Gadenin日本語Get the appCount backwards from the head, not forwards from the sowing
Broccoli makes its best head when average temperatures sit between 60F and 70F (15C and 21C). Everything in the schedule follows from that. Decide which window in your year is reliably in that range, then count back the days to maturity for the plants you have to find the sowing date. That is the whole method.
Days to maturity are counted from transplanting, not from sowing, and run roughly 55 to 85 days depending on the type. Add another four to six weeks for the seedling stage. So a head wanted in the cool part of autumn means transplanting in late summer heat, and a head wanted in late spring means sowing in the middle of winter under cover.
| Working backwards from | Count back | What happens then |
|---|---|---|
| The head you want to cut | 0 | Average temperature 60 to 70F (15 to 21C) |
| Transplanting | 55 to 85 days before the cut | Four to five true leaves, firm bed prepared |
| Sowing | Four to six weeks before transplanting | Cells under cover or in a shaded frame |
| Bed preparation | Two to three weeks before transplanting | Lime, manure, tread firm |
The autumn crop is the easier one
If you can only fit one broccoli crop into the year, make it the one that heads as the weather is cooling. Temperatures fall steadily through the head forming period instead of rising, so the head tightens rather than opening, bolting is almost impossible, and a light frost actually improves the flavor. Mature plants take temperatures down to about 26F (minus 3C) without harm.
The difficult part of an autumn crop is the start: seedlings have to be raised in the heat of late summer, when germination is poor above 85F (29C) and flea beetle is at its worst. Sow in a shaded spot, keep the cells damp, and mesh the tray from the day you sow. Once the plants are in the ground and the weather turns, the crop looks after itself.
- Sow in shade in late summer Keep the tray out of direct sun and water in the morning and evening. Compost above 85F (29C) simply will not germinate broccoli reliably.
- Transplant into moist, firm ground Soak the bed the day before if it is dry. Plants going into hot dry soil sit still for a fortnight, and that delay pushes the head into cold weather.
- Keep the mesh on into autumn Cabbage whites are still laying late in the season, and pigeon pressure rises sharply as other food disappears. Leave the netting on until you cut.
The spring crop needs protection at both ends
A crop timed to head in late spring has to be sown in winter, and that means a heated propagator or a bright windowsill. The risk is the cold-induced bolting described in the seedling notes: a plant with a stem thicker than a quarter inch (6 mm) that meets ten days below 50F (10C) will throw a small head and flower. Keeping the seedlings warm is not a comfort measure, it decides the crop.
At the other end, the head has to mature before summer heat arrives. That window can be narrow, and it is the reason spring broccoli sometimes bolts within days of looking ready. Plan to cut on the early side, and have row cover or shade cloth ready if a warm spell is forecast while the heads are filling.
| Stage | Main jobs | The risk to manage |
|---|---|---|
| Late winter | Sow indoors, keep above 50F (10C), maximum light | Cold-induced bolting and leggy seedlings |
| Early spring | Prepare and firm the bed, lime if needed | Loose ground that lets plants rock |
| Around the last frost | Harden off, plant out, collar and net | Root fly, pigeons, a late cold snap |
| Three to four weeks after planting | Nitrogen top dressing, earth up, mulch | Growth stalling before the head forms |
| Head forming | Steady water, check the crown for aphids | An early warm spell opening the head |
| After cutting | Liquid feed, pick side shoots every three days | Shoots flowering before you get to them |
Stagger the sowings rather than the plants
Broccoli of one type planted on one day will nearly all be ready within a week to ten days of each other, and a row of six heads at once is more than most households want. Sow small batches two to three weeks apart, or grow two types with different days to maturity, and you spread the cut across a month or more.
Closer spacing works in the same direction and is worth knowing. At 12 inches (30 cm) the heads come smaller and more evenly, which suits a single big cut for freezing. At 18 inches (45 cm) the crop comes over a longer window and gives far more side shoots afterwards. Decide which you want before you plant, because the spacing cannot be changed later.
- Sow six plants every fortnight Three sowings of six spread the harvest over six weeks. It is the simplest way to avoid a glut without needing more ground.
- Mix early and late types Two types with 25 days between their maturity figures, planted the same day, gives you two harvests from one planting session.
- Plan the beds three years ahead Brassicas need a three year gap in the same ground. Sketch the rotation before you sow so you are not forced back onto last year's bed.
One season of notes is worth more than any calendar
Published days to maturity are an average from somewhere that is not your garden. The only figures that will actually be right are your own, and they take one season to collect. Write down the sowing date, the transplant date, the date you first saw the head, the date you cut it, and the date you finally pulled the plant.
Add a note on where each batch sat in the plot and what the weather did during head formation. A single season of that turns next year's plan from guesswork into arithmetic: you count backwards from your cool window using your own numbers, and the sowing date falls out of it.
Also record which bed each brassica crop occupied and whether you found any clubroot on the roots when you pulled the plants. That map is the only reliable basis for a rotation, and it is impossible to reconstruct from memory two years later.