How to Grow Broccoli in Wisconsin (Zones 3-5)


Broccoli is one of the easiest vegetables to grow in Wisconsin!

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Broccoli is not only my favorite vegetable to eat, but it is one of my favorites to grow in my garden: it’s pretty easy to grow, can be planted in either the Spring or late-Summer, is healthy, and tastes delicious! With just a few tips on how to grow broccoli in Wisconsin, you can be enjoying your own this year!

How to Grow Broccoli in Your Garden in Wisconsin (Growing Zones 3-5)


If you live in Wisconsin or any zone 3-5, Broccoli is one of the easiest vegetables to grow if you start on time. A member of the cabbage family, broccoli can be harvested several times during the summer growing season and in the fall growing season. Timing and temperature are critical for growing broccoli in Wisconsin. The ideal growing temperature range is 65 to 80° F.

Broccoli one of those cool weather crops that do not like hot and humid weather. Broccoli will bolt (go to seed) if they get too warm, so that is why most people grow broccoli as a fall crop rather than a summer crop. Start transplants indoors if you don’t want to buy seedlings and transplant them into your garden. Broccoli does not transplant easily, and it’s best to start this vegetable from seeds.

Starting Broccoli From Seeds

Sow seeds indoors, one to two weeks before the last frost date. Keep soil temperature around 70º to 75ºF, and plants will germinate in 5-7 days. Harden off and transplant outside after all danger of frost has passed. Space broccoli 15-18 inches for spring planting and 8-10 inches apart for fall plantings. Fall plantings will need protection from snails or slugs. I like to start my seeds indoors at the beginning of March for my summer garden. And I start my seeds at the end of June or early July for my fall garden.

  • What Broccoli Seeds Should You Buy? Savoy variety is the most desirable in taste and texture even though it is not as hardy as Floribunda and compact varieties. In Wisconsin, Savoys still yield into December when grown late. Unfortunately, like cauliflower, broccoli is subject to several diseases, including black rot, blackleg, and clubroot which attack the roots. However, tolerant varieties provide reliable harvests even under adverse conditions.

After seedlings emerge, you will need to keep the soil evenly moist. Tiny broccoli plants usually appear in about 10 days after sowing; transplanting can be done when the plants are 2 to 3 inches tall. Harden off before transplanting outdoors by gradually exposing plants to outdoor conditions over a 7-10 day period.

Transplanting Your Seedlings to Your Garden

Broccoli needs cool weather, full sun, water, and rich soil. Plant your broccoli to get at least 6 hours of daily sunlight in fertile, well-draining, moist soil with plenty of organic matter.

Space seedlings plants 8 to 12 inches apart in rows 18 to 24 inches apart; set plants 2 to 2-1/2 inches deep with the center of the crown just above the ground. Mulch and keep the soil moist by watering deeply two to three times per week.

For optimum growth, it’s essential to use a combination of premium-quality soil and plant food to support your plants. You can improve your soil by mixing compost into the top few inches of native soil. You’ll also want to feed regularly with a continuous-release fertilizer like Miracle-Gro Organics® Edibles Plant Nutrition Granules, or I like to use Fish Emulsion fertilizer. Fish emulsion is appropriate for feeding leafy green vegetables (such as Brocolli, Spinach, Kale) due to its high nitrogen content.

Caring for Your Broccoli Garden

Broccoli needs 1 inch or more of water per week if temperatures are above 85ºF degrees. The amount of water needed will need to be increased if rainfall is below average. Caleb set up multiple sprinklers on a timer for me so that my garden would be properly watered.

Broccoli will tolerate light frosts and freezes but is best planted after the danger of hard frost has passed; however, a cold spell will be tolerated if the temperature remains above 30ºF. Fall broccoli growth is best with night temperatures between 50º and 60ºF degrees and day temperatures between 70º and 80ºF degrees; however, plants may need protection from late-season freezes.

The best way to avoid pest problems is to keep your plants healthy and your garden clean. The main insect pests include cabbage loopers and imported cabbage worms, cabbage root maggots, aphids, and flea beetles. I like to use Bonide Caterpillar and Worm Killer.

Harvesting Your Broccoli

For the best results, when you see a flower head beginning to form in the center of the plant, check its growth every day. Broccoli is ready to harvest when the head is large, and the buds are very tightly close together. Harvest broccoli when the head is firm but before any yellow shoots or flowers appear. Then, take a pair of garden shears or scissors and cut them at the base of the broccoli head.

Careful handling will increase the storage time for fall-grown broccoli. Tie harvested plants into bunches and place them in a shaded, well-ventilated area with good air circulation until ready to process or store.

Don’t be disappointed if your broccoli head is smaller than those at your local grocery store, especially in locations where the Spring temperatures heat up fast. Also, broccoli heads are often better in Fall gardens than in Spring because sometimes temperatures rise too fast, and the broccoli will bolt. No worries, though! You can start seeds and plant in late summer!

Storing Your Broccoli

Broccoli can be stored in the refrigerator for about two weeks without washing. After harvest, cut the head from its stem and wrap it in moist paper towels. Store in a plastic bag with a ripe apple for three to four days; discard the apple if it begins to rot.

Broccoli cooked ahead of time may be frozen with minimal loss of quality and flavor. However, like most vegetables, broccoli’s vitamins will deteriorate when it is frozen and then reheated. Therefore, frozen broccoli should be stored in a freezer for up to six months. Broccoli is an excellent vitamin A, vitamin C, and potassium; it also provides vitamin B1, calcium, phosphorus, and iron.


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