Rhubarb: How to Harvest, Prep and Cook It, Step by Step

Rhubarb (Rheum rhabarbarum) is a perennial vegetable that we use like a fruit because of its distinctly tart flavour. Only the thick stalks are edible – they're where the sourness comes from (mainly malic and oxalic acid), giving rhubarb that bright, tangy edge. That tartness balances beautifully against sugar, which is why rhubarb works so well in pies, compotes, syrups and even savoury sauces for meat.

It originally comes from Asia, from the region that is now China and Tibet, where historical sources suggest it was used as a medicinal plant thousands of years ago. It didn't reach Europe until the 17th century, and only there did it become a proper kitchen ingredient. Flavour-wise, it pairs beautifully with strawberries, apples and vanilla – the sweetness of the fruit rounds out its sharpness, so you need less added sugar.

Harvest rhubarb from April through June, when the stalks are at their juiciest. Well-watered plants can start producing as early as March and keep going into summer. Pick it gradually rather than all at once – that way the plant keeps producing right through spring.

You can tell rhubarb is ready by the length and firmness of the stalk, not its colour – harvest stalks that are at least 25–30 cm long, firm and crisp enough to snap. The common belief that green stalks are unripe is a myth: colour is mostly down to variety and has little bearing on ripeness or flavour (red varieties just tend to be a touch sweeter and look prettier baked into a pie). Only take a third to half of the stalks from each clump so the plant has enough left to keep growing. Once a flower stalk starts to shoot up, the plant's energy shifts to flowering and the stalks turn woody and bitter – snap the flower stalk off right away and wind down harvesting for the season.

Don't cut rhubarb with a knife – twist it out instead. Grip the stalk near the base, give it a gentle twist, and pull upward to release it from the crown. Cutting at ground level leaves a stump that can easily rot; a cleanly twisted-out stalk leaves no wound and encourages further growth. Snap off the leaves right there and leave them in the garden – we'll explain why below.

Prepping rhubarb comes down to three steps: wash the stalks, remove the leaves, and chop the stalks into 1–3 cm pieces. Usually that's all you need to do.

• Washing: rinse the stalks under running water, scrubbing off any dirt with a soft brush, then pat them dry. Rhubarb grows low to the ground, so it's often muddy.

• Peel it, or not? Young, thin spring stalks don't need peeling – the skin is delicate and holds its colour well. For thick, stringy late-season stalks, use a sharp knife to strip off the tough outer fibres, or you'll end up with chewy strands in your dish.

• Chopping: cut the stalks crosswise into 1–3 cm pieces, depending on the recipe. Smaller pieces break down into a sauce or compote, while larger chunks hold their shape in a pie.

To keep a rhubarb pie from turning watery or overly sour, watch two things: moisture and sugar ratio. Toss the chopped rhubarb with sugar and let it sit for 20–30 minutes to draw out the juice (macerating); then either drain that juice off or thicken the filling with a spoonful of starch (cornflour or potato starch) so it doesn't soak the base. Balance the tartness with sugar – for 500 g of rhubarb, 80–120 g is usually enough, depending on how sweet your pastry is. It pairs wonderfully with strawberries, raspberries, vanilla and a pinch of cinnamon. Bake at around 180°C until the pastry turns golden and the filling starts to bubble.

For exact ratios and method, though, stick to tried-and-tested recipes – here are a few of our favourite rhubarb bakes:

Rhubarb is naturally light – about 20 kcal per 100 g – and, according to nutritional data, a good source of fibre, vitamin K and antioxidants; a single cup of cooked rhubarb covers a significant chunk of your daily vitamin K needs. What usually makes it "unhealthy" is the amount of sugar used to sweeten it. Here are a few ways to cut back:

• Sweeten with fruit instead of sugar: simmer ripe strawberries, pear or apple together with the rhubarb – the fruit's natural sweetness tones down the tartness.

• Use natural sweeteners in moderation: honey or maple syrup add flavour, but treat them like sugar, not as an unlimited "healthy" swap.

• Steam it: steam rhubarb pieces for 5–7 minutes. It keeps more colour and nutrients this way, and works well as a light side for fish or tossed into a salad.

• Sugar-free compote or purée: simmer rhubarb briefly with a little water and vanilla – lovely with yoghurt, curd cheese or on pancakes.

For a lighter gluten-free or vegan option, try it as a smoothie: blend a handful of rhubarb with strawberries and a plant-based milk. And if you want a dessert that doesn't feel heavy, go for a soufflé:

The best way to keep rhubarb is to freeze it – raw, chopped pieces keep in the freezer for 6–12 months, and you can use it straight from frozen in pies or compotes, no need to thaw.

• Freezing: spread 2–3 cm pieces in a single layer on a baking-paper-lined tray and flash-freeze for 1–2 hours. Then transfer to bags or containers and label with the date – this way the pieces won't clump together and you can take out exactly as much as you need. No need to blanch first.

• In the fridge: fresh, unwashed stalks wrapped in a tea towel or bag will keep for about a week.

• Drying: dry thin slices in a dehydrator or oven at around 50°C for several hours, until crisp. Store in an airtight jar away from light; great in granola, tea blends or baking.

You can also lock rhubarb's flavour in for months by turning it into syrup, compote or jam.

Rhubarb leaves don't belong on a plate – but they're great for the compost heap. They're toxic, yes, but they break down easily and enrich compost beautifully. The oxalic acid breaks down during decomposition, so the finished compost won't harm your plants; feel free to chop up the leaves and toss them onto the pile.

You'll also sometimes hear that a leaf infusion makes a good aphid spray, but its effectiveness isn't well proven, and the liquid from the leaves is toxic to you too – it's best avoided on anything you plan to eat. If you're handling a large amount of leaves, wear gloves and keep them well away from children and pets.