Coriander, onions and basil planted in December can produce impressive harvests in just a few months’ time, according to gardening expert Benedict Vanheems
Michael Moran Audience Writer
04:17, 04 Dec 2025
A greenhouse is a real asset at this time of year – if only as a hideaway!(Image: Westend61 via Getty Images)
Now that December has arrived, many of us will be slowing down a bit as we anticipate a peaceful festive period. However, for gardeners, the work never quite ends, and there are several kitchen garden essentials that need planting this month if you’re hoping for optimal results next year.
After all, as gardening expert Benedict Vanheems highlights: “The days will soon be getting longer and it’s only a few short months before the bulk of sowing begins in earnest.”
In particular, says Vanheems, there’s a long-standing tradition of planting onions on Boxing Day if you’re aiming to showcase some enormous vegetables at your local garden and produce show next year.
There are also several other kitchen staples that will thrive remarkably well if planted in the coming weeks. Benedict reveals on his GrowVeg YouTube channel which seeds you should sow now to achieve the finest results.
Coriander
There’s nothing like adding fresh home-grown herbs to your recipes(Image: Getty)
Coriander, or Cilantro as it’s known across the pond, is a multi-purpose herb that works brilliantly in everything from straightforward soups and sausages to flavourful Mexican cuisine. Just bear in mind that roughly 10% of Europeans perceive the herb as tasting like soap, so check with your guests first!
One of the hurdles when cultivating coriander is that during warmer spells, it can be susceptible to “bolting,” or early flowering: “That’s absolutely fine if you want the seed pods to harvest the seeds to grind into coriander powder,” Benedict says, “but if you’re after the juicy, aromatic leaves, autumn or winter is a great time to grow coriander.”
By encasing your coriander seeds in a small pouch of cotton or muslin fabric, you can pre-germinate them by immersing them in water overnight to activate them, then giving them a quick dip twice daily.
After roughly a week, they should be prepared for planting. Distribute them very gently into a tray of compost, being careful not to harm their fragile roots.
Letting them establish themselves in a cold frame, or even on a sunny window ledge, should provide your coriander plants with a strong foundation.
Within approximately six to eight weeks, the leaves should be ready for harvesting and, if you’re cautious not to harm the growing-point, you might even be fortunate enough to secure a second crop.
Benedict has one additional suggestion for gardeners: “Cilantro, or coriander seed, can be a little bit expensive so it’s worth letting a few plants bolt in the summer so you can harvest your own seed and save yourself a few pennies too.”
Onions
Planting on Boxing Day should guarantee really big onions next year(Image: Getty)
“Now is the perfect time to begin growing onions from seed,” advises Benedict, “particularly if you’re aiming for impressively large, football-sized champion onions.”
The day after Christmas is traditionally when onions are sown for super-sized ones. Start with a well-sifted all-purpose potting mix. If your goal is to grow colossal onions to impress fellow gardeners, choose a variety like Exhibition or Showmaster which, as their names imply, are chosen for their size.
Benedict further suggests not planting your onions outdoors immediately for the best results: “To get these germinated I’m going bring them indoors into the warmth of the house and then they will come back out here once they’re up. Then, as light levels improve within about a month or so, growth should really start to pick up.”
He also recommends that if you’re feeling particularly competitive, consider placing your onions under grow lights for the first month or so to give them a significant head start.
Basil
Just rubbing the leaves of a basil plant will give you a feeling of summer(Image: Getty)
Basil, another essential garden herb crucial in many Italian recipes, is surprisingly easy to cultivate. It’s especially rewarding for those who don’t have a large garden or allotment and need to find plants that will thrive indoors.”
“Basil is a great one to grow on a window sill or under grow lights,” says Benedict, adding that the plant’s vibrant green leaves and aromatic scents are the perfect remedy for grey winter days.
He suggests opting for classic sweet basil, occasionally labelled as Genovese basil, explaining: “I’ve chosen that because it’s very versatile, very reliable and the seeds are generally very cheap so I can make multiple sowings throughout the winter without breaking the bank. He adds practical guidance for planting: “Again, use well-sifted all-purpose compost, ideally in four-inch pots.
“Sprinkle the seeds fairly thinly, and cover with just a tiny amount of additional compost.” To avoid disrupting his carefully arranged seed layers, Benedict employs a mister for watering. After thoroughly moistening the soil, he advises covering the pots to retain moisture levels.
Describing the next crucial step, he notes: “To help them germinate, on goes a bit of clear plastic. What this will do is create a lovely humid environment in there that will just help them to germinate and grow.”
As with previous recommendations, during this period of the year, artificial lighting will deliver optimal outcomes.
Venturing into your garden might provide the perfect counterbalance to those extended festive afternoons spent indoors watching television in a warm, airless living room.
Plus, if you’re fortunate enough to own a greenhouse, it offers an excellent sanctuary should family visitors begin to overstay their festive welcome.
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