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Jessica Walliser

Broccoli's best days are early spring

Jessica Walliser
| Saturday, March 5, 2016, 8:00 p.m.
If planted early enough, broccoli can produce plentiful, delicious florets for several weeks.
Jessica Walliser
If planted early enough, broccoli can produce plentiful, delicious florets for several weeks.

Broccoli is one of the easiest vegetables to grow in a home garden. If it's planted at the right time and cared for properly, a broccoli plant can produce delicious, edible florets for many weeks.

Broccoli is a cool-season crop. It might be hard to believe, but it is the same species of plant as cauliflower, cabbage, kale, brussels sprouts, collard greens and kohlrabi. These vegetable varieties were all created from the same species of plant (Brassica oleracea) by selectively breeding for certain traits over many generations. Collectively, they are known as the cole crops.

Because broccoli and other cole crops prefer to grow in cooler weather, your greatest chances of a successful broccoli harvest involve an early planting time. If you wait until the weather warms to plant broccoli, the plants will bolt, or go to flower, very early, often before you can harvest a decent-sized head of broccoli.

In Western Pennsylvania and many other parts of the country, broccoli seeds can be started indoors, under grow lights, anytime between early February and mid March. If you don't want to start your own seeds, most local nurseries will have broccoli transplants available within the next few weeks.

Young broccoli plants should be planted out into the garden sometime between mid March and early May. Before planting, work a few inches of compost into the soil. Avoid using manures or granular fertilizers rich in nitrogen in the planting area, because the excessive nitrogen present in them will likely result in big leaves and very small heads.

The optimum soil pH for broccoli, and most other vegetable crops, is 6.5. The pH of the soil is important because it determines the availability of almost all nutrients, including phosphorous, which is essential for good broccoli development. Ideally, you should take a soil test every three to four years and adjust the pH as necessary. You can get soil testing kits for $12 from the Penn State Extension Service (412-263-1000 or extension.psu.edu/allegheny/news/spotlight/penn-state-analytical-laboratories-test-your-soil-and-water).

Space broccoli plants 18 to 24 inches apart to give them plenty of room to grow. If planting in rows, space the rows 36 inches apart.

All cole crops are very cold-hardy and do not need to be protected from frosts, but if you want to shield your young broccoli plants from the cold nighttime temperatures of early spring, you can cover each transplant with a bottomless milk jug with the cap removed. This cloche will stabilize the sometimes-extreme weather fluctuations of spring. But, the cloches should be removed on very warm days to keep the plants from prematurely bolting. And they should be permanently removed when the plants outgrow them.

To prevent cabbage worms from ravaging your crop, cover the broccoli plants with a layer of floating row cover immediately after planting (or after the cloches are removed). This lightweight fabric rests on the top of plants and prevents the adult cabbage moths from accessing the plants and laying their eggs. You can purchase it at most local nurseries or online. Because broccoli does not need to be pollinated to produce a crop, the row covers should be left in place until the day of harvest.

Broccoli heads are ready to harvest when the buds on the outermost portion of the head begin to swell. Use a sharp knife to slice off the heads, but leave the plants in place as they will produce many secondary florets after the main heads have been harvested. As long as these secondary florets are regularly harvested, the plant will continue to produce them.

Once hot summer weather arrives, production will slow, the florets will quickly go to flower, and their flavor will turn bitter. At that time, you can pull out the plants and replace them with a summer crop of green beans, basil or another warm-season vegetable, or allow the broccoli plants to go into flower.

The flowers of all cole crops are attractive to pollinators and other beneficial insects, and will provide these garden helpers with essential pollen and nectar until the end of the gardening season.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is jessicawalliser.com.

Send your gardening or landscaping questions to tribliving@tribweb.com or The Good Earth, 503 Martindale St., 3rd Floor, D.L. Clark Building, Pittsburgh, PA 15212.

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