When to Harvest Sweetcorn
Home-grown sweetcorn is one of the real treats of late summer. Picked at just the right moment and cooked straight away, it's sweeter and juicier than anything you can buy. The window for perfect cobs is fairly short, though, so it pays to know exactly what to look for.
Quick answer
Sweetcorn is usually ready from late summer into early autumn, when the silks at the tip of the cob have turned brown and dry. To be sure, peel back part of the husk and press a kernel with your thumbnail. If the juice is creamy, the cob is ready. Watery juice means it needs longer, and a thick, doughy paste means it's past its best. Twist the cob sharply downwards to snap it off, and cook it as soon as possible.
When is sweetcorn ready in the UK?
Most sweetcorn planted out in late May or early June is ready from August into September, and later in a cool summer or in the north. Each plant usually produces around two cobs, and they often ripen within a week or so of each other.
The cobs tend to be ready about three to four weeks after the silks first appear, although this varies with the weather and the variety. Check the days to maturity on the seed packet as a rough guide.
How to tell sweetcorn is ready
1. Look at the silks. The tassel of silky threads at the top of each cob starts off pale and fresh. When the cob is nearly ready, the silks turn brown and begin to dry out.
2. Feel the cob. A ripe cob feels plump and firm right to the tip, and the husk is still green.
3. Do the thumbnail test. This is the most reliable check. Gently peel back a little of the husk, without removing the cob, and push your thumbnail into a kernel:
Clear, watery juice: not ready yet. Close the husk back up and check again in a few days.
Creamy, milky juice: perfect. Pick it now.
Thick, doughy paste: overripe. The sugars have turned to starch and the kernels will be chewy.
How to pick sweetcorn
Hold the main stem steady with one hand, grip the cob with the other, and twist it sharply downwards so it snaps away from the plant. Try not to damage the stem, as there may be a second cob on the same plant still ripening.
Cook it quickly
As soon as a cob is picked, the sugars in the kernels start turning into starch, so sweetcorn loses its sweetness surprisingly quickly. For the best flavour, have the pan of water boiling before you go out to pick it.
Supersweet varieties hold on to their sugar for longer after picking, which gives you a little more time, although their kernels can be slightly chewier.
If you have more cobs than you can eat, blanch the kernels and freeze them straight away.
Getting more and better cobs next year
Plant in a block. Sweetcorn is pollinated by the wind, so plants grown in a square block, rather than a single long row, pollinate each other much better. Poorly filled cobs with gaps in the rows of kernels are usually a sign of poor pollination.
Keep supersweet types apart. If supersweet varieties cross with other types, the cobs can lose their sweetness, so grow them away from other sweetcorn.
Water as the cobs swell. Keep plants well watered while the silks are showing and the cobs are filling.
For planting times, see when to plant sweetcorn in the UK
If your plants struggled this year, see why sweetcorn doesn't grow
Harvesting sweetcorn grown in containers
Sweetcorn in tubs ripens at the same time as plants in the ground, and you can use the same checks. Plants in pots usually produce smaller cobs, and because there are fewer plants, pollination can be patchy. Grouping several pots together helps. Our sweetcorn in containers guide explains how to set them up.
The whole season, from sowing to harvest, is covered in how to grow sweetcorn in the UK
Common questions
When is sweetcorn ready to pick in the UK?
Usually from August into September, when the silks have turned brown. Check with the thumbnail test: creamy juice means the cob is ready.
How do you know when sweetcorn is ripe?
The silks turn brown and dry, the cob feels full to the tip, and a kernel pressed with your thumbnail releases creamy, milky juice.
How many cobs do you get per sweetcorn plant?
Usually about two cobs per plant.
Why does my sweetcorn have missing kernels?
Gaps in the rows of kernels are usually caused by poor pollination. Grow plants in a block rather than a single row so the wind can carry pollen between them.
Harvesting and pollination advice based on RHS guidance.