From seedling to success: Our guide to growing sweet peas from seeds

Very few annual flowers have the lasting charm of sweet peas. They fill the garden, house and life with a lovely scent and bright colour. Read our sweet pea growing guide for information on the best sowing and gardening practices for growing sweet peas.

About sweet peas, the stars of the garden

Lathyrus odoratus, aka the sweet pea, is an annual flower available in a huge range of colours. You will find the pretty plant in pearly whites, ice-cream pastels and rich, inky purples and magentas. These dainty winged blossoms can be found at home in a cutting garden, border garden or trailing on a trellis or arch.

Sweet peas grow better inland than in coastal regions, but we’re going to take you through how to trick your sweet peas to grow in even the warmest of areas.

Easy PEAsy growing

The ideal temperature for sweet peas to germinate is about four degrees celsius — that is pretty cold and in South Africa, our coastal cities rarely reach such low temperatures. So how do we solve this growing dilemma?

Lay your sweet pea seeds on a moist paper towel and place them in an airtight container, then refrigerate overnight. We recommend plain, white paper towels because they are free of toxic dyes that could harm your seed.

This method exposes the seeds to high humidity levels, allowing the seed to absorb enough moisture for the embryo to swell, put out roots and break through the seed coat. As the sweet pea seeds absorb the moisture from the damp paper towels, the cool temperatures inside the refrigerator encourage the sweet pea seed to quickly germinate. This speed of germination seldom happens in the garden or even in seed-starting pots.

It’s best to plant the germinated seeds immediately so they do not rot from too much moisture.

Beautiful Pink Sweet Pea flowers

How to check your seeds when growing sweet peas

It’s a good idea to check the viability of your sweet pea seeds. This tells you how many seeds to put in each hole and if the seeds will germinate.

Using the above method of germinating your seeds with a damp paper towel in the refrigerator makes testing the viability of your seeds easy. The magic of germination happens overnight in the fridge and by the next day, you will know how viable the seeds actually are.

Planting growing sweet peas

Once germinated, it’s time to plant your pea seedlings.
Sweet peas are happiest planted with their heads in the sun and their roots deep in cool, moist soil. When possible, plant low-growing annuals in front of them to shade their roots.

It is best to plan on sowing your seedlings in the cooler months of the year. July through to September are the ideal months to grow your sweet pea plants.

Also, choose a well-drained site. Alkaline soil which retains moisture but drains well is best for growing sweet peas. Sprinkle some Wonder Dolomitic Agricultural Lime on the surface of your ground if your soil tends to be acidic.

You’re going to want to dig a nice deep trench of about 10 cm in depth. Make holes with a pencil and drop the seedlings in gently. Press down on the soil to firm it up and shut out any light in the beginning stages of growth.

Grow care

Overnight germination eliminates the 7 — 14 day range that sweet peas typically need to germinate — which in turn leads to an earlier harvest.

As seedlings emerge and grow, gradually fill in the trenches you’ve dug. Raking more soil up to them.

Remember to keep the soil moist. If you put your finger into the soil bed to its first joint and the soil is dry, water them at the soil level and do so in the morning; growing sweet peas can suffer from bud drops.

If you want to add nourishment, use our range of fertilisers, which are high in potassium, as nitrogen feeds encourage too much top growth.

When plants become established, mulch well to keep the soil cool and moist. If you mulch, you may not need to water your sweet peas unless the soil gets dry.

To encourage bushy growth, pinch off the tops when plants are approximately 15 cm tall — not before or you’ll encourage premature side-shoot development.

Offer sweet support to your sweet peas

Except for the bush types, sweet peas are real climbers. Give them about two metres of good support. If you don’t have a fence or trellis, provide brush, chicken wire or bushy, stubbly twigs that they can cling to.

Tie the first few stems into the support to give the plants a good start and the rest will follow. When they grow to anywhere between 10 to 29 cm high, pinch out the middle growing tip with your thumb and forefinger. This will lead to sturdier plants.

Picking Flowers

Pick the colourful flowers for bouquets often and the plant will put energy into more blooms instead of going to seed. The more you pick the more they produce, right until the first sign of frost or cold.

Gather the flowers in the morning when the dew is still on them. This is when their scent is the sweetest.

Blue Pink Red White Sweet pea colours

Fun facts about sweet peas

The sweet pea is an essential member of a late-Victorian garden. Victorians loved sweet peas for their colour, diversity and fragrance.

Sweet peas are one of the April birth flowers.

Pests and diseases to watch for

Slugs and snails may attack young growing sweet peas. Try Efekto’s Snailban to protect your youthful plants.

Fungal diseases such as powdery mildew, rust, and various leaf spots are also very common.

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