|
You’ve probably seen it in your garden. Instead of developing a tightly packed head of green florets, your broccoli looks a little loose and floppy. Then, the florets turn brown. This die-off of unopened flowers is called brown bud, or brown bead.  Brown bud symptoms on broccoli (UCANR) As a farmer, brown bud can make a crop unsellable, devastating your family’s financial situation. As a home gardener, the situation isn’t nearly so dire. Now, we are not talking about the tiny black and brown spots that occur on a broccoli that has been kept too long. That’s usually a fungal disease. You can cut those spots out and eat the rest, but that particular broccoli is probably past its prime.] Brown bud is not a disease. Instead, it is a physiological disorder. Symptoms of brown bud 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.  Broccoli head with poor bud growth (NC State Extension) Causes of brown bud 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.  Close-up view of brown bud on broccoli (NC State Extension) Controlling brown bud
If brown bud has been a problem for you in the past, try starting your broccoli at a time when cooler, wetter weather is expected. Also, be sure to provide plenty of nitrogen, since fast growing heads are less likely to develop brown bud. Regular irrigation can also help 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, feed those heads plenty of water and nitrogen!
2 Comments
Broccoli is the flowerhead of a member of the cabbage family. As a brassica, broccoli is cousin to kale, collard greens, rutabagas, watercress, Brussels sprouts, Romanesco broccoli, and cauliflower. Native to the northern Mediterranean region, modern broccoli is the result of centuries of careful breeding that started in the 6th century BC. Broccoli (Brassica oleracea) has been dreaded by children for decades. This is often due to overcooking and freezing. “Eat your trees!” Mothers have cajoled for generations. The truth is, broccoli contains bitter compounds and some people are more sensitive to them than others. There is no sense fighting over genetics. What you can do, for those family members on the broccoli fence, is to offer fresh, tender broccoli shoots, steam broccoli lightly, and there is always the cheddar cheese trick. [Cheese makes everything taste better, right?]  Mature broccoli plants (UCANR) How to grow broccoli Broccoli is a slow grower. It can take 3 months or more, from seed to harvest. In the Bay Area, broccoli can be started from seed twice a year. For a summer harvest, plant in February, March, and April. For a late winter, early spring harvest, you can plant broccoli in August and September. Some years, you can plant as late as October. Broccoli loves cold temperatures and will bolt in hot weather. Also, heat stress can cause bitterness. Broccoli prefers full sun, but your spring crop can be grown in partial shade, to avoid heat stress, but it will benefit from strong morning sun. Broccoli prefers slightly acidic soil, so your plants will thank you if you perform a little acidification before planting. Seeds should be planted 1/2 inch deep. It is best to start plants in small containers and then transplanting when they have three or four true leaves. Plants can be placed in the ground slightly deeper than the soil level when transplanting. These plants get large, so be sure to provide plenty of growing room. They usually need a 2-foot square space, or more, per plant. Broccoli roots are shallow, so avoid digging around plants. To reduce weeds, mulch heavily. Broccoli needs a lot of water, so irrigate consistently, without getting the heads wet. Broccoli varieties There are three basic types of broccoli. The common grocery store variety is Calabrese broccoli. Sprouting broccoli has many small heads on thin stalks. Purple broccoli looks more like its cousin, cauliflower, with an occasional purple tint to flower buds. Not exactly a true broccoli, broccolini is a cross between standard broccoli and Chinese kale, or gai lan.
