Gadenin日本語Get the appWhat blanching does and whether you need it
Blanching means keeping light off the stalks for the last few weeks of growth. Without light the plant stops making chlorophyll in those tissues, so the stalks turn from green to cream, lose most of their bitterness and become noticeably more tender. The change is real and it happens quickly, over three to five weeks.
Whether you need to do it depends on the type you are growing. Traditional trench celery is bred to be blanched and is genuinely harsh eaten green. Self-blanching types have been selected to be mild without the work, and grown in a close block they shade each other enough for most tastes. Green cutting types are meant to be eaten green and blanching them is a waste of effort.
So decide before you plant, because the decision changes the spacing and the depth you plant at, not just what you do in autumn.
| Type | Needs blanching | How it is grown |
|---|---|---|
| Trench types | Yes, or the stalks stay strong flavored | Planted in a trench and earthed up in stages |
| Self-blanching types | Optional, a collar improves them | Close block planting, plants shade each other |
| Green cutting types | No | Normal spacing, cut stalks as needed |
Blanched stalks are more tender but also more perishable and slightly lower in flavor compounds overall. If you like a strong celery taste for cooking, blanch less and cut earlier.
When to start
Start when the plants are roughly twelve inches (30 cm) tall and clearly growing strongly, and count on three to five weeks from the first earthing up to harvest. Earlier than that and you are covering a plant that still needs its lower leaves to build size. Later and the weather turns before the stalks have paled.
Never blanch a plant that is struggling. Covering the stems reduces the leaf area doing the work, so a plant already checked by drought or cold simply stops. Sort out the watering first, give it a fortnight, then start.
- Check the plant is ready Twelve inches (30 cm) or more of stalk, thick at the base, with new leaves still coming from the center. A plant that has not grown in the last fortnight is not ready whatever its height.
- Water the day before Earthing up dry soil around a dry plant traps that dryness against the stems for weeks. Soak the bed thoroughly and let the surface drain before you start.
- Tie the stalks loosely together A soft tie around the middle of the plant holds the stalks upright and keeps soil out of the heart. Tie it snug enough to hold, loose enough not to bruise.
- Draw soil up to a third of the height Pull fine, crumbly soil up around the plant to cover the bottom third of the stalks. Keep it off the leaves entirely. Soil on leaves rots them and the rot spreads down into the stalks.
- Repeat every two to three weeks Two or three rounds, each adding a few more inches, until only the top rosette of leaves is showing. Doing it in stages rather than all at once is what keeps the plant growing throughout.
Collars instead of soil
On heavy soil, in a raised bed, or if you simply do not want grit in your celery, a collar does the same job with less mess. Wrap the lower two thirds of the plant in thick brown paper, cardboard or black plastic, tied top and bottom, leaving the leaves free.
Collars blanch more evenly than soil because the covering is uniform and they let you inspect the plant by untying rather than digging. The trade-off is that a collar traps still, humid air against the stalks, so slugs move in and rot starts more readily in wet weather. Untie one plant every week or so and look.
Whichever method you use, the covering must exclude light completely. A partly shaded stalk goes an unappealing streaky yellow-green rather than clean cream, and the tough tissue stays tough.
Do not use anything that holds water against the stems. Newspaper collapses into a wet sleeve after a fortnight of rain and rots the plant it was supposed to protect.
What goes wrong, and what to record
The three common failures are all timing errors. Soil in the heart, from earthing up carelessly or without a tie, gives you a rotten center and a plant that has to be thrown away. Blanching a checked plant produces pale stalks that are still stringy, because paleness and tenderness are separate things and only fast growth delivers the second. And starting too late leaves you harvesting green stalks in the first frosts.
Slugs are the other constant. The dark, damp space you have just created around the base of the plant is ideal for them and they will hollow out stalks from the inside without any sign on the outside. Check under collars and at the base of earthed-up plants regularly.
Write down the date of each earthing up, how high you took it, and the date you cut the first plant. After one season you will know how many weeks your own site actually needs, which is worth more than any general figure. Note the position of any plant that rotted too, because rot usually clusters at the wet end of a bed and that tells you where not to plant next year.