Growing Sweet Peas

Sweet Peas are renowned for their delicate beauty, with a spectrum of rainbow colours ranging from soft pastels to vibrant hues. Their amazing fragrance fills the air with a sweet, intoxicating aroma, and their dainty petals and graceful tendrils add a touch of elegance with irresistible scent.-

Selecting Sweet Pea Varieties

The spencer varieties are very popular due to the fact that there are sooooo many varieties to choose from and also the long stems and large flowers make them ideal for exhibition and cut flower production. They require around 12 hours of daylight to bloom and do not need high temperatures so are idea for outdoor growing in the UK.

Spring Sunshine sweet peas only require 9-10 hours of daylight so will bloom earlier than the spencer varieties but they are more suited to greenhouse production as they do like the heat. For growers in the south of England its definitely worth experimenting outdoors and in a warm year you will still get success with these if grown outdoors.

When to Sow Sweet Peas (Autumn vs Spring)

One of the biggest questions I’m asked is “When should I sow my sweet peas? ”And the truth is — you have two perfect windows: Autumn and Spring. Each one gives you slightly different benefits, so here’s how to choose the right timing for your garden.

🍂 Autumn Sowing (Sep – Nov)

Autumn sowing is my favourite for strong, early-flowering plants — and it’s what many UK flower farmers do.

Autumn sow if you want:

• earlier blooms the following spring

• sturdier, more cold-tolerant plants

• longer stems for cutting

• a head start while the garden sleeps

Sweet peas are hardy annuals, so the cool weather doesn’t bother them. Just keep autumn seedlings somewhere bright, cool and frost-free — a cold frame, unheated greenhouse, or polytunnel is perfect.

🌸 Spring Sowing (Feb – May)

If you missed the autumn window (or your garden is in a very cold, exposed spot), spring sowing works beautifully too.

Spring sow if you want:

• slower, steadier seedlings

• an easier start if you’re new to growing

• to avoid managing winter seedlings

• to sow indoors with plenty of light

Spring-sown sweet peas catch up surprisingly quickly — especially once the weather warms and daylight increases.

When Not to Sow Sweet Peas

Avoid sowing in December or January unless you have excellent light levels. Winter seedlings often become:

• tall

• leggy

• stretched

• weak

…simply because the daylight isn’t strong enough. Strong light = strong plants.

So, Which Should You Choose?

If you want…	Sow in…
Early flowers	Autumn (Sep–Oct)
Strong stems for cutting	Autumn
Easiest beginner-friendly timing	Spring (Feb–Mar)
Low-maintenance seedlings	Spring
A head start on the season	Autumn

Both methods work — you’re not “late” and you’re certainly not behind. You’re just choosing the window that fits your growing style and your local climate.

Succession Sow for the Best Results

If you want a long sweet pea season, sow a few in autumn and a few more in spring. You’ll extend flowering and hedge your bets against any unexpected weather swings.

​Planting Seeds

Sweet Peas can be sowed direct into the garden where they are to flower, during springtime,  however I prefer to sow into deep pots as it gives ultimate control.

If you chose to sow direct, sow seeds 1-2cm deep into the ground in early spring, once the soil has warmed up and the risk of frost has passed. Sow along or around a supporting structure like a trellis or fence. 

If sowing in pots ensure to chose something with a deep root run. Root trainers are popular with home gardeners and I have used them in the past, however I have found that large 15-20cm pots do just as god a job and I can sow around 10 seeds to a large pot very quickly without the faff of root trainers, then tease them apart at plating time,

For Autumn sowed seeds overwinter in a greenhouse or cold frame just to give a little protection from ice and snow, and to stop them from getting waterlogged and rotting. The only thing to watch out for if specifically growing indoors is damping off. Water from below only when the soil is dry and ensure good airflow and place the outside on warm(ish) days to prevent the spores from spreading over winter. Increasing watering only when the weather warms and the surface of the soil can dry out to prevent damping off.

These seedlings will be frost tolerant and can be planted out earlier than spring sowed seeds. I plant mine out in around March time as by then they are usually so big they are literally screaming at me to get them out.  I've even covered the with plastic bottles before to give the a little protection as they act like a mini greenhouse.

Pinching

Once seedlings have developed their first two sets of leaves they can be pinched, this will send a signal to the plant to grow more stems and create a bushier plant  with more flowers.  For my over wintered Sweet Peas I usually do this in January as by then they are usually getting very tall and I struggle to fit them into may cold frame. Although you will find that autumn sowed Sweet Peas may naturally branch due to the tips naturally getting "Nipped" by the frosts.  

Cuttings

Sweet Peas can also be grown from cuttings. By keeping the pinchings and propagating them new plants can be made for free. Check out step by step instructions on our page Sweet Peas from Cuttings.

Watering

Keep the soil consistently moist but not waterlogged, especially during dry spells. Water at the base of the plants to avoid wetting the foliage, which can lead to fungal diseases.

Location

Sweet Peas thrive in well-drained soil and prefer full sun, although they can also be grown in part shady locations too. I grew them last year very successfully in an area which receives sunshine in the morning up to around mid day, and is then in shade for the rest of the day. They do take a little longer to start flowering but will go through to September. Select a spot in your garden that receives around 6 hours of sunlight per day and they should still do well.

Feeding

Before planting, enrich the soil with organic matter such as compost to improve it's fertility and drainage. Sweet Peas are hungry feeders so it's a good idea to feed them every couple of weeks until they set seed with something like liquid seaweed. Then once the buds start to form feed with a high potassium fertilizer such as Tomorite. Sweet Peas prefer slightly alkaline soil with a pH level around 7.0.

Providing Support

As Sweet Peas grow, they will need support to climb. Install a trellis, bamboo stakes, or a wire fence for the vines to cling to as they grow. This helps prevent the plants from becoming tangled and promotes better air circulation, reducing the risk of disease.

Pruning

Pinch off the growing tips of the vines when they reach about 6 inches in height to encourage branching and more flower production. Deadhead spent blooms regularly to prolong the flowering period. 

Some growers believe that removing tendrils can redirect the plant's energy towards flowering rather than growth. By eliminating tendrils, the plant focuses more on producing flowers instead of investing energy in climbing and expanding its reach.  Removing tendrils can also help prevent  them tangling into flowers and ensure that the plants grow upward in a more organized manner.

It is essential to note that removing tendrils from Sweet Peas is not necessary for their overall health or growth. Tendrils play a natural role in the climbing behaviour of these plants, and they can contribute to the plant's stability and ability to reach sunlight. Additionally, some growers and florists may appreciate the aesthetic appeal of tendrils as part of the plant's natural form.

Pest and Disease Management

Keep an eye out for common pests like aphids and spider mites, which can be rinsed off with a strong stream of water or controlled with insecticidal soap. Prevent fungal diseases by providing good air circulation, avoiding overhead watering, and promptly removing any diseased foliage.

Harvesting

Regular harvesting and deadheading encourages more flowers to bloom and prevents them for setting seed too quickly. Autumn sowed Sweet Peas will last through to midsummer before exhausting themselves, and late spring sowed seeds will bloom to Autumn. 

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