Gilroy gardeners can grow broccoli in spring and fall. Those densely packed heads of unopened flower buds are excellent in salads and casseroles.
But sometimes they don’t grow the way you expect them to. Instead of developing a tightly packed head of green florets, your broccoli heads look a little loose. Then, the florets turn yellow, dry up, and turn brown. This die-off of unopened flowers is called brown bud, or brown bead.
Brown bead is not what causes the black and brown spots on a broccoli that has been kept too long. Those spots are signs of fungal disease. Brown bud is not a disease at all. Instead, it is a physiological disorder. Physiological disorders are those caused by growing conditions.
As a farmer, brown bud can make a crop unsellable, devastating a family’s financial situation. The situation isn’t nearly so dire for home gardeners.
The remaining green portion of the broccoli is perfectly edible, but brown bud does mean a smaller, less desirable crop, and there are ways you can reduce the chance of brown bud occurring in your broccoli patch. Unlike your standard grocery store variety of broccoli, with its tightly packed head of unopened flower buds, heads affected with brown bud have a loose arrangement.
The unopened florets at the center of the head turn yellow (chlorotic), and then brown. This browning can spread across the head. These dead florets break off, providing easy access for bacterial diseases and rotting.
This poorly understood condition most frequently occurs when temperatures are higher than normal for this cool weather crop, especially when clay soil is present.
Brown bud is more likely to occur when there is not enough nitrogen in the soil, and during periods of low relative humidity. Some people believe that insufficient calcium is a contributing factor in the development of brown bud, but research does not support those claims. In fact, in some cases, excessive calcium has been found in broccoli exhibiting brown bud.
If brown bud has been a problem for you in the past, try starting broccoli plants at a time when cooler, wetter weather is expected. Also, be sure to provide plenty of nitrogen.
Fast growing heads are far less likely to develop brown bud. Regular irrigation also helps prevent this disorder. Some cultivars, such as “Skiff,” are more likely to develop brown bud. While others, such as “Coaster” and “Shotgun” are less likely.
To avoid brown bud in your garden-variety broccoli, plant them at the right time, and feed those heads plenty of water and nitrogen.
Kate Russell is a UCCE Master Gardener in Santa Clara County. For more information, visit mgsantaclara.ucanr.edu or call (408) 282-3105 between 9:30 a.m. and 12:30 p.m., Monday through Friday.