Broccoli Planting Times in Southern Illinois

Spring Planting Dates

• The University of Illinois Extension describes broccoli as a half-hardy vegetable, meaning it can withstand mild to moderate frost. With southern Illinois’ median last spring frost date ranging from April 8 to 22 and broccoli’s ability to be planted two to three weeks before the typical last spring frost date, you could plant anywhere from March 29 through April 17, depending on your area. Alternatively, wait until the soil has reached 65 to 75 degrees Fahrenheit for optimal germination, or at least 50 degrees for slower germination.

Fall Planting Dates

• In southern Illinois, you should have time for a second broccoli crop, if you plant well in advance of the typical first frost, which ranges from Oct. 14 to 21. The far southern part of the state often sees the latest frost date. Recommended planting dates based on information provided by the extension service are July 24 to Aug. 3. The latest planting dates apply to gardeners living the farthest south. Before sowing seeds, remove all plant debris, spade or till the soil to a depth of 6 to 8 inches, and refresh your soil with at least 2 inches of compost. You want to replace the nutrients taken from the soil by previous crops. Broccoli can stay in the ground through mild frosts, but harvest any side shoots before a predicted hard frost.

Setting out Transplants

• If you are anxious to get plants started, yet the ground is still too cold, start broccoli seeds indoors. They can be grown under lights, beginning four to six weeks before the average last spring frost date in your part of the state. On planting day, set the seedlings out in cloudy weather or during the late afternoon to minimize transplant shock. Water them deeply before transplanting, removing the plants from their pots without disturbing the roots. Set the seedlings in the soil at the same level as they were growing. Tuck at least 2 inches of compost around the plants mid-season; broccoli is a heavy feeder. Cultivars recommended by the University of Illinois Extension include “Cruiser,” “Green Comet,” “Green Goliath,” Premium Crop” and “Packman.” All mature in 55 to 60 days. Only “Premium Crop” is resistant to downy mildew.

Diseases

• Broccoli grown in southern Illinois can be plagued by aster yellow. A bacteria transmitted by the six-spotted leaf hopper, aster yellow causes the leaves to turn yellow, stunting growth. Although no disease-resistant cultivars exist, thoroughly cleaning crop debris at the end of the growing season, keeping the area around the plants weed-free and covering the seedlings with a floating row cover to keep insects away lowers the chance of infestation. As with all pests and diseases, rotate crops each year to avoid unwanted insect and bacteria buildup in the soil.