Broccoli is a cold-weather crop.
"Bolting" is when broccoli sends up seed stalks. The process is also known as flowering, as in "the broccoli has gone to flower" or "gone to seed." Once the broccoli bolts it becomes bitter and inedible, so there are good reasons to do what you can to prevent it.
Cold-Weather Vegetables
Broccoli is a cold-weather vegetable, which means that it is planted two to three weeks before the last predicted frost date for the area. Cold-weather crops such as broccoli must mature while the weather is still cool; hot weather and warm soil do not favor broccoli development and will quickly cause the plant to bolt.
Temperature and Bolting
According to Chris Smith of the "Seattle Post-Intelligencer," fluctuating cool and warm temperatures are one of the most common causes of broccoli bolting. This type of weather pattern tricks the young starts into thinking they've gone through winter and the arrival of warm weather causes them to send up their seed stalks too early. Floating row covers, which are used to prevent maggot infestations and to warm the soil, can also cause bolting when they are left on the ground too long and the soil becomes too warm. Smith recommends removing floating row covers when the broccoli stems are 1 1/2 inches in diameter and the plants themselves are about knee-high.
Transplants
In their eagerness for a lush garden and fresh, garden-grown produce after a long winter of supermarket fare, some gardeners may purchase larger transplants in the hope that this will result in more broccoli at a faster rate, but this is not the case. Those larger transplants are more likely to bolt than transplants that are about 7 to 8 weeks old, according to Smith. How can you tell the age of your transplants? Purchase them from the person or nursery that grew them or grow your own.
Prevent Bolting
Mulch is one of the best ways to prevent broccoli from bolting, because it keeps the soil temperature cool even when the air temperature is warm. There are several different forms of mulch, but straw, bark mulch and leaf mulch are some of the best. One bale of straw is inexpensive and goes a long way in the garden. Put down 2 to 3 inches of mulch to keep soil moist and cool for longer periods of time. Also, you might consider purchasing bolt-resistant varieties of broccoli if temperatures where you live are truly unpredictable.
Tags: Broccoli cold-weather, larger transplants, seed stalks, warm soil, when broccoli
