Broccoli (Brassica oleracea) is among the most challenging -- yet most rewarding -- annual vegetables to grow. The advantages, of course, include introducing your family to a vitamin and fiber-rich food they'll be more likely to eat after helping to nurture it. Possible pitfalls, unfortunately, center around broccoli's slightly fussy nature. Don't be surprised if your first crops fail to resemble the uniform, tight heads you find in the grocery store. Potential culprits are weather and soil issues, as well as what variety of broccoli you've chosen to grow.
Mistakes made any time from planting to harvesting can lead to loose broccoli heads. Whether you grow your own plants from seed or buy them as seedlings, young broccoli that isn't transplanted soon enough will "button," or develop small curd-like heads rather than one large, tight head. Choose only your leafiest, greenest seedlings for transplanting, and set them out as soon as they have four to six leaves. It's also important to handle transplants gently because damage to the seedlings can cause a condition known as "blindness," which shows up as tough leaves and misshapen heads. Failure to give broccoli plants adequate water, especially when temperatures rise, can cause heads to loosen.
Planting broccoli too late in the spring, or too early in late summer, can cause "ricing," or flower heads forming early, creating a fuzzy, looser head. The longer this cool-weather crop is exposed to hot summer days, the less likely it is to form a perfect tight head. But even with the best of planning, you won't always be able to control unexpectedly hot weather. Shade cloth can be set over your broccoli bed when unseasonably high temperatures are predicted. It also helps not to overfeed broccoli plants, because high heat combined with high nitrogen puts the plants at increased risk of ricing.
Before planting, conduct a soil test on your garden with a home kit or through a professional service. Buttoning can be the sign of nitrogen deficiency, which is especially an issue during periods of heavy rain or if you soil is on the sandy side. Working a 2-inch layer of compost into the soil before planting, and setting another 1 inch of compost around plants when they are about six weeks old helps mitigate these conditions. Extra nitrogen can also be given to the plants in the form of liquid fish emulsion if you suspect a deficiency. Unless package directions indicate otherwise, for every 100 square feet of your broccoli bed dilute about 1 tablespoon of the concentrate with 1 gallon of water. Use a watering can or garden spray to water the plants and the soil. In some cases, a boron deficit can lead to loose or misshapen heads. To correct a suspected boron deficiency, mix 1 tablespoon household borax with 1 gallon of water for every 100 square feet of broccoli crops, and then water the plants with this solution.
In some cases, what looks like an imperfect broccoli to you may be simply a variety that you aren't used to. Some broccoli types form several individual heads rather than one large, tight head. This category is known as floret, sprouting or Italian broccoli. Cultivars include "Early Purple Sprouting." In addition to the unexpected surprise of an unfamiliar broccoli type, you may be unaware of broccoli's ability to form small heads along the sides of the plant after the main head has been removed. This is another case of a broccoli plant functioning in a healthy way, although at first glance the older plants can look like a series of messy, loose heads.