Resolving Brussels sprout and red cabbage garden mysteries

By Kathryn Fontenot

Louisiana fall gardens almost always include cabbage plants. Whether you grow them for nourishment, coleslaw, eggrolls, relish, or salads … or perhaps to throw in St Patrick’s Day Parades, they are generally a staple crop of fall gardens. In general, Louisiana gardeners can grow really, really nice cabbage heads – green ones, that is. 

Bitesize Brussels

Traditional green cabbage varieties such as ’Flat Dutch’, ‘Megaton’, ‘Cheers’, ‘Blue Dynasty’, ‘Emblem’, and others – the list goes on and on – grow well, provided the gardener provides plenty of water and fertilizer. But red or purple cabbages in Louisiana tend to stay small; even excellent gardeners only achieve rock hard heads the size of a baseball. 

Why won’t the red or purple varieties grow well? Is it because you aren’t planting the correct variety? LSU AgCenter recommends ‘Red Vantage’ and ‘Scarlet Queen’; do those mature into large heads? No, not really. Even in LSU AgCenter trials, such as the 2017 fall red cabbage variety trial, the average red cabbage head was 1 pound (edible portion). There were of courses differences in average head size of the trialed varieties. ‘Rio Grande Red’, ‘Red Express’, and ‘Scarlet King’ clearly weighing-in heavier than others. But overall, size was disappointing. 

So if it’s not the variety selection, what is the problem? Many growers claim you must double the rate of fertilizer to grow large red cabbage heads. We packed quite a punch of fertilizer in the 2017 trial and were still unsuccessful. But doubling the rate or fertilizing with a heavy hand might just be the ticket. A normal rate of preplant fertilizer for cabbage plants is 5-6 pounds of 8-24-24 or 13-13-13 per 100 feet of row; for smaller gardens, ½ or just a bit more for a 10-foot row. To achieve really large heads you must fertilize (side dress) again with 4 pounds of calcium nitrate (or fertilizer with 15 percent nitrogen) for every 100-foot row; translated for smaller gardens – ¼ pound of calcium nitrate for every 10 feet of row. Apply this rate as side-dress fertilizer three to four weeks after planting and again two more times in two-week increments. My great garden friend Jimmy Boudreaux recommends a fourth application for red cabbage varieties to help get that size up. The vegetable team at the LSU AgCenter will try again. This time we will conduct our trial using our favorite varieties and look at various fertilizer rates to determine if the current recommendations should be increased. 

Brussels sprouts developing on the stem

While every home gardener wants bragging rights for giant cabbage heads, we definitely do not want to ruin the environment. There are hundreds of research studies being conducted regarding excess phosphorus and potassium entering our waterways. Excess fertilizer runoff from big ag and non-point sources (such as home gardens) have caused algae blooms, dead zones, and much larger problems than small cabbage heads. Even if all of this does not bother you, (But hopefully it definitely does –Ed.) and you still think, “Dead zones … whatever, I want a large cabbage.” Overfertilization causes excessive salt buildup in YOUR garden, which prevents future plantings from yielding. Too much of a good thing can sometimes become a bad thing after a year or two …  or three or four. So before doubling rates, and definitely before we know the results of the abovementioned studies, let’s just apply the fourth side-dress application and see if that bumps the heads up 1-2 pounds. 

Another fall garden mystery or question we hear year after year is, “When will my Brussels sprouts develop heads?” My answer is “Patience is the key to growing Brussels sprouts.” In the U.S., 98 percent of the Brussels sprouts are grown in California and the other 2 percent in New York. These numbers represent commercial production, not hobby, small farms, or home gardens. But anyone can clearly see that Louisiana weather is not the same. Even in ideal Brussels sprout conditions (cool, but not freezing, temperatures), Brussels need anywhere from 120 to 180 days to develop. So patience is of the essence, as is a large garden where you can dedicate almost half a year to the growth of this one plant. 

A nicely developed red cabbage head

But even if you possess the patience of a monk, you still may not develop tight sprouts. So what is going on? Typically the sprouts growing along the stalk of the plant mature from the base upward. To force the plant to focus on bud development rather than overall plant growth, you can “top” the plant. Topping is pinching off the apical meristem or the top portion of the plant. This practice is typically done when the bottom sprouts start to develop and mature. Topping will usually hasten the process of sprout development, along with applying the appropriate amount of fertilizer. A well-fertilized plant will develop heads, whereas a starved plant will not. Typical fertilizer recommendations for Brussels sprouts are the same as the cabbage recommendations listed above (pre-plant and side-dress).  

LSU AgCenter also conducted a Brussels sprout variety trial in the fall of 2017. The best producer in terms of number of buds per plant, larger bud diameter, and total bud weight was ‘Capitola’. ‘Capitola’ seed was sourced from Stokes Seed for this experiment. Not ranking in the top producers, but yielding small, tight, nice-tasting buds – and maybe even my favorite of the trial – was ‘Bitesize’. ‘Bitesize’ seed was sourced from Park Seed for this trial. The sprouts were perfect, no blemishes even under not one but two snows in the field! Many of the varieties looked damaged after the two snow incidents, but when the outer wrapper leaf was removed, a beautiful sprout was reveled; it just took a lot of extra labor. But that extra labor was not necessary for ‘Bitesize’. 

A nicely developed red cabbage head

What was most surprising about growing Brussels sprouts in Louisiana wasn’t the field performance, but poor seed germination. If you can purchase transplants go for it. If not, you’ll need five to six weeks to produce a transplant from seed. In our 2017 trial we started with 21 varieties of Brussels sprouts but because of poor germination (after starting seed on three separate occasions) went to the field with 12 varieties. So if you plan on growing your own from seed, let me save you a little money and say that our best germinations came from ‘Capitola’, ‘Bitesize’, ‘Franklin’, ‘Cobus’, ‘Gustus’, ‘Diablo’, ‘Jade Cross’, and ‘Hestia’. All of which had 85 percent or better germination. This is very important since we typically plant Brussels sprout transplants September through early November, therefore starting the seed when the temperatures can be very warm.  

So grow green cabbage to feel successful; grow red cabbage to challenge yourself; and grow Brussels sprout to learn the art of finding calmness or inner peace and patience in the garden.

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