Becky Weeks - Dec 4, 2023
Secrets to Growing Collosal Cabbages
The sun dawned bright and warm one Saturday morning as my husband and I drove through a nearby town. We were in college, and as we were both new to Iowa, our Saturday mornings often involved exploring the surrounding towns. On this beautiful spring morning, we passed a small house, and a distinct memory lingers. An older gentleman sat in a lawn chair beside his garden, the details etched in my mind: his pressed, short-sleeve button-up shirt, his snapback farmer hat, and most vividly, the line of colossal cabbages standing proud along the garden's edge.
Maybe it was because this sight was so quintessentially Iowan and it fed my growing love for the state, maybe it was a foreshadowing of my life to come, but for nearly 20 years I’ve been carrying around this memory of an old man and his impressive cabbages and for twenty years I’ve been trying to live up to it with my own cabbages, most of the time falling short. That is until this year when I finally grew some cabbages that I think the old man would be proud of. Well, if he knew I existed of course. Don’t get me wrong, I’ve grown many fine cabbages—that part is straightforward—but until now, not the scale-tippers I was wanting. Anyway, now that I’ve checked this one off my list, I’m excited to share what I’ve learned. So, let’s get to it!
My beautiful baby sitting beside our toddler. Just kidding, the kid's cute too--I grew him as well.
What's the big deal?
Reading that introduction may have you thinking that cabbage is hard to grow, but I want to be careful not to give that impression. Due to its classification as a “refined” Brassica, cabbage does have a reputation of being a prima donna, however, I think this reputation is, at least to some extent, undeserved. If you plant your cabbage seeds and provide the most basic level of care (weeding, occasional watering, insect protection) your seeds will produce cabbages. They may not win any contests, but they’ll still be far fresher and tastier than anything you could buy from the store, and in the end, isn’t that what we’re all after?
Choose a prime planting site
While many vegetables will be content pretty much anywhere in the garden, Cabbages are a bit more picky in terms of their location. As mentioned previously, most soils will grow cabbages, but highly fertile soils will grow the largest cabbages. Therefore, reserve the most fertile spots in the garden for your cabbages, keeping the following preferences in mind.
Improve soil fertility
Cabbage is a very heavy feeder that needs rich, fertile soil with a pH of 6.0 to 7.5. Gardeners will do well to amend the site with a heavy dose of compost or well-rotted manure prior to transplanting. This serves two purposes: 1. It increases the amount of nutrients available to the plants throughout the growing season and 2. It regulates the moisture content of the soil, which will be very important as the heads begin to swell. If your soil has a decent amount of organic matter, but is not of the highest fertility, a teaspoon of 10-10-10 fertilizer mixed into the bottom of the hole at transplanting time will do the trick.
allow lots of sun
Choose a site that receives at least 8 hours of sun daily. Cabbage can survive with less but will produce the largest heads when it can bask in plenty of sunlight. In areas where the temperatures can get quite warm in late spring and early summer, some light shade may be beneficial.
select the right variety
Variety selection is key when attempting to grow mammoth cabbages. While there are many delicious early and mid-season varieties out there, it’s the late season varieties that will yield the largest heads. These varieties are slower growing and form dense, tightly packed heads that hold up well during storage. They are also less prone to splitting as they size up, which allows them to grow later into the season. Danish Ballhead and Savoy Perfection are some of our favorite late varieties for growing large cabbages. Although technically a mid-season variety, All Seasons excellent standing ability makes it a great option as well.
Hybrids vs. Heirlooms
While we are firmly in the heirloom camp, I will concede that hybrid varieties are going to give you the largest heads. Don’t let that discourage you from growing heirloom varieties though—it’s not all about size. When it comes to hybrid cabbage, flavor seems to have been an afterthought in the decades-long pursuit of durability and uniformity. This is just my opinion, and many of you may beg to differ, but my experience with popular hybrids like Megaton and Stonehead is that flavor seems to be lacking when compared to my favorite heirlooms. None of this changes the fact that hybrids will indeed give you the largest heads, and if you’re looking to win contests, that may be what you’re after.
