While the garden currently looks a little sleepy under the January frost, the real work for a spectacular summer sweet pea display starts right now.
Sweet peas. For many of us, these climbing beauties sum up summertime – providing bunch after bunch of honey-scented blooms for the kitchen table.
We wouldn’t blame you for asking why we’re talking about seeds while the scarves and gloves are still firmly on. The truth is, January is the ‘secret weapon’ month for sowing some of your favourite annuals – sweet peas included. By getting your seeds into some soil now, you are tapping into the plant’s natural desire to build a powerhouse of a root system before the spring sun demands upward growth.
The beauty of the slow start
When you sow sweet peas in the heat of May, the plant rushes. It feels the warmth, sees the light, and puts all its energy into growing tall, thin stems. However, a January seedling is a different beast entirely. In the cool (but protected) environment of a cold frame or an unheated greenhouse, the plant stays short and stocky above the surface.
Meanwhile, beneath the soil, something incredible is happening. The roots are exploring, deepening, and strengthening. This ‘slow and low’ start results in a much tougher plant that can handle the summer heat and, crucially, will start flowering weeks before those sown in the spring. If you want to be the first on your street with a vase full of colour, January is your window of opportunity (Gareth agrees! See below for his helpful ‘how to’ video).
Setting the scene for success
Before you start, it’s worth thinking about the home you’re providing for your seeds. Sweet peas are famous for their long, wandering roots. They hate having their toes stepped on, which is why we always recommend using deep pots or ‘rootrainers.’ If you haven’t seen these at Hildreth’s, they are tall, hinged cells that allow the roots to grow straight down without spiralling. When it comes time to plant them out, you simply open the cell like a book and the plant slides out without a single root being snapped.
But if you don’t want to splash out, even an old toilet roll will do the job!
Regarding the soil, don’t overthink it, but do choose quality. A good seed compost will provide the perfect balance of drainage and nutrients. You’re looking for a texture that stays moist but never becomes a boggy mess- seeds need to breathe just as much as they need to drink!
The how to
Sowing the seeds is a wonderfully therapeutic task for a cold afternoon. You don’t need to soak your seeds overnight – most modern varieties have excellent germination rates – but it can help to plump them up. Some gardeners like to ‘nick’ the brown coat of the seed with a bit of sandpaper to help the moisture get in.
Simply tuck your seeds about 3cm deep into the compost. Once they are tucked in, they need a spot that is bright but cool. A windowsill in a spare room is perfect, or a sheltered spot in the greenhouse. The main thing to watch out for during a UK January isn’t actually the cold – it’s the mice! To a hungry field mouse, a freshly planted sweet pea seed is a gourmet meal. Covering your trays with a bit of fine wire mesh or a clear lid until the green shoots appear is a good idea.
Once your seedlings have grown about four inches high and have developed a few sets of leaves, you’ll need to perform the hardest task for any gardener: the pinch. By nipping off the very top growing tip of the plant, you are sending a signal to the roots to stop going up and start going out. This creates a bushy, multi-stemmed plant. Instead of one single vine climbing your trellis, you’ll have a lush, thick wall of flowers.
So pop by, grab your seeds and a bag of compost, and let’s make sure 2026 is the year your garden smells better than ever before. There’s no better way to beat the January blues than by planting a little bit of summer!
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