I've had many gardeners complain to me that they can't get their broccoli to grow decent heads. In this video, I show how I plant my broccoli to produce large gorgeous heads – including the size of the containers I grow the seedlings in, how deep I put the transplants, how far apart I space them, and how I keep cabbage worms off my plants.
This isn't the only way it can be done, however. It's just what has worked well for me.
I like starting my plants in larger than usual containers (3″ wide by 4″ deep), because it helps to produce large vigorous plants and it keeps the young plants from becoming root bound – which often causes broccoli to fail to form good heads. But I do know other gardeners that grow good broccoli using smaller containers.
Unfortunately, many nursery-grown broccoli transplants are sold in tiny containers in a severely root bound condition. That's one reason why I prefer to grow my own transplants. I can also choose from a wider number of varieties when I purchase seed instead of seedlings.
I space my broccoli 16-18″ apart (40-45 cm). It's often recommended to plant them just one foot (30 cm) apart, and you can definitely harvest good broccoli with that spacing. But I've learned that I can harvest just about as much broccoli per square foot using wider spacing, and with the wider spacing I only need 40% as many plants. However, I grow a variety that has been bred to produce large heads – Arcadia. It is also a very cold hardy variety that can produce a lot of side shoots.
As for the cabbage worms, I usually prefer to use row cover or fine netting to keep the butterflies and moths off of my plants. However, you can choose to spray the plants with BT (Bacillus Thuringiensis), an organic pesticide composed of bacteria that only affects caterpillars. Or you can remove the tiny green caterpillars hiding inside the broccoli heads by hand after harvest – which I've done, but it's extremely tedious and time-consuming when you are processing many heads.
I obtain resin-coated fiberglass rods through 7 Springs Farm in Floyd County, Virginia.