Sow (and transplant) early
Regardless of whether you’re growing a hybrid or heirloom, the key to growing large cabbage heads is to get the seeds started early and the seedlings transplanted outdoors while the weather is still cold. The latter part of that statement is key. Starting your plants too soon and then not being able to transplant them will do you no good. As an example, here in Iowa our last frost usually comes around May 10th. I like to get my cabbage seeds sown the first week of March (10 weeks before last frost) and I aim to have them transplanted the first week of April (6 weeks before last frost.) Usually, my garden must be prepped in the fall to get this to work. There are many years where I don’t have it all together and need to work the garden in the spring. That’s alright, I can still grow nice cabbages and they still taste great—I just don’t get as large of heads as I do when I transplant them early. In milder climates, cabbage can be sown much sooner. Southern gardeners, for example, often aim to have their spring cabbage sown on January 1st.
give them room to grow
Transplant your cabbages outdoors as soon as the soil can be worked. As mentioned earlier, I like to have them in around 6 weeks before the last frost, but any time in spring will work. One week before transplanting, bring the seedlings outdoors during the day so that they will be sufficiently hardened to those cooler spring temperatures. Prepare the beds by working in a good bit of well-rotted compost or manure. Alternatively, place a teaspoon of 10-10-10 into the bottom of the hole before transplanting. Set seedlings at least 24 inches apart. This will look generous early on but remember they’re going to get huge. Burry them only to the natural soil line as burying deeper could lead to issues with rot and disease.
My general process for transplanting is to dig the hole and fill it with water, then dangle the seedling in and backfill as quickly as possible. This creates a giant mudball around the roots which will keep the seedling happy until the next rain comes. I seldom have to water after this, which is good because I’ll be busy planting for several more weeks and won’t have time to come back and water each day. Regardless of whether you use my method or not, you’ll want to make sure the seedlings have plenty of water until they’re established.
Feed 'em Well
As mentioned before, cabbages are heavy feeders, so you’ll want to fertilize regularly if you haven’t already amended the soil. Side-dressing or liquid fertilizing cabbages can begin around three weeks after transplanting and continues every couple weeks until the heads begin to form. During this period of growth, it's also important to note that cabbages have shallow, dense root systems which are easily damaged by garden tools while weeding or cultivating. For this reason, it’s best to mulch thickly around the plants to minimize the amount of weeding that is required. This also helps to regulate soil moisture and cool the soil which will, in turn, allow the cabbage heads to grow larger without splitting.
keep pests at bay
Early on, cabbages are susceptible to predation by animals, and particularly rabbits. Be sure to put protection around the young plants to ensure that your hard work isn’t wasted in a mere moment by some hungry bunny. Milk jugs or cheap plastic cloches work well for this purpose. Additionally, young cabbage plants can be susceptible to flea beetles. We’ve had good luck using Safer’s Insect Killing Soap (no commission earned) to control flea beetles. Note that you must spray regularly keep the population at bay.
By far and away the most challenging part of growing cabbages is to keep the cabbage moths off them. Nothing is more frustrating than peeling your gigantic cabbage and finding that a cabbage worm has bored itself inside—such an event can elicit foul words from even the most restrained tongue. There are a number of methods to keep these pesky insects at bay. Dill and onions, for example, when planted by cabbage, are known to repel cabbage butterflies. Additionally, Bacillus thuringiensis (Bt), a popular biological control, kills the catepillars when small amounts of it are ingested from the surfaces of leaves. We’ve had good luck using Dipel, a powder form of Bt, however it is important to note that applications must be made regularly. Falling behind in your regimen could result in one of these buggers sneaking in at the last minute.
Durable "staple" cages provide effective protection against animals and flying insects.
fortify if needed
The only surefire way to protect your cabbages from cabbage moths and their crawly green offspring is to cover the plants. We implement a system that utilizes inexpensive half-inch conduit which is bent into “staples” that support the weight of the row cover. A 10-foot section of conduit will make one staple that is roughly 3-foot wide by 3-foot tall, just the right size to span a bed and provide a bit of vertical space for the plants. The bending can be done by hand using a cheap conduit bending tool and the structures, once finished, will last for decades.
Once formed, we straddle the staples over our beds and push them in the ground about 6 inches deep. We place the staples about 5 feet apart and then run a straight piece of conduit down the line of staples to fasten them all together. The resulting cages look, somewhat ironically, like giant caterpillars. You can use Remay or some other lightweight covering to close them in. Greenhouse clamps work well for keeping the fabric in place. Pro tip: Buy clamps that have rounded edges as pointy corners can tear the fabric in high winds. Some people like to bury the edges of the fabric, but we find that burdensome when checking and harvesting our cabbages. Plus, cabbage moths may look graceful, but they aren’t stealthy. In other words, they aren’t going to exploit small openings in your covering, especially when located near the ground.
watch them closely
Cabbages are ready to harvest anytime after the heads reach the size of a softball, but if you’re reading this article, softballs aren’t what you’re after. Just make a special note here: Which kind of cabbage you’re growing will determine when it must be harvested. Early cabbages, for example, get touchier the larger they get and should be monitored regularly, lest they split suddenly after a soaking rain. Mid and late season cabbages can be left out for longer. Some varieties like All Seasons seem perfectly content to sit in place until you’re ready to use them. Still, you should keep an eye on them to make sure they don’t pass their prime. If you find that one has split, use it immediately. It will still work fine for coleslaw or sauerkraut, but it won’t store well.
Once you’re ready to harvest, you can either cut the head or snap it off by reaching in and grabbing the head where the leaves are held firm and tight. Give it a good, quick twist and it should snap off. Alternatively, if you intend to store your cabbage for some time before using it, you may prefer to pull the entire plant up from the roots. Heads up (pun intended) this is not an easy task. If it doesn’t come easily, plunge a spade into the ground beside the cabbage to free some of the roots. Be careful not to damage the heads as blemished heads will not store well. Remove the loose leaves, gather your wheelbarrow and cart that heavy monster indoors—it’s time to celebrate!
Wait, it's not over yet!
I know this article is about growing large cabbages, but I just can't talk about harvesting cabbage without including this interesting little tidbit. If you elected to use the first approach to harvest and snapped the head off just below the tight wrapper leaves, you’re in for a surprise. Those larger leaves you left in place are going to give the cabbage plant a second chance at life. With a thorough watering, you should soon notice three or four mini cabbages being formed around the stump where you just harvested. Left alone, these little cabbages will form heads about the size of baseballs. They won’t get firm enough to store, so pick and eat them as needed. One way to prepare them is to quarter the heads, boil, and then coat with butter before serving. Boiled and buttered mini cabbages are quite a delicacy and will have your dinner guests feeling very special under the impression that you harvested your cabbages early just for the occasion. You don’t need to tell them they’re technically eating the remnants of last month’s coleslaw.
Well, there you have it—twenty years of trial-and-error culminating in lots of lessons, countless quarts of sauerkraut and a few colossal cabbages. I hope you’ve found this article useful and that upon reading it, your cabbage dreams won’t be so far off. Feel free to poke around our website and check out more growing tips, gardening stories, and of course, some awesome heirlooms.
Becky Weeks, Ph.D.
Geneticist, Gardener, Founder of Thresh Seed Co.
Becky is a geneticist with a passion for gardening. Prior to starting Thresh Seed Co., she spent fifteen years researching plant genetics and development, later applying those principles to aid in the breeding of commercial corn and soybean varieties. She lives on a farm in Iowa with her husband and three children, where she enjoys growing just about anything and experimenting with the breeding of new vegetable varieties.