As it's a brassica, broccoli is susceptible to several pests and diseases that affect the cabbage family, including clubroot and cabbage root fly. It is best grown under fine-mesh netting to protect it from cabbage caterpillars and pigeons. Cabbage whitefly and aphids may sometimes be problematic.
Broccoli's optimum growing conditions include a location with well-drained, fertile soil with a pH of 6.0 to 6.5 and at least six hours of sun. Soil test your location several weeks prior to your planting date to adjust and apply amendments accordingly. Avoid soils that are sandy or hold too much moisture.
Broccoli is one of my favourite vegetables to grow and easier to grow than cauliflower or Brussels sprouts. Many gardeners don't bother with it because it occupies a large space and takes so long to grow, but once you know how to grow broccoli, it really isn't a difficult crop.
Feed your broccoli.
Another cause of an absence of heads, or even slow growth in the plants, could be lack of adequate nutrition. Broccoli is very heavy feeding and thrives on nitrogen.
Broccoli is a cole crop which means they prefer cooler temps. If temperatures are too warm, they will not create heads.
For the fall crop, start seeds indoors or out, in early to late July. Gardeners in northeastern Minnesota can grow broccoli all summer long. After you harvest the main head, smaller side shoots will grow for another harvest. Broccoli will continue to grow after the first light frosts in the fall.
Broccoli, another vegetable in the brassica family, isn't a good choice for planting alongside tomatoes. That's because tomatoes are notoriously hungry for nutrients, and broccoli will compete for the same selection of nutrients in the soil.
Ensure that the plants are receiving adequate water and nutrients. Broccoli doesn't usually require additional fertilizer, but if the plants look sickly, hit them with some nitrogen such as fish emulsion. Time your plantings properly since extreme heat or cold has a bearing on whether or not the plant heads.
Temperatures above 35 degrees Celsius (95 degrees Fahrenheit) for more than four days during that period causes uneven bud development at the bud initiation stage, resulting in heads that were uneven and poorly shaped. Other references suggest that temperatures above 85 degrees can cause heat injury.
Broccoli requires proper irrigation to achieve optimum growth. Water plants daily for the first week to get the crop established. Continue to irrigate broccoli every four to five days, as needed, to keep the plants healthy. Broccoli is a fairly heavy feeder and will require additional nutrients.
Broccoli likes steady moisture to grow fast and produce good heads, so water regularly, applying 1 to 1.5 inches of water per week if rain doesn't cover it. You can measure the amount of water with a rain gauge left in the garden.
A head of broccoli is considered the main stem and branch. Each plant produces just one head. Once the large central head is harvested, florets continue to emerge from leafstalks. Much smaller, these also are edible.
The soil should be loose, just moist, and about neutral pH. I use a 5-10-10 N-P-K fertilizer, broccoli requiring more phosphorus and potassium than nitrogen.
Broccoli craves the sun. Yet, like a pale-skinned beachgoer, it can't handle the full brunt of a midday sunbath. Six hours of direct sunlight strikes the balance between a healthy glow and a sunburnt flop. In scorching climates, afternoon shade is broccoli's best friend to prevent premature bolting.
The best way to prevent it from bolting is to keep the roots cool and moist. Use a deep layer of organic mulch, such as grass clippings, leaves or straw. These mulches will insulate the ground, keep moisture in the soil and block out direct sunlight.
In most broccoli varieties, numerous side shoots form as well. These smaller heads continue to mature after the central head is harvested, and are the best way to have a second - and sometimes a third - crop of broccoli from a single plant. Follow the same guidelines for when to harvest.
Broccoli needs plenty of nutrients, so be generous with compost and a balanced organic fertilizer when preparing planting space. Big broccoli plants rock in the wind, but not when they are firmly anchored in their favorite soil type, which is dense, clay-based loam with a near-neutral pH.
As well, weather too chilly in spring–just three or four days below 50°F–will cause broccoli to form button-like flower heads that will never develop. Do not plant out broccoli until the weather is settled. For a fall crop, sow broccoli in the garden 10 to 12 weeks before the average first frost in fall.
However, because they are both heavy feeders, require a lot of moisture and light, and need adequate space around them to promote healthy air circulation, they may compete. In light of this, if you want to grow cucumbers and tomatoes together, it is best to plant them 45 – 60 cm apart and in separate soil if possible.