How to grow sweet peas

There is often confusion about when in the spring is the right time to plant out Sweet Peas. Sweet peas are hardy annuals, which means they will tolerate cold, even a light frost, and can survive below freezing. They are tougher than they look and will take a frost down to around -4.  Protect the Sweet Peas with a fleece if a hard frost or prolonged period of low temperatures is forecast.

As Sweet peas are hardy, you can plant them out earlier to get a head start. Sweet Pea can be planted from March onwards. They are best grown with support, such as a trellis or an obelisk, and tie the sweet peas in.  

If you want straight stems and sweet peas which grow up the frame and not a tangled bunch, it is necessary to remove the tendrils and not to let these grow unchecked.  Why?  See how to get straight stems on sweet peas.

Keep picking sweet peas, don't let the seed head form. If you are not sure about seed pods, check out the image the seed pod is ringed in red.

Sweet Peas are quick and easy to germinate, a little heat will speed up germination, but it is not essential. You can germinate Sweet Peas on a warm windowsill, conservatory or using a heated propagator to get a temperature of about 15C/ 59F. Autumn sown Sweet Peas will germinate in a greenhouse/lean to with no additional heat. When growing Sweet Peas from seed, the choice of container is important. Sweet Peas, like many legumes including peas and beans, have long roots, which means it's important to plant them into a deep container, and not a regular pot, to give a long root run.

You can use either root trainers sold by all garden centres, or cheaper and just as easy toilet roll holders, they  are both illustrated in the image. If you are sowing Autumn sweet peas to over winter, they are best in root trainers as there is a risk the cardboard tubes will get damp, disintegrate and /or encourage mould over the winter. Equally, the cardboard tubes are fine for a Spring sowing of sweet peas. Just take care when watering, not to soak the tube.

Put two/three seeds into the container, placing the seed near the top to give plenty of room for the roots to grow down. Sprinkle with a light covering of compost, spray with water so the compost is moist, but not too wet and place in a warm place. It's essential for germination to cover with a lid or clear polythene. Germination should occur within a few days and as soon as the sweet pea seedling is a few centimetres above the soil, remove it from the propagator or take off the cover to prevent the seedling from getting too warm, which will make it sappy and leggy. Only use the heat to speed up germination. 

Sweet peas can be successfully germinated either in the spring or in Autumn in an unheated greenhouse and overwintered. Autumn-sown sweet peas tend to flower earlier in the year, and by sowing both in Autumn and Spring, the flowering season can be extended.