outdoors
✔️ Step-by-step care tips for healthy growth
✔️ How to transplant seedlings and train them to climb

Let’s dive into the complete process of growing sweet peas from seed! 🌿🌸

1. When to Sow Sweet Pea Seeds?

The best time to sow sweet pea seeds depends on how early you want them to flower.

1. Autumn Sowing (October–November) 🍂

✔️ Produces stronger, earlier flowers in late spring.
✔️ Sow seeds in deep pots indoors or in a cold frame/unheated greenhouse.
✔️ Overwinter seedlings and plant them out in March–April.

2. Indoor Spring Sowing (January–March) 🌱

✔️ Best for an early start before planting outdoors in spring.
✔️ Sow in root trainers or deep pots for strong root development.
✔️ Transplant outdoors from March–May after hardening off.

3. Direct Outdoor Sowing (March–April) 🌸

✔️ Sow seeds directly in the ground when frost risk is low.
✔️ Best for warmer climates where winter is mild.
✔️ Flowers appear slightly later than autumn- or indoor-sown plants.

Tip: If you want continuous blooms, plant both autumn and spring-sown sweet peas for a longer flowering period.

2. How to Grow Sweet Peas from Seed (Step-by-Step Guide)

Step 1: Prepare Your Seeds for Germination

Sweet pea seeds have a hard outer coat, which can delay germination.

✔️ Soak seeds in warm water overnight (12–24 hours) to soften the shell.
✔️ If seeds don’t swell, gently nick the outer coat with sandpaper or a nail file.

Tip: Some gardeners skip soaking, but it can speed up germination by several days.

Step 2: Choosing the Right Pots & Soil

✔️ Use deep pots or root trainers—sweet peas develop long roots.
✔️ Fill with well-draining, rich seed compost.
✔️ Avoid overcrowding—sow one seed per pot for the strongest plants.

Tip: Toilet roll tubes make great eco-friendly containers for sweet pea seedlings!

Step 3: Sowing Sweet Pea Seeds

🌿 Best Time: Autumn (October–November) or Spring (January–March).

1️⃣ Make a 2–3 cm (1 inch) deep hole in the compost.
2️⃣ Place one seed per hole, cover lightly with soil.
3️⃣ Water gently to moisten the soil—avoid overwatering.
4️⃣ Place in a cool, bright spot (15–18°C) for germination.

Germination Time: 🌱 7–14 days (depending on temperature).

Tip: Once seedlings emerge, move them to a brighter, cooler place (10–12°C) to prevent leggy growth.

Step 4: Caring for Sweet Pea Seedlings

✔️ Water lightly—keep soil moist but not soggy.
✔️ Move seedlings to a cool but bright location.
✔️ Pinch out growing tips when plants reach 10 cm tall for bushier growth.
✔️ If seedlings look weak, provide gentle support using sticks or small canes.

Tip: Sweet peas grow best in cool temperatures—avoid keeping them in overheated rooms.

3. How to Transplant Sweet Peas Outdoors

Once seedlings are 6–8 weeks old and frost risk is low, they can be planted outside.

🌱 Best Time: March–May (after hardening off).

Step 1: Harden Off Seedlings

✔️ Place seedlings outside for a few hours daily, increasing time gradually.
✔️ After 7–10 days, they’ll be ready for full outdoor conditions.

Step 2: Choose the Right Spot

✔️ Full sun – At least 6 hours of sunlight per day.
✔️ Well-draining, fertile soil – Mix in compost or manure before planting.
✔️ Provide climbing support – Use trellises, canes, or netting.

Step 3: Transplanting Seedlings

✔️ Space plants 20–30 cm apart for healthy growth.
✔️ Water well after planting to help roots establish.
✔️ Tie young plants loosely to supports with twine.

Tip: Mulch around plants to retain moisture and suppress weeds.

4. Caring for Sweet Peas After Planting

Once transplanted, regular care ensures a long flowering season.

Watering 💧

✔️ Keep soil evenly moist, especially in dry weather.
✔️ Water deeply 2–3 times per week.

Feeding & Fertilizing 🌿

✔️ Feed with a high-potash fertilizer (e.g., tomato feed) every 2 weeks.
✔️ Avoid nitrogen-rich fertilizers, which encourage leaves over flowers.

Training & Supporting Growth 🏗️

✔️ Tie stems gently to supports as they grow.
✔️ Pinch out side shoots to promote more flowers.

Deadheading & Pruning ✂️

✔️ Remove dead flowers regularly to extend blooming.
✔️ Trim back leggy growth for bushier plants.

Tip: Cutting sweet peas often encourages more blooms! 🌸

5. Common Problems & Solutions When Growing Sweet Peas from Seed

Tip: If your sweet peas aren’t flowering, cut back excess leaves and switch to a high-potash feed.

6. Final Thoughts: Growing Sweet Peas from Seed Successfully

✔️ For early blooms, sow seeds in autumn (October–November).
✔️ For spring planting, start seeds indoors (January–March) or direct sow (March–April).
✔️ Use deep pots or root trainers for strong root development.
✔️ Pinch out seedlings at 10 cm for bushier growth.
✔️ Harden off seedlings before planting outdoors in March–May.
✔️ Provide climbing support, regular watering, and deadhead often for longer blooms.

By following these simple steps, you’ll enjoy fragrant, colorful sweet peas throughout the season! 🌿🌸

Are you growing sweet peas this year? Share your experience in the comments!

Now you know how to grow sweet peas from seed for a stunning garden display! 🌿💜 Let me know if you have any questions! 🚀