Perhaps a few people get lucky on their first try, but most gardeners spend several seasons learning how to grow broccoli (calabrese). This is because garden broccoli has more precise cultural requirements compared to other vegetables. On every level – timing, soil fertility, spacing, and pest management – broccoli’s rather exact needs must be met. But once you figure out broccoli’s secret formula for success, you can look forward to bountiful yields of this popular and nutritious vegetable.
Getting spring and fall planting times right is the first challenge. The GrowVeg Garden Planner will generate suggested planting dates for your area, but because broccoli is such a difficult child, you should watch each broccoli planting closely, keep records, and talk with your neighbours in attempt to discover the best dates for you. In my climate, for example, I have learned to start my spring crop indoors around March 1, and to start my fall crop around June 15 (this I learned from a more experienced neighbour). Equally important for Garden Planner purposes is the end date of my spring planting, which for me is July 7. Your exact dates will vary, but this is the kind of invaluable data you will need to grow broccoli like a pro. Nail your dates, add them as notes to your Plant List and the Garden Planner will never let you forget them!
We also suggest sticking with 18-inch (45 cm) spacing, unless you are growing a miniature variety intended to be grown in close quarters. Although small seedlings may look lost when set out this far apart, they will quickly fill in the space. Crowding plants often leads to tiny heads and no production of sideshoots, or ratoons.
Of Birds and Broccoli
Most people don’t associate broccoli with birds, but studies from Egypt and the USA have shown poultry manure to be a superior fertiliser for organically grown broccoli. I have had excellent results using a processed turkey manure fertiliser to grow the Belstar variety, a hybrid that is widely available as organic seed
I spoil my garden broccoli with fertile, well drained soil with a maximum safe dose of turkey manure fertiliser worked in two weeks before planting, but I have use little or no mulch for my spring crop to reduce problems with slugs. This has worked out well though it means more weeding for me. With or without mulch, controlling weeds is essential to growing bumper crops of broccoli.
I think that robins and other bug-eating birds help reduce problems with the velvety green caterpillars, larvae of the cabbage white butterfly. But they can’t do the job alone. I protect plants with row covers until they get too big, and then use spinosad, a biological pesticide, if I see evidence of caterpillar feeding or the garden seems mobbed by cabbage white butterflies. It is incredibly effective.
Off With Their Heads
When little heads begin to form in the plants’ centres, I make sure my broccoli never runs short of water. On very sunny days, I use a wooden clothespin to fasten three or so leaves together over each ripening head, because too much sun can sharpen broccoli’s flavour. I cut the main head when the florets are still tight, cutting high on the stem so side shoots will have ample room to grow. The side shoots are usually ready two weeks after the main head is harvested.
Learning how to grow broccoli usually involves some trial and error, as is shown in Mother Earth News’ Survey of Most Productive Garden Crops. On a scale of 1 (low) to 4 (high), gardeners gave broccoli a 2.4 in terms of ease of culture, but rated it at 3.4 when it came to how much they wanted more garden broccoli in the kitchen. Behind those numbers, the truth is that broccoli is a crop that needs to be attentively courted before it will become your sweetheart.
[UK readers please note that green broccoli is often referred to as calabrese in seed catalogues and our UK Garden Planner to distinguish it from purple sprouting broccoli]