Monty Don says now is the moment to plant sweet peas outside – and shares how to set them up for a summer of tumbling, fragrant blooms
Want a garden filled with sweet peas? Then now is the time to get to work in earnest...
There’s something about sweet peas that feels like the true start of the gardening year. And according to gardening expert Monty Don, April is the best time to get them in the ground.
If you’ve been nurturing sweet pea seedlings indoors or picking up young plants from the garden centre, April is when things start to shift. The soil is warming, the light is returning, and suddenly it feels possible to imagine a garden filled with colour and fragrance once again. And sweet peas, with their climbing habit and irresistible cottage garden charm, are one of the easiest ways to bring that vision to life.
Still, timing is everything. Plant them out too early, and a late frost can undo all your hard work; leave it too late, and you risk weaker growth and fewer blooms. That’s why Monty Don’s advice is so invaluable; if there's one person we trust to get this right, it's him.
Article continues belowWhether you’re a seasoned gardener or trying sweet peas for the first time, getting the basics right now will reward you with months of flowers. From soil preparation to planting techniques, here’s how to give your sweet peas the very best start.
Monty Don's advice for planting sweet peas
Whether you’re a seasoned gardener or trying sweet peas for the first time, getting the basics right now will reward you with months of flowers. And you'd best believe that if Monty Don says it's time to plant sweet peas outside in April, we'll be running to do exactly that.
Thankfully, this advice is a little more expansive than just the month. From soil preparation to planting techniques, here’s how Monty recommends you give your sweet peas the very best start.
1. Time it right
'The time to plant out sweet peas into the garden is mid-April in the south and towards the end of the month further north,' writes Monty Don via his blog.
This staggered timing reflects the UK’s habit of muddling its climate. In milder southern regions, the soil warms earlier, making mid-April ideal. Further north, it’s worth waiting a little longer to avoid those awkward cold snaps that could check growth or damage young plants.
If in doubt, keep an eye on overnight temperatures; sweet peas are hardy, but they don’t enjoy sitting in cold, waterlogged soil. A short delay is always, always, always far better than planting into unfavourable conditions.
2. Prepare the soil for stronger plants
It’s time to plant sweet peas outside in April, says Monty Don, but only if you've prepped your soil properly.
'Sweet peas grow best in rich soil with plenty of moisture and in cool – but not cold – conditions, so the more you can enrich the soil with lots of compost (I'm a big fan of Miracle-Gro's premium compost, £11.99 at Amazon) or manure before planting, the better they will grow,' he says.
This step is crucial. Sweet peas are hungry plants, and giving them nutrient-rich soil from the outset sets them up for strong growth and abundant flowering. Before planting, then, dig in plenty of well-rotted compost or manure, working it into the top layer of soil. This not only feeds the plants but also improves soil structure, helping it retain moisture without becoming waterlogged.
If your soil is on the lighter side, adding organic matter will help it hold onto water—something sweet peas rely on as they grow quickly through the spring. I also recommend adding an organic fertiliser like envii SeaFeed extra, £13.95 for 1L at Amazon.
3. Give them the right support
Sweet peas are natural climbers, so providing support early on is key.
'I like to grow mine up bean sticks arranged as a wigwam, but any support will do from bamboo canes to chicken wire,' says Monty Don.
A wigwam of canes is both practical and visually appealing, creating a focal point in the garden while giving plants plenty of space to climb. However, you don’t need anything elaborate; trellises like this decorative trellis panel (£19.80 from Amazon), netting, a simple row of canes or even a neat obelisk, like this £12.99 budget-buy from Amazon will work just as well.
Attach a trellis to a wall or fence to train it upwards.
If it's good enough for Monty, it's good enough for us.
Add drama to your sweet peas with a tall obelisk.
4. Avoid overcrowding
One of Monty Don’s most useful tips for planting out sweet peas in April is about thinning out seedlings.
'One word of caution. The aim is to grow strong, healthy individual plants, so if you buy a pot with lots of seedlings, I think it's better to divide each pot into two or three,' he says. 'Then plant these sections at the base of each support so they have less competition, and you should end up with more flowers.'
It can feel counterintuitive to separate seedlings, but overcrowding leads to competition for nutrients, water, and light. By dividing them into smaller groups in individual seedling pots (you can pick up a 50-piece set at Amazon for £9.99), you’re giving each plant the space it needs to thrive... and giving yourself more blooms later down the line, too.
FAQs
Can you plant sweet peas outside in April?
You can absolutely plant sweet peas outside in April. The trick, according to Monty Don, is to 'plant two or three plants to each stick or support and water them in very well before mulching them thickly to keep them weed-free and to stop them drying out'.
Mulching is another essential step, according to Christopher O'Donoghue, director of Gardens Revived. 'I always recommend a thick layer of organic mulch at the best of times, but definitely with sweet peas in April,' he says. 'It's the best way to help retain moisture, suppress weeds, and keep the soil cool.'
All of the above? Especially important as temperatures begin to rise later in spring.
Is it too early to plant out sweet peas in the UK?
Depending on where you are in the UK, sweet peas can be sown directly into the ground in April or May.
'For me, it’s less about the calendar and more about what’s happening outside my window,' says Christopher O'Donoghue, director of Gardens Revived. 'If the soil has started to warm up and the worst of the frosts has passed, I’m happy to plant them out. If it still feels chilly or there’s a cold snap on the way, I’ll hold off and keep them sheltered a bit longer.'
He adds that, if you want to plant sweet peas outside, it’s better to wait a week or two than risk going too early. Once they’re in and settled, they’ll quickly catch up and reward you with stronger, healthier plants.
Planting sweet peas in April à la Monty Don is one of those simple gardening jobs that pays off in the most joyful way: delicate flowers, an abundance of colour, and fantastically fragranced blooms.
Time to set to work, then...
