A large bag of kale can be far more than you need for one meal. Leave it in the fridge too long and the edges become limp or yellow before you get through half. Freezing allows you to keep it for later cooking, but the method is different from simply putting raw leaves into a bag.
The National Center for Home Food Preservation recommends blanching most greens before freezing. That short heat treatment helps retain colour and flavour during storage. Once you have blanched, cooled and portioned the leaves, frozen kale becomes an easy addition to winter soups, pasta sauces and casseroles.
Pick sound, fresh leaves
Choose kale that is firm and fresh for its variety. Curly kale may have textured dark green leaves; other kinds can be smoother or purple.
Avoid bunches that are already slimy, mouldy or strongly decayed. Freezing slows deterioration; it doesn't make poor-quality produce fresh again.
Remove tough yellowed sections and inspect between the folds for soil and small insects, especially when the leaves came from a garden.
Wash thoroughly before freezing
Fill a clean bowl with cold drinking water, loosen the leaves gently and lift them out so grit can remain in the bottom. Finish by rinsing under running water.
You may need to repeat with particularly sandy kale. Don't rely on a single quick sprinkle of water over a tightly packed bag of leaves.
The Food and Drug Administration advises cleaning produce with running water rather than household soap or detergent. Wash your hands and equipment as well.
Remove the thickest stems
The central rib of mature kale can be tough. Fold a leaf gently and strip the blade away from the thickest stem, or cut alongside it with a knife.
Small tender leaves may need less trimming. Keep any edible sound stems for finely chopped soups or other suitable cooking, rather than automatically throwing everything away.
Tear or cut the leafy portions into sizes you'll actually use later. Smaller pieces fit conveniently into soup and sauce portions.
Why blanch kale first?
Enzymes within vegetables can continue affecting colour, flavour and texture during frozen storage. Brief heating slows or stops many of these reactions.
The National Center's guidance for freezing greens recommends water-blanching most greens for two minutes, while collards require three minutes.
That is a tested quality-preservation method. Skipping it may save a few minutes today but lead to less appealing kale after extended storage.
Prepare a large pot of boiling water
Bring plenty of water to a vigorous boil in a large saucepan. Set up a separate bowl of ice water beside it before adding any leaves.
The National Center recommends enough water that it returns to the boil promptly after vegetables are added. Overloading a small pan with a giant heap of cold kale undermines timing.
A wire basket or large slotted spoon makes lifting the leaves safer. Avoid splashing boiling water while pushing bulky foliage under the surface.
Blanch for the recommended time
For kale treated under the National Center's 'other greens' category, use two minutes of water blanching after the water has returned to boiling.
Work in modest batches rather than compressing every leaf into the pot. The greens will wilt and reduce substantially in volume.
Keep the heat steady and follow the source's timing method, not merely the moment the water first approaches a simmer.
Cool it promptly
Move the blanched kale directly into ice water. The aim is to stop cooking so the leaves do not become excessively soft.
Replace ice as needed between batches. Water that becomes warm won't cool new leaves effectively.
Once the kale has cooled, lift it out and drain. Don't leave cooked greens sitting at room temperature for hours before packaging.
Squeeze out excess water
Place cooled kale in a colander and press gently to remove water. You can also wrap small portions in a clean towel or squeeze carefully by hand.
Removing excess liquid reduces large ice crystals and helps avoid a freezer bag full of water. The leaves will still contain moisture, and they don't need to be dried like salad leaves.
Portion before squeezing into very tight balls. A dense giant frozen lump may be difficult to divide when you want only a handful.
Portion for the meals you actually make
Consider one small bag for a pot of soup, another for pasta sauce and a few individual portions for smoothies if you use cooked greens that way.
Pack into suitable freezer bags or containers, leaving appropriate headspace and removing excess air. Label the contents and freezing date.
A bag containing finely chopped frozen kale can look remarkably similar to other greens after a few months, so a clear label saves guesswork.
Should you freeze it flat?
A flat freezer bag can stack neatly and allow you to break off smaller sections. Spread the drained leaves evenly instead of sealing one thick ball in the centre.
For easy separate pieces, you can spread cooled drained kale on a tray to freeze until firm and then bag it, though small leaves may still stick together.
Whatever the method, freeze promptly at the proper freezer temperature instead of leaving portions on the worktop while sorting other groceries.
Can raw kale be frozen?
Some people freeze raw kale for short-term smoothie use, but the National Center's general advice recommends blanching leafy greens to protect quality during frozen storage.
Raw leaves may suffer stronger flavour, colour and texture changes. They may also contain soil unless cleaned carefully first.
For a guide intended to give a dependable all-round result, blanching, cooling and packing is the method worth recommending.
Use frozen kale in cooking
Frozen kale is convenient in soups, stews, curries, pasta sauces and vegetable bakes. The leaves have already wilted, so you can stir a portion in near the end and heat it thoroughly.
The National Center advises that leafy greens sometimes heat more evenly when partially thawed. Follow a suitable recipe and separate clumps before serving.
Frozen kale won't recreate the crisp texture of fresh leaves in a raw salad. Freezing disrupts cell structure, and it is better used where tenderness is welcome.
What about smoothies?
Kale is commonly added to smoothies, but if you've frozen it after blanching the flavour and texture will differ from raw fresh greens.
Use clean equipment and follow food safety guidance for the other ingredients, especially dairy products and perishable fruit. Don't assume freezing makes an unsafe ingredient sterile.
Start with a small portion and adjust. Blanched kale can have a pronounced vegetal flavour when blended with sweet fruit.
How long can it be kept?
The exact quality period depends on packaging and freezer performance. A consistently cold freezer and tightly sealed bags preserve the result better than repeated temperature fluctuations.
Inspect for excessive frost, drying or off-odours when using stored vegetables. Use older batches first so they don't remain forgotten for years.
Keep the freezer around its recommended -18°C setting and avoid stuffing warm freshly blanched food into one tightly packed section before it can freeze.
Mistakes that cause soggy results
Overblanching, failing to cool rapidly and packaging lots of water with the leaves can all make thawed kale excessively wet.
For a dish that needs less moisture, squeeze thawed kale gently before adding it. In soup, the extra water usually matters much less.
If a package has become one giant block, plan smaller portions next time rather than hacking at the frozen leaves with a sharp knife.
The practical method
Wash and destem sound leaves, blanch in boiling water for two minutes, cool immediately, drain well and freeze in labelled portions.
The result won't behave like fresh salad kale, but it makes a useful freezer ingredient for meals where cooked greens belong.