According to Santa Clara County Master Gardeners, the following varieties of broccoli perform best in our area:
Broccoli pests and diseases Downy mildews, bacterial leafspot, clubroot, damping off, powdery mildew, phytophthora root rot, and ringspot are common diseases of broccoli plants. Most of these are caused by poor irrigation practices. As for pests, well, we’re looking at all the usual suspects: aphids, whiteflies, bagrada bugs, crickets, earwigs, armyworms, leafminers, slugs and snails, thrips, and wireworms. You will also have to watch for cabbage loopers, cabbage maggots, cabbage aphids, and imported cabbageworms. Bacillus thuringiensis (Bt) sprays can help protect against some of theses. Imported cabbageworms will probably cause the most damage. The larva of an erratically flying white butterfly match the color of leaves and often are not seen until significant damage occurs. Row covers can protect against this particular pest. Since the moths fly, they can always come back to lay more eggs. Personally, I have trained my dogs to chase them away. Once in a while, they actually catch one! Braconid wasps will also help fight off some of these pests, so avoid using broad spectrum pesticides. Environmental conditions can also interfere with a successful broccoli crop. Early stress can cause plants to flower too soon, creating tiny heads. This is called buttoning. Too much heat can cause brown bud - it’s not pretty. Heat (and insufficient boron) can also cause hollow stem. Too much nitrogen in the soil can cause broccoli plants to produce lots of (edible) leaves, but no flowers. [Have I mentioned getting your soil tested?] Harvesting broccoli As flower heads develop, use a sharp knife to cut the stem an inch or two below the head. Delicious fresh, broccoli can be stored in the refrigerator for a short time, or frozen for longer storage. Broccoli is especially susceptible to the ripening effects of ethylene gas, so keep your broccoli away from foods such as apples and bananas. After you have harvested your broccoli, cut plants off at ground level and chop up the remainder, spreading it out over any areas in the garden prone to Verticillium wilt. There are chemicals in broccoli that harm the fungi. Young broccoli sprouts, cauliflower, and mustard greens all contain a chemical called glucoraphanin, which is converted into substances that fight infection, arthritis, and cancer. They can also ‘retune’ metabolism. So, eat your trees! And start planting! Erratically flying white butterflies that look more like moths and favor members of the cabbage family are insidious garden pests. If that weren't bad enough, chemicals found in their favorite foods make them distasteful to birds.  Adult imported cabbageworm (UCANR) The first sign of cabbageworm infestation is random, round holes in the leaves of cabbage, kale, cauliflower, broccoli and other members of the Cruciferae or cabbage family. You may also notice greenish brown fecal pellets littering leaf surfaces. Cabbageworm description Cabbageworms start out as tiny yellow, green, or white, rocket-shaped eggs that are laid singly on the undersides of leaves. If you have a hand lens, you can see distinct ridges on the eggs. Whether you can see that well or not, do your plants a favor and wipe the eggs off whenever you see them.  Imported cabbageworm eggs on the underside of a leaf (USU) Cabbageworm butterflies tend to be white or off-white with one to four black spots on the wings. Larvae are green and fuzzy and can grow to one inch long. Larvae often have a faint yellow stripe on the back and broken yellow lines along the sides. Pupae are a mottled brownish grey.  Imported cabbageworm larva (UCANR) Cabbageworm species There are actually several different white butterflies that lay eggs on plants in the cabbage family. Collectively, they are called ‘cabbage whites’. Native species of cabbage whites include:
The imported cabbageworm, Pieris rapae, has largely replaced these native cabbage butterflies and will be the subject of the remainder of this post.
Damage caused by imported cabbageworm As soon as the eggs hatch, fuzzy green caterpillars start feeding, and feed they do! They start by eating their own eggshell and then they chew round holes in leaves at an alarming rate. Healthy plants can look tattered in only a few days. Leaving trails of brown fecal pellets on leaf surfaces, larvae may also burrow into cauliflower and broccoli heads, making them inedible.  Cabbageworm damage (UCANR) Since cabbageworms are active year round in California, the damage they cause can be extensive. A single adult cabbageworm can fly over 7 miles in a single day, so you really need to be on the alert.
How to control imported cabbageworms Unlike many other invasive pests, imported cabbageworms actually have some enemies already. Tachinid flies and a handful of parasites feed regularly on cabbageworm eggs and larvae. Speaking from experience, I can tell you that those natural controls will not be enough once cabbageworms have found your crops. You can spray Bacillus thuringiensis (Bt) or spinosad for a measure of organically acceptable control. Handpicking is really your best control. And get rid of any nearby weeds from the cabbage family. Adult cabbageworm butterflies feed on nectar from flowers, preferring blooms of purple, blue, and yellow. Personally, in addition to regularly monitoring plants for the presence of cabbageworms, I have trained my dog to chase cabbage butterflies out of my yard. It helps, and it’s pretty fun to watch. |
Welcome!You can grow a surprising amount of food in your own yard. Ask me how! 
Index
All
Archives
October 2019
|
RSS Feed