When to plant sweet peas outside to fill your garden with vibrant blooms and heavenly fragrance come summer

Sweet peas are those pretty little blooms that make for a great source of colour and beautiful fragrance in a garden. And as we find ourselves in the midst of spring, you’re probably wondering when to plant sweet peas outside to inject your garden with their vibrancy and scent once they bloom in the summer.

Whether you’re sowing them directly to the ground or transferring them from indoors as many experts recommend, getting the timing of planting them outside right is a crucial part of how to care for sweet peas, go too early and you risk frost damage.

So to avoid any risks, our gardening pros recommend the ideal time to plant your sweet peas outside for successful growing and flowering in your garden.

When to plant sweet peas outside

Sweet peas are one of the fastest growing climbing plants perfect for privacy in the garden or on the patio. But to get to the level of making your sweet peas into a privacy screen, one must know when they can be planted outside.

‘You can usually plant sweet peas outdoors once the risk of frost has passed, which is generally around late May,’ says Petar Ivanov, gardening expert at Fantastic Gardeners.

But if you’re starting your sweet peas indoors, then you can begin the transition by taking them outside for a little bit at a time to get them used to the conditions. 

‘Before planting them, you’ll need to help them harden off by taking them outside during the day when the weather is warm and returning them back indoors during the night when it’s colder,’ Petar explains.

Petar Ivanov

Petar Ivanov is one of the company's top-performing experts and manages over six teams of gardeners, delivering stunning landscape results and fostering a deep connection with nature through his work.

Jamie Shipley, gardening expert and managing director at Hedges Direct, continues ‘Sweet peas are what is known as “hardy annuals'' - plants which carry out their life cycle within one season of the year. Although they can tolerate a light late spring frost it’s best to sow hardy annuals between late March and May, as the soil begins to warm up. I recommend starting your seeds off inside before planting out the seedlings in May.’

What to do before planting sweet peas in the garden

Before it gets to the right time when to sow your sweet peas, there are a few things you should take care of first so that the plant thrives once planted.

‘Before thinking about when to plant sweet peas outside, it’s important to prepare the area for planting,’ says Hannah Rowson, assistant garden centre manager at J.Parker’s. ‘Despite being great growers, sweet peas do still need some encouragement and support. Because they grow quite tall, they need support. Whether that’s in the shape of a trellis or a homemade wigwam.’

Jamie adds, ‘Choose a part of your garden with moist but well draining soil and enough direct sunlight throughout the day - but also remember to choose a place where you’ll be able to appreciate the beautiful fragrance once the sweet peas bloom.’ 

FAQs

What months do sweet peas grow?

‘When your sweet peas bloom will largely depend on when you’ve planted them and what the weather where you live is,’ Petar says. ‘Generally, in the UK that should happen in June and July. Also if you cut them just a tiny bit every now and then water them well and deadhead the old blooms, they can keep flowering throughout all of the summer and even in October.’

But traditionally, June is the sweet pea season in the UK.

Can I grow sweet peas in containers?

Yes, sweet peas can be grown in containers if you don’t have the space in borders. But you need to provide them with the right planter, soil and spot.

‘You can plant and grow sweet peas in pots or containers but you’ll still need to provide them with a good sunny location and peat-free compost that’s combined with a slow-release fertiliser. If they’re planted in containers and you don’t have an outside garden, ideally, find a bright window to place them on,’ Petar says.

Jamie concludes, ‘Make sure to choose a deep enough container to house the large root system of a sweet pea comfortably. You’ll need a pot at least 20 centimetres deep and it’s best to choose a long, narrow pot to help the roots establish a deep system.’

So while it’s not quite the right time yet, you will soon be able to take your sweet peas outside into the garden.