As the vibrant colours of summer fade and the garden prepares for its winter slumber, a thoughtful gardener knows that now is the time to lay the groundwork for next year’s floral abundance. One of the most rewarding tasks for an autumn afternoon is sowing sweet peas. These quintessentially English cottage garden flowers, with their delicate, butterfly-like blooms and intoxicating fragrance, can get a powerful head start if sown before the winter frosts set in.
What are Sweet Peas?
The sweet pea, known botanically as Lathyrus odoratus, is a climbing annual celebrated for its enchanting scent and clusters of colourful, ruffled flowers. The name Lathyrus comes from the Greek word for ‘pea’ or ‘pulse’, while odoratus is Latin for ‘fragrant’, a perfect description for this beloved bloom.
The flower’s history is just as captivating as its perfume. Native to Sicily and southern Italy, the sweet pea was first discovered in the late 17th century by a Franciscan monk, Brother Franciscus Cupani. He was so taken by its intense fragrance that he sent seeds to Dr Robert Uvedale, a schoolmaster and keen horticulturist in Enfield, England. From these humble beginnings, the sweet pea captured the hearts of British gardeners.
It was the Victorian era, however, that marked the sweet pea’s golden age. Scottish nurseryman Henry Eckford dedicated his life to breeding them, transforming the original, small purple flower into the larger, more varied blooms we recognise today. His work earned him the title “King of Sweet Peas” and introduced a stunning array of colours, from soft pastels to deep, velvety maroons.
Why Sow Sweet Peas in Autumn?
While you can certainly sow sweet peas in the spring, an autumn sowing offers several distinct advantages.
The Benefits of Autumn Sowing
- Stronger, Healthier Plants: Sowing in autumn allows the seeds to germinate and develop a robust root system throughout the winter. This head start results in sturdier, more vigorous plants that are better equipped to handle the transition to their final growing positions in spring.
- Earlier Flowering: Autumn-sown plants will almost always flower earlier than their spring-sown counterparts. You can expect your first fragrant blooms to appear as early as May, extending the flowering season by several weeks.
- More Prolific Blooms: The well-established root system enables the plants to produce a greater abundance of flowers over a longer period. More roots mean more energy for producing those beautiful, scented blossoms.
Potential Drawbacks
Of course, there are a few considerations to keep in mind. Autumn-sown seedlings require protection from the harshest winter weather. They will need a cold frame, an unheated greenhouse, or a sheltered spot to prevent them from succumbing to severe frosts, waterlogged soil or hungry mice who find the seeds a tasty winter snack. Spring sowing avoids these challenges, but the resulting plants often take longer to establish.
For most gardeners, the promise of earlier, more abundant flowers makes the small effort of overwintering seedlings well worth it.
How to Sow Sweet Peas in Autumn
Sowing sweet peas is a simple and deeply satisfying process. Follow these steps to give your seeds the best possible start.
1. Choose Your Seeds
Select high-quality seeds from a reputable supplier. There is a vast range of cultivars to choose from, including the highly-scented heirloom varieties like ‘Cupani’ or the large-flowered Spencer types developed by Eckford.
2. Prepare Your Containers
Sweet peas have long taproots that dislike disturbance. For this reason, deep pots or specialised ‘root trainers’ are the ideal choice. Root trainers are deep, grooved cells that encourage the roots to grow straight down, and they hinge open, allowing you to transplant the seedlings with minimal root disturbance.
Fill your chosen containers with a good-quality, peat-free seed compost. Lightly firm it down and water it well, allowing any excess to drain away before sowing.
3. Sow the Seeds
Place two seeds in each pot or cell, pushing them about 1cm (half an inch) deep into the compost. Sowing two seeds per pot is a good insurance policy in case one fails to germinate. If both grow, you can either pinch out the weaker seedling or carefully separate them when planting out.
Cover the seeds with a little more compost, but do not water them again until you see signs of germination. This helps prevent the seeds from rotting in cold, damp conditions.
4. Overwintering Your Seedlings
Once sown, the seedlings need a bright, cool and protected place to spend the winter. An unheated greenhouse, a cold frame, or even a sheltered, sunny windowsill in a cool room is perfect. The goal is to provide enough light for growth without the warmth that would encourage soft, leggy stems.
Keep an eye out for mice, which are notorious for digging up and eating sweet pea seeds. If they are a problem in your area, cover the pots with a sheet of plastic or mesh until the seedlings have emerged. Once germinated, water the seedlings sparingly throughout the winter, only when the compost feels dry to the touch.
Planting Out Your Sweet Peas
As winter recedes and the first signs of spring appear, your sturdy little sweet pea plants will be ready for their final home in the garden.
When to Plant Out
The best time to plant out your autumn-sown sweet peas is from March to April, once the soil has started to warm up and the risk of hard frost has passed. A week or two before planting, ‘harden them off’ by gradually acclimatising them to outdoor conditions. Place them outside during the day and bring them back under cover at night.
How to Plant Out and Provide Support
Choose a sunny, well-drained spot in your garden. Sweet peas are hungry plants, so enrich the soil beforehand by digging in plenty of well-rotted manure or garden compost.
Space your plants about 20-30cm apart at the base of their support structure. Sweet peas are natural climbers and will need a sturdy frame to scramble up. You can use a wigwam of bamboo canes, a trellis against a wall, or netting stretched between posts.
Gently remove the seedlings from their pots, taking care not to disturb the roots, and plant them at the same depth they were in their containers. Water them in well.
Caring for Your Plants
To encourage bushy growth, pinch out the growing tip of each plant when it has developed three or four pairs of leaves. This prompts the plant to produce side shoots from the base, resulting in more stems and, ultimately, more flowers.
Once they start growing, tie the stems to their supports until they begin to climb on their own. Water them regularly, especially during dry spells, and apply a high-potash liquid feed (like a tomato fertiliser) every couple of weeks once they start flowering.
The most important task is to pick the flowers regularly. The more you pick, the more the plant will produce. If you allow seed pods to develop, the plant will think its job is done and stop flowering.
A Garden Filled with Fragrance
By following these simple steps, you can fill your garden with the unparalleled scent and beauty of sweet peas from late spring right through the summer. The small effort of sowing seeds on a crisp autumn day will be repaid a thousand times over when you are able to gather bunch after bunch of these exquisite, fragrant blooms.
Further Reading: Creating a Cottage Garden, Plant Autumn Bulbs Now for a Beautiful Spring Garden