Growing Broccoli in a Short Season: Transplants, Pests and Side Shoots

Broccoli loves cool weather, which makes it a great fit for a northern garden. Start it indoors, get it out once the worst frosts are past, keep the bugs off and you will be cutting heads in early summer, with side shoots for weeks after.

The short answer

• Start indoors 5 to 6 weeks before planting out (about the first week of April for a mid-May last frost).
• Plant out when days reach about 10°C and nights stay above −2°C for several nights.
• Space plants 30 to 45 cm apart in rows 60 to 85 cm apart.
• Cover with a row cover right away to stop flea beetles and cabbage moths.
• Cut the main head, then keep harvesting side shoots.

Based on the University of Saskatchewan broccoli guide.

Starting broccoli indoors

• Sow 0.5 cm deep, 2 to 3 seeds per pot, and thin to the strongest.
• Seeds germinate in 5 to 6 days at 24°C.
• Give 14 hours or more of light, and run a fan or brush the tops daily for sturdy stems.
• Feed with a diluted balanced fertilizer once true leaves appear.
• A good transplant is 10 to 15 cm tall, dark green and not root-bound.

Planting out

Harden off for at least 3 days. Plant out once days reach about 10°C and nights stay above −2°C for several nights; in Saskatoon that is usually after mid-May. Cover the whole root plug and loosen the roots gently. Mature broccoli is frost hardy, but young transplants are not, so keep a cover handy for late frosts.

Varieties

North Dakota State University currently recommends Green Magic and Packman for prairie conditions. Many other hybrids did well in USask’s older trials, including Arcadia, Belstar, Diplomat, Eureka, Ironman and Marathon.

Keep the pests off

• Flea beetles chew small holes in young leaves. Cabbage moths lay eggs that become green caterpillars.
• A lightweight row cover installed right after planting, before the insects arrive, is the best non-chemical defence, especially near canola fields.
• Push a cutworm collar (a toilet paper roll or a can with both ends removed) 5 cm into the soil around each transplant.

Water

About 2.5 cm a week. Broccoli survives dry spells but gives much smaller heads.

Harvest

1. Cut the main head when it is firm and dense, before the tiny buds start to open yellow. In cold-climate gardens this is often early to mid-July.
2. Cut just below the head at a slight angle, leaving 12 to 15 cm of stalk with leaves.
3. Side shoots will form along the stalk. They are smaller but tender, and you can pick them several more times.

Broccoli keeps a few weeks in the fridge, ideally near 0°C with high humidity. Blanch and freeze extra.

Keep reading

• Growing kale in a cold climate
• How to start seeds indoors in a cold climate

Frequently Asked Questions

When should I start broccoli seeds indoors?

Five to six weeks before planting out, about the first week of April for a mid-May last frost.

When can broccoli go outside?

When days reach about 10°C and nights stay above −2°C for several nights in a row.

Will broccoli grow back after cutting?

Yes. After you cut the main head, side shoots form along the stalk and can be harvested several more times.

How do I keep worms off broccoli?

Cover plants with a lightweight row cover right after planting, before cabbage moths can lay eggs.

Sources

• University of Saskatchewan Gardenline – Broccoli