Why Spring Greens Deserve a Place in the Freezer

There is a fortnight in late spring when the garden, the allotment or the veg box seems to conspire against you. The spring greens are suddenly enormous, the kale is threatening to flower, and the purple sprouting broccoli is producing faster than you can eat it. This is the moment to reach for a large pan and a colander, because blanching and freezing is the most straightforward way to keep that sweet, green, just-picked flavour for the months when the only greens on offer have travelled a long way to reach you.

The reason blanching matters is enzymes. Left alone in the freezer, raw greens continue their internal chemistry, just very slowly. Those enzymes break down chlorophyll and vitamins, so after a few weeks you are left with olive-yellow, hay-scented mush. A short spell in boiling water deactivates them. The result, properly done, is a bag of greens that still tastes of spring in November.

What to Blanch, and What to Leave Alone

Almost any tender or leafy green takes kindly to this treatment. The exceptions are the watery salad vegetables, which simply collapse.

• Excellent candidates: spring greens, curly kale and cavolo nero, spinach, Swiss chard, purple sprouting broccoli, calabrese, wild garlic, nettle tops, young leeks.
• Workable with care: asparagus and broad beans, though both lose a little bite. Freeze them only if you have a genuine glut.
• Not worth freezing: lettuce, rocket, watercress, cucumber and most soft herbs. Rocket and cress turn to slime; soft herbs keep far better chopped into oil or butter.

If you are freezing several different greens, keep them in separate batches. They cook at different speeds and you will thank yourself later when you want spinach for a curry and broccoli for a gratin.

Prepping Your Greens Properly

Fill the sink with cold water and wash everything thoroughly, paying attention to the folds where soil likes to hide. Lift the greens out rather than draining the sink, so the grit stays at the bottom. Trim away any yellowing leaves, tough stalks and woody bases.

Cut everything to a roughly even size. Shredded spring greens and kale should be ribbons about a centimetre wide; broccoli wants to be broken into florets no bigger than a walnut. Uniformity is not fussiness — it means every piece blanches in the same time, so nothing ends up half raw and half disintegrated.

Use a pan that is far bigger than you think you need. For every 500g of prepared greens, allow about four litres of water. Salting the water lightly is optional but does help the flavour. Bring it to a fierce, rolling boil before anything goes in.

The Blanch and Ice Bath, Step by Step

Work in small batches. Overloading the pan drops the temperature and the greens effectively stew rather than blanch. Add the greens, push them under with a slotted spoon, and start timing the moment the water comes back to a proper boil.

• Spinach, wild garlic, nettle tops: 1 minute
• Shredded spring greens, chard leaves: 90 seconds to 2 minutes
• Kale and cavolo nero: 2 minutes
• Purple sprouting broccoli, small florets: 3 minutes
• Chard stalks, thick broccoli stems: 3 to 4 minutes

Meanwhile, have a large bowl of iced water waiting — roughly one part ice to two parts water, and plenty of it. The instant the timer goes, lift the greens out with a slotted spoon or spider and plunge them into the ice. This is the step people skip, and it is the one that keeps the colour bright. Leave them in the ice bath for the same length of time they spent in the pan, until they are completely cold to the touch. Top up the ice if it melts away.

Drying, Portioning and Packing

Drain the cold greens in a colander, then dry them properly. A salad spinner is ideal; otherwise spread them over a clean tea towel and pat gently. Surface water is the enemy here, because it turns into ice crystals that shred the cell walls and leave you with a watery, mushy result.

Portion before you freeze. Think about what you actually cook: 200–250g bags suit a family side dish, while 100g portions are handy for soups and pasta. Press each portion into a freezer bag, flatten it, and squeeze out as much air as you can — or suck it out with a straw held at the corner of the bag. Flattened bags stack like files, thaw in minutes and take up a fraction of the space of a lumpy tub.

Label every bag with the contents and the date, then freeze them flat on a tray for an hour before stacking them upright. Use within eight to twelve months, and reach for the oldest first.

Cooking From Frozen

There is no need to thaw. Drop the frozen block straight into boiling water for two or three minutes, or add it directly to soups, stews, curries and pasta sauces in the last few minutes of cooking. A partly thawed portion is good folded through a gratin, a frittata or a pan of bubble and squeak, where a softer texture is exactly what you want.

Be realistic about what changes. Frozen greens will never be as crisp as fresh, so treat them as an ingredient for cooking rather than for a crunchy salad. Never thaw and refreeze, and don't leave a bag sitting warm on the worktop for hours. Treated well, a bag of blanched spring greens is a quiet triumph — a spoonful of April in the depths of a grey January.