When to Harvest Romanesco: Cutting Before the Spiral Goes

Judge by the cones, not by the size

The habit that costs people their romanesco is waiting for a head to reach the size they have seen in a shop. Head size is set by the plant, not by patience. A plant that built a modest canopy makes a five inch head and then starts to open, and waiting only turns a good five inch head into a poor one.

The test is geometry. Look at the individual cones. On a head at its peak they are sharply pointed, tightly packed against one another, and the spiral runs clean from the outer ring to the center with no gaps between the sections. Press the head gently with the flat of your hand and it resists like a firm cabbage.

As soon as the cone tips begin to look rounded, or you can see daylight down between the sections, the head is past its best and going backwards daily. Typical home garden heads run four to eight inches (10 to 20 cm) across, and a well-grown plant on wide spacing can exceed that.

Once the head is expanding, check every two days. Romanesco has a shorter window at its peak than either cauliflower or calabrese, and three days of neglect in mild weather can be enough to lose the spiral entirely.

How to cut

Cutting is simple, but doing it in the cool of the morning and leaving the wrapper leaves attached makes a real difference to how long the head stays crisp. Field heat is what shortens storage life, and a head cut in the afternoon sun is already warm and limp before it reaches the kitchen.

1. Cut early in the morning A head cut before the sun is on it comes in cold and firm and keeps several days longer than the same head cut at midday.
2. Cut the stem below the lowest wrapper leaves Take a sharp knife to the main stem two or three inches (5 to 8 cm) below the head, so it comes away with a collar of leaves around it.
3. Leave the wrapper leaves on until you cook it They protect the cone tips from bruising, which on a romanesco is the difference between a head that still looks like a romanesco and one that does not.
4. Turn the head over and look Slugs and caterpillars shelter between the wrapper leaves and the base of the head. Check in the garden, not in the kitchen sink.
5. Carry it upright, not stacked The cone tips crush under the weight of another head. Set them stem-down in a box in a single layer if you are cutting several.
6. Decide whether the plant stays If you want side shoots, leave the plant with plenty of stem and leaf. If you do not, pull it now, knock the soil off the roots and inspect them for the swollen knobs that mean clubroot.

The stem of a romanesco is thick, sweet and good eating, more so than a cauliflower stem. Peel the tough outer layer off and use the core; do not throw the four inches below the head away.

Side shoots after the main head

Romanesco sits between a cauliflower and a sprouting broccoli in this respect. After the main head is cut, plants that still have plenty of leaf and a mild autumn ahead of them will often push out small side shoots from the leaf axils over the following weeks. They carry the same spiral in miniature, an inch or two across, and they are excellent.

They are a bonus rather than a plan. Cut the main head high, leaving as much stem and leaf as you can, water the plant and give it a single light nitrogen feed. If nothing shows within three weeks, or hard frost arrives, pull the plant and free the ground.

Do not leave spent plants standing all winter on the chance of side shoots. They occupy a large amount of space, shelter aphids and caterpillars through the cold, and keep soil-borne brassica diseases active in that spot.

Keeping romanesco after cutting

Romanesco keeps a little better than broccoli and about as well as cauliflower, which is to say not long. It wants cold, damp air, and it must be kept away from ripening fruit, because the ethylene those give off yellows and softens the head within days. The realistic plan is to eat it within a week and freeze whatever you cannot.

Break a head into its natural cones rather than chopping across it. Each cone comes away whole from the base and keeps the spiral form, which is most of the reason to grow this crop rather than a cauliflower.

Spreading a harvest that wants to arrive at once

Romanesco is triggered by the same cool weather across the whole bed, so identical plants sown on the same day will all head within about a week of each other. On a crop that has occupied the ground since late spring, losing half of it to a glut is an expensive way to finish the season.

Spread it deliberately. Two or three sowings a fortnight apart help, though less than they would on a faster crop, because the cool weather pulls the later ones forward. Position does more: a few plants in a cooler, shadier part of the plot head noticeably earlier, and a few in the warmest corner run later.

1. Sow in two batches a fortnight apart The gap narrows by harvest because both respond to the same cooling weather, but a week of separation at cutting is still worth having.
2. Use the cool and warm corners of the plot deliberately Plants on the shaded side reach the heading trigger sooner. Plants against a warm wall run later. This spreads the cutting more reliably than staggered sowing does.
3. Freeze the overlap on the day you cut When heads do collide, break them into cones, blanch and freeze the same day rather than trying to hold whole heads in the fridge.
4. Cut slightly early rather than slightly late A head cut two days early is perfect. A head cut two days late has lost its spiral. When in doubt, cut.

What to note at harvest

Harvest is when every earlier decision finally shows its result, which makes it the most useful moment of the year to write things down. Ten lines noted while you are cutting will shape next season's sowing date far better than anything you try to recall in spring.

Record the position of any plant that headed poorly, not only the fact that it did. Repeated failures in the same corner of a bed almost always come down to drainage, shade or a soil problem in that spot rather than to the season.