Generally, seeds are planted indoors between March and June. Until April, sow two seeds per module in modular trays in a greenhouse or inside; beginning in April, sow outdoors. After germination, remove the smaller or weaker seedlings, leaving just one per module.
- Apply a liquid general-purpose feed weekly.
- When the young plants grow 10–15cm (4–6in) tall with a healthy rootball, put them in sun or light shade in fertile soil outside.
- Add three handfuls per square metre/yard of a high potassium general fertiliser, such as Vitax Q4, to prepare the soil.
- Alternatively, apply half as much fertilizer if well-rotted manure or garden compost has been dug in.
Plants should be spaced 30cm (1ft) apart, with 45cm (18in) separating rows. Closer spacing will decrease the quantity of side shoots, resulting in a lesser harvest.
How widely apart should broccoli seeds be planted?
Plant Thinning – When direct sowing broccoli, the seeds are spaced a few inches apart. This is due to the possibility that not all of your broccoli seeds will germinate and generate plants. Even if just a few of the seeds sprout, it is likely that the seedlings will be too close together for the broccoli plants to flourish and grow to maturity.
Where to Sow – Broccoli thrives in full sun and soil that is slightly acidic — with a pH between 6.0 and 6.8 — fertile, well-drained, continuously wet, and abundant in organic matter. The correct pH and organic matter contribute to the availability of minerals, especially critical micronutrients such as boron.
A boron deficit can cause broccoli stems to become hollow, but too much boron is hazardous to plants, so is necessary. There are special spacing requirements for autumn broccoli. If you are gardening in a bed, place the plants 15 to 18 inches apart; if you are gardening in rows, space the transplants 18 to 24 inches apart inside the row and 24 to 36 inches apart between rows.
Set transplants somewhat deeper in the soil than they were in the container.
What is the optimal technique to cultivate broccoli?
Grow – Broccoli grows best on soil that is healthy, well-drained, and moisture-retentive, and in full sun or moderate shade. To eliminate cabbage root flies, cover seed beds and newly transplanted indoor-raised plants with fleece. In May, when the risk of harm is minimized, it can be removed.
- In dry conditions, broccoli should be watered every 10 to 14 days.
- Add a strong nitrogen fertiliser, such as sulphate of ammonia, at a rate of 35g (1oz) per square metre/yard when plants are approximately 20cm (8in) tall.
- Birds can be a problem, so net the plants as the heads begin to develop.
- Some cultivars are more resistant to this propensity than others.
Better heads are produced in cooler summers, as high temperatures promote plants to go to seed early (see Recommended Varieties below).