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Growing Great Broccoli and Cauliflower
February 15, 2015

Growing great broccoli in our climate region, along with most of the other brassica or cole crops, is just a matter of working with the weather to produce crops before and after the real heat of summer. Here in west central Indiana, we're able to grow great spring and fall crops.

Broccoli and cauliflower are heavy feeders, but don't really require ones very best garden soil. While we grow delicious brassicas in our raised beds with their improved soil, we've also grown pretty good broccoli in our East Garden with its heavy clay soil. The trick with brassicas seems to be improving the soil around each broccoli plant a bit, feeding it well, keeping bugs off the plants, and beating hot weather.

Transplants

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We grow our spring brassicas from transplants that we start in February. Actually, we now grow all of our own transplants. We start more transplants inside during the heat of summer in June or July for our fall crop. While many vendors sell rather expensive plant racks and lights, we still use a wooden plant rack I built in the late 1970s with simple fluorescent shop lights to nurture our transplants.

While the photo at right shows a box for a plant and aquarium fluorescent tube, we generally use 5600° K and/or 6500° K fluorescent tubes for our plant lights, as they approximate daylight a bit better and are far cheaper than the plant fluorescent tubes.

A major advantage in growing ones own transplants is being able to choose from the many varieties offered by reputable seed houses, rather than just one or two offered by a garden center or other outlet. A second advantage is being able to time ones transplants to be about six to eight weeks old at planting time, an ideal growth stage for transplanting brassicas. One may even save some money by growing their own transplants over purchasing them, although with the cost of seed, potting mix, inserts and trays, and the lighting equipment, I'm not sure.

Starting broccoli, cauliflower, cabbage, and in our case, occasionally Brussels sprouts and kohlrabi, is pretty easy. Brassica seed germinates well in the dark without any bottom heat.

We start our plants in standard 1020 seed flats in #804 or deep #606 inserts from the Greenhouse Megastore (DGW rating). While those terms may sound like gobbledygook, it means I use plastic inserts that give me 8 fourpacks of cells which equal 32 planting cells per seed flat or six deep cells per insert which equal 36 cells per seed flat. Such insert cells hold enough soil to adequately nourish transplants such as brassicas, tomatoes, peppers and such for six to eight weeks growth from seeding to transplanting. Keeping the plants in such small quarters any longer than that risks stunting their growth.

I usually use a slotted seed flat for drainage directly under the inserts with a solid flat (no holes in the bottom) underneath the slotted tray to catch runoff. The second flat also adds a little strength to the combined flats, although in recent years I've also begun using a slotted tray with a heavy-duty Perma-Nest tray underneath it. For smaller plantings, I use some old half flats that hold four, four cell inserts.

We wash and reuse our seed flats and inserts year after year until they split, crack, or get stepped on.

Since brassicas transplant quite well, one could also start their broccoli (cauliflower, etc.) with a dozen or so seeds in a single pot, transplanting the seedlings when they've emerged and put on their first true leaves into larger, individual pots or four- or sixpacks. As long as the plant container has enough room for root growth and good drainage, the plants don't seem to mind what they're in.

I fill the inserts with sterile potting mix, often on our back porch on a nice winter day, and firm the soil with my hand. I water the potting mix with warm water, as the peat moss in our starting mix doesn't readily absorb cold water. Sometimes I water the whole flat before seeding and split away the bottom solid tray for a time to let excess water drain. At other times, I seed into dry soil, pull the slotted flat up, and bottom water the trays, later draining any excess water. Either way, I have to warm the water used on our stove, as our hot water is soft water that contains some water softener salt. The small amount of salt in soft water probably wouldn't hurt the plants, but it's one more thing I can do to ensure good germination and growth.

The seeding process is just a matter of making a shallow indentation in the center of each insert cell with a finger or thumb, popping in a seed, covering the seed with a little sterile potting mix, and firming the soil with a touch of a finger to ensure good seed to soil contact. I often add an extra seed here and there at the corner of a cell in case some seeds don't germinate. I label each insert with a plastic plant label with the variety name. We cut costs by reusing the plastic plant labels year after year, soaking them in a bleach solution to remove the permanent marker ink on them. Surprisingly, the labels last four or five years before becoming brittle and snapping in half!

The planted flat of brassicas is covered with a clear humidity dome to hold in moisture and goes onto a shelf on our plant rack. While light isn't needed to germinate brassicas, I want the plants to begin getting light as soon as they emerge (four to six days, usually). Once our transplants have pretty well all germinated, we remove the humidome and quickly get our plant lights within a few inches of the tops of the plants. Our brassicas are often a bit spindly at first, and sometimes I have to carefully uproot them, moving them deeper into the soil without injuring the plants to correct the initial legginess.

We generally (bottom) water our plants about once a week after they germinate with about a half gallon of water per planted seed flat. In three to four weeks, the plants are big enough to be moved outside under our cold frame.

Note that I often start our cauliflower two to three weeks before our broccoli to accommodate its generally longer days-to-maturity.

Hardening Off

At four to six weeks old, brassicas may appear to be big enough to go into the garden, but they're not quite ready yet. The plants have to gradually become acclimated to the harsher growing conditions of the great outdoors. Putting them under a cold frame keeps the plants a bit warmer (a lot warmer with the top down) and protects them from the full sun, UV radiation, and wind. Opening the cold frame for gradually longer periods each day allows the plants to toughen their stems. Gardeners lacking a cold frame can harden off plants in sheltered areas of a porch or similar area.

After a week to ten days, if I'm not ready to transplant our brassicas, they go on the edge of our back porch, fully exposed to the sun, wind, and rain...and do just fine there. I do have to remember to water them regularly.

Warning: Leaving plants under a closed cold frame on bright sunny days can cook ones transplants. A good cold frame will trap enough heat to shoot interior temperatures well over a hundred degrees on such days. Been there, done that, and I didn't even get a T-shirt, but I did kill a lot of transplants!

Preparing the Bed

Gardeners work with the soil they have, hopefully improving it gradually over the years by adding compost, well-rotted manure, peat moss, and/or turndown crops. But whatever soil one has, it's important to loosen the soil before planting or transplanting by rototilling or using a shovel, garden fork, and/or garden hoe. While doing so, one can work in any soil amendments necessary. Soil pH for brassicas should be around 6.8-7.0. Lime to raise soil pH is best added in the fall to give it all winter to work. One can use ground limestone in the spring, which works more quickly than granular limestone to adjust soil pH. Sulfur can be used to lower soil pH, something we in the midwest only do when planting potatoes and such. A general fertilizer such as 12-12-12 can be lightly broadcast over a planting bed and worked in while tilling.

An inexpensive soil test meter for soil pH is a good investment. They're fairly accurate and last for years.

We save ourselves a lot of grief by fall tilling our garden plots, especially those that will be used early in the spring for early peas and brassicas. We still find spring tilling necessary some years, but get away with just a good hoeing and raking other times.

Transplanting

Broccoli and cauliflower get bitter and go to seed in the heat of summer here, so our brassicas are always the first plants we move into our garden. Since brassicas can withstand a light frost, we usually get our broccoli, cauliflower, and cabbage transplanted in early April, although they've gone in as early as March 24 and as late as May 25 in the spring. But over the last few years, we've found planting during the first week of April to be about the right time to transplant in our area.

Once any necessary soil preparation is done, our brassica area is raked smooth and stakes and string are added to assist in getting our rows straight. I use a wide garden trowel to dig a planting hole as deeply in the soil as I can (about 6-8"), loosening the soil at the bottom of the hole as much as possible to promote deep root growth. Then the transplanting hole gets a quarter handful of 12-12-12 commercial fertