Gadenin日本語Get the appSmall and hard beats big and soft
An autumn-sown broad bean at three to six inches (8 to 15 cm) with four to six leaves will take temperatures down to about 14F (minus 10C) without protection. The same variety at ten inches (25 cm), grown on by a mild autumn, is soft, hollow-stemmed and top-heavy, and a hard freeze splits the stem at the base. Size going into winter, not cold tolerance, is what decides whether the row survives.
This is why the autumn sowing window is defined by frost rather than by a date. Sow about six weeks before you expect your first hard frost. Sow earlier and the plants get too large. Sow much later and they go into winter as ungerminated seed sitting in cold wet soil, which rots.
If a mild autumn has run your plants up taller than you wanted, do not cut them back. Earth up soil around the base to two or three inches (5 to 8 cm) instead. That supports the stem, insulates the crown, and gives the plant a second place to root from if the top is damaged.
Frost damage on broad beans usually shows as blackened, water-soaked leaf edges after a thaw. The plant almost always regrows from the crown. Do not pull a row that looks dead in midwinter until you have scratched the base and seen whether the growing point is still firm and green.
Drainage kills more overwintered beans than cold
The common cause of losing an autumn row is not freezing but standing water. Roots in saturated cold soil suffocate and rot, and the plant sits looking sullen and yellow for weeks before it collapses in a thaw. Ground that puddles for more than a few hours after rain is not ground to overwinter beans on.
Raise the bed three to four inches (8 to 10 cm) if you can, or ridge soil along the double row so water drains off it. Avoid heavy mulches directly against the stems: straw or leaves piled on the crown hold water there and cause exactly the rot you are trying to prevent. Mulch between the rows, not over the plants.
Also consider wind. A row that is rocked back and forth all winter opens a funnel-shaped hole around each stem, water collects in it and the crown rots. A temporary windbreak on the exposed side, or simply earthing up, fixes it.
| Winter problem | How it looks | What to do |
|---|---|---|
| Waterlogging | Yellow lower leaves, plants loose in the ground, sour-smelling soil | Ridge or raise the bed, cut a drainage channel, do not replant beans there |
| Frost damage to leaves | Blackened water-soaked leaf margins after a thaw | Leave it alone. New growth comes from the crown in early spring |
| Wind rock | A widened hole around the stem base, plants leaning | Earth up two to three inches (5 to 8 cm) and add a windbreak |
| Pigeon damage | Leaves stripped to ragged stubs, droppings on the row | Net the row. Pigeons hit hardest in hard weather when other food is gone |
| Mice and voles | Whole gaps in the row, seed coats or chewed stems at soil level | Net or start next year's row in modules and transplant |
Cloches, row cover and when protection is worth it
In most temperate climates an autumn-sown row needs no protection at all, and covering it does harm: warmth under row cover pushes soft growth that then gets damaged the moment you uncover it. Protection is worth adding only for a forecast cold snap well below the plant's tolerance, and it should come off again as soon as the snap passes.
If you do cover, use a single layer of row cover laid loosely and weighted at the edges, or a cloche with the ends left open on mild days. Both are there to break wind and stop desiccating freeze, not to keep the crop growing. A plant that carries on growing through winter is a plant that will be too big in spring, and it will have used its reserves before it needs them.
Snow is a help, not a threat. A few inches of snow insulates the row and beans come through it well. Brush snow off cloches so they do not collapse, but leave it on the ground.
- Check the crowns after each thaw Pinch the growing point between finger and thumb. Firm means alive. Soft and brown means that plant is gone, and you should pull it so it does not rot next to a healthy neighbor.
- Firm plants back in after a freeze-thaw Frost heave lifts plants and leaves the roots in air. Press each lifted plant back down with your heel and add soil over the exposed roots the same day.
- Keep the row weed free but do not dig Hand pull weeds. Hoeing near overwintered beans cuts surface roots and opens the soil to more water, both of which matter more in winter than in summer.
- Do not feed until growth restarts Nitrogen applied in winter is washed away and encourages soft growth on any plant that responds. Wait until the plants are visibly extending in spring, and even then compost is enough.
The spring restart
Overwintered broad beans sit motionless for weeks and then move suddenly once soil temperature rises past about 45F (7C). That restart is the moment to act. Clear any winter row cover, hoe the weeds off between the rows, and put in the string supports before the plants get tall enough to need them, because running string past a row of tangled plants is a miserable job.
Count the survivors and fill gaps if you can. Gaps of more than about 18 inches (45 cm) are worth filling with a spring sowing or a module-raised plant, which will crop a few weeks after the overwintered ones and extend your picking. Smaller gaps do not matter, since neighboring plants branch out to fill the space.
Overwintered plants often throw several stems from the base where spring-sown plants throw one or two. Leave them. Each stem carries pods, and a well-rooted overwintered plant has the resources to fill them. This is where the earlier harvest and the higher yield of autumn sowing actually comes from.
What to record over winter
Write down the date of the first hard frost, the lowest temperature you saw, and how many plants out of the row survived. Over two or three seasons this tells you your real local limit far better than any hardiness figure printed on a packet, and it lets you decide honestly whether autumn sowing is worth doing where you garden.
Note the date growth restarted in spring and the date the first flower opened. The gap between those two, compared with your spring-sown row, is the whole argument for overwintering, and it is worth having in numbers rather than in memory.