Eating Nasturtium: Leaves, Flowers and Pickled Seed Pod Capers

The whole plant tastes of pepper

Nasturtium belongs to the same broad family as mustard and watercress, and the heat you taste in the leaves is the same class of compound. Leaves are the hottest, flowers are mild and slightly sweet with a peppery finish, and the green seed pods are the sharpest of all, closer to horseradish than to pepper. The heat rises in hot dry weather and in older growth.

Nothing needs cooking. Leaves and flowers go straight into a salad, the flowers stuffed with soft cheese, the leaves shredded through a potato salad or blitzed into a pesto in place of some of the basil. Cooking destroys the heat almost entirely, so add them at the end if you use them hot at all.

The heat is strongest raw and fades within a few hours of chopping. Dress leaves at the table rather than in advance.

Picking leaves and flowers without spoiling the plant

Nasturtium regrows fast, so the limit on picking is not what the plant can stand but what tastes good. Take leaves from the outside of the mound where they get most light, choosing ones the size of a coin to the size of a plum. Anything larger than your palm has usually gone tough and very hot.

Flowers are best picked in the morning, before the sun has been on them and before the pollen beetles get inside. Pick the whole flower with an inch of stalk, hold it upside down and tap it to clear any insects, and use it the same day. A flower cut in the afternoon collapses within an hour.

1. Take from the edges, not the middle Picking around the outside keeps light and air in the center of the plant. Stripping the middle leaves the crown exposed and encourages slugs into the gap.
2. Do not wash unless you must Water flattens the flowers and makes leaves limp. Shake off dust and check underneath for blackfly instead. If you do rinse, do it in cold water and dry immediately.
3. Store leaves like salad, flowers on a plate Leaves keep two or three days in a bag in the fridge. Flowers do not keep at all in a bag: lay them in a single layer on a plate under a damp cloth and use within a day.
4. Check every leaf before it goes in a bowl Blackfly cluster on the leaf stalks and the underside of the leaf. Turn each one over. This is not optional with nasturtium.

Picking the green seed pods

After each flower fades it leaves a small green cluster, usually of three ridged segments, sitting where the flower was. Those are the capers. Pick them when they are the size of a pea and still soft enough to dent with a thumbnail. Left another week they go pale, hard and woody, and no amount of pickling will soften them.

Pods start appearing a week or two after flowering begins and keep coming until the frost. A single good plant gives a handful every few days, which is not much at once, so most people collect over a fortnight in a jar of brine in the fridge and pickle the lot when they have enough.

1. Pick every two or three days Pods harden quickly in hot weather. Go over the plants twice a week and take everything that is still soft, whether or not you have enough to pickle yet.
2. Separate the segments The cluster splits into three individual pods. Rub them apart between your fingers and pull off the short stalks, which stay tough after pickling.
3. Hold them in brine while you collect Drop each picking into a jar of salted water in the fridge, one ounce of salt to a pint (25 g to 500 ml). They will keep there for two weeks while you build up a batch.
4. Reject anything pale or hard A pod that has started going straw colored, or that will not dent under a thumbnail, is past it. Leave those on the plant and let them ripen into next year's seed.

Green pods are only worth picking from plants you have not sprayed. This is another reason to deal with blackfly by hand or with a jet of water rather than with anything chemical.

Pickling the pods as capers

The method is a salt brine to draw water out, then a vinegar pickle to keep them. Salting first is what stops them going soft and hollow. The result is not identical to a real caper, which comes from an unrelated Mediterranean shrub, but it is sharper and more peppery and does the same job in a sauce or on fish.

Leave them at least a month before opening. Straight after pickling the raw mustard heat dominates and they taste harsh; after four to six weeks it settles into something rounder. Sealed jars keep a year in a cool dark cupboard, and once opened they last a couple of months in the fridge.

1. Brine for twenty-four hours Cover the pods with a strong brine, about two ounces of salt to a pint of water (50 g to 500 ml), and leave overnight at room temperature. This firms them and draws out the water that would otherwise dilute the vinegar.
2. Rinse and dry Drain, rinse under cold water and pat dry on a cloth. Skipping the rinse leaves them far too salty to eat straight from the jar.
3. Pack with the flavorings Pack into a small sterilized jar with a bay leaf, a few black peppercorns and a thin slice of garlic or a strip of lemon peel. Do not overfill: the pods must stay submerged.
4. Cover with hot vinegar and seal Bring white wine vinegar or cider vinegar just to the boil, pour it over to cover the pods completely, and seal while hot. Any pod above the surface will go moldy and spoil the jar.
5. Label with the date and wait Write the date on the lid and put the jar away for at least a month. Opened early they taste raw and aggressively hot.

Use vinegar of at least five per cent acidity and keep the pods fully covered. If the liquid drops below the top of the pods after a few days, top the jar up with more vinegar rather than water.

What to do with a glut, and what not to do

Nasturtium does not dry or freeze usefully. Dried leaves lose all their heat and taste of nothing but hay, and frozen leaves and flowers thaw as a slimy mush. Everything except the pickled pods has to be used fresh, which is why the pods matter so much as a way of keeping the crop.

For a heavy pick of leaves, the practical route is a pesto or a green sauce, made the same day and kept a few days in the fridge under a film of oil. Flowers can be laid over a cake or a salad, floated in a drink, or stirred into softened butter, but again, that day or the next.

Nasturtium is hot enough that a large amount raw is unpleasant rather than harmful. Treat it as a seasoning leaf, a handful at a time, rather than as the base of a salad.