Gadenin日本語Get the appTwo crops, two calendars
Florence fennel occupies the ground for about twelve to fourteen weeks and then leaves. The whole calendar for it sits in the second half of the year: sow after midsummer so bulbing happens in shortening days, keep growth unchecked, earth up, and cut before the first hard frosts. Nothing about it carries over into the next season except your notes.
Herb fennel runs on an annual cycle instead. It emerges from the crown in early spring, makes leaf, flowers in high summer, ripens seed in early autumn and dies back to the crown for winter. Your jobs are spread across that cycle and most of them are about limiting it: cutting back for fresh leaf, staking before it flops, and deadheading before it seeds.
Kept side by side, the two calendars rarely clash. The busy period for the bulb crop is late summer and early autumn, which is exactly when herb fennel needs deadheading, so a single walk down the bed covers both.
| Stage | Trigger to start | Main jobs | Decision to make |
|---|---|---|---|
| Herb fennel wakes | Shoots push from the crown in early spring | Stake beside the crown, clear old stems away | Whether this plant stays another year |
| Herb fennel cut back | Plants 18 inches (45 cm) tall in late spring | Cut whole plant to 4 inches (10 cm) for a dense leaf flush | Leaf crop this year, or let it run to seed |
| Bulb sowing 1 | Around the longest day, soil above 60F (15C) | Direct sow a half inch (1 cm) deep into moist ground | Which bed, keeping 3 years since the last umbellifer |
| First thinning | First true feathery leaf | Snip to 4 inches (10 cm), slug watch, hand weed only | Whether the row is thick enough to keep all of it |
| Bulb sowings 2 and 3 | Every 3 weeks after the first | Repeat sowing, last one 12 weeks before hard frost | How much fennel you will actually eat |
| Second thinning | Plants 5 inches (13 cm) tall | Snip to final 8 to 10 inches (20 to 25 cm) | Nothing, do it on time regardless |
| Herb fennel flowering | Umbels open bright yellow in high summer | Take pollen from open heads, leave some for hoverflies | How many heads to let ripen for seed |
| Bulbs swelling | Base the size of a golf ball | Earth up every 10 days, water steadily, stop feeding | Whether growth was checked, so expect bolting |
| Herb fennel seed | Half the seeds on a head turn gray-brown | Cut heads into paper bags, deadhead everything else | How much seed you actually need |
| Bulb harvest | Bulb 3 inches (7.5 cm) across and firm | Cut an inch (2.5 cm) above soil, trim fronds off | Cut now or risk splitting and bolting |
| Second flush | 2 to 3 weeks after cutting | Water the stumps, cut shoots at 6 inches (15 cm) | Whether to clear the bed or keep cutting shoots |
| Clear up | After the first hard frost | Pull bulb plants and debris, cut herb fennel to the crown | Which volunteer seedlings to remove now |
Spring: herb fennel only, and resisting the bulb sowing
Spring belongs to herb fennel. The crown pushes new shoots as soon as the soil warms, and the stake should go in while the plant is still knee-high, because driving one in later damages the root and a leaning plant never straightens. Clear last year's dead stems away from the crown rather than leaving them; they carry disease spores into the new growth.
Late spring is the moment to decide what the plant is for. Cutting it right down to 4 inches (10 cm) delays flowering by several weeks and produces a shorter, denser flush of fine fronds, which is the best leaf the plant will ever give you. Left uncut it will make height and flower, which is what you want only if you are after pollen and seed.
The temptation in spring is to sow Florence fennel because the seed packet is in your hand and the weather is good. Resist it, or sow it knowingly as a leaf crop. Lengthening days and cold nights are the two strongest bolting triggers, and a spring sowing almost always throws a flower stem at eight inches (20 cm) tall with no bulb at all.
Midsummer into autumn: the bulb season
From around the longest day the conditions finally suit Florence fennel: warm soil above 60F (15C) and days that are shortening rather than lengthening. Sow direct into ground already watered, thin early with scissors, and start the succession so that a short row goes in every three weeks. The last useful sowing needs about twelve weeks of growing weather before hard frost.
Once the bases begin to swell, the routine is fixed: steady water so the plants never wilt, earthing up every ten days, hand weeding only, and no more feeding. This is also when herb fennel is at its tallest and in full flower, drawing hoverflies and parasitic wasps that keep aphid numbers down across the whole bed. Leave those umbels standing until you have taken what you want from them.
Autumn brings both harvests together. Cut bulbs at tennis-ball size, an inch (2.5 cm) above the soil so the stumps regrow, and take herb fennel seed heads into paper bags as soon as half the seeds on a head have colored. Deadhead everything you are not harvesting; a head left to shatter is next spring's weeding.
- Sow the last bulb batch 12 weeks before hard frost Count back from your usual first hard frost. Later sowings will grow good fronds but will not have time to swell a base, and a light frost on a mature bulb does no harm.
- Walk the bed weekly once bulbs start swelling One pass covers the whole job: check for wilting, earth up any bulb that has grown, pull weeds by hand, and look for stems starting to extend so you can cut those plants for fronds instead.
- Cut every herb fennel umbel you are not saving Do this as the petals fade and before the seed browns. Green umbels can go on the compost pile safely; browning ones cannot, because the seed on them is already viable.
- Take the pollen while heads are fully open Cut open yellow umbels in dry morning weather, hang them in paper bags for a few days and shake. The pollen that falls is the strongest flavor the plant produces and it stores for a year.
Winter, and setting up next season
After the first hard frost, pull the Florence fennel plants entirely, roots and all, and take the debris off the bed. Umbellifer disease spores overwinter on dead stems, and leaving them is the commonest way a clean bed becomes a problem bed. Cut herb fennel down to the crown at the same time and remove the material rather than mulching with it.
Herb fennel is fully hardy in most gardens and needs no protection; it simply disappears and returns from the crown. Winter is the easiest time to remove a plant you no longer want, because the ground is damp and there is no top growth in the way. Fork a wide circle, lift the whole taproot, and sift the hole for fragments, since any piece of crown left behind will regrow.
Finish by writing the season down while it is still fresh. Record each bulb sowing date against its harvest date and whether it bulbed or bolted, note which bed each crop occupied so you can keep three years between umbellifers, and mark where herb fennel plants stand and where volunteer seedlings appeared. Those three notes are what turn fennel from a crop that unpredictably refuses to bulb into one you can plan with confidence.
The two numbers worth having are days from sowing to a usable bulb in your own garden, and the proportion of each sowing window that bolted. After two seasons they tell you exactly when to sow and how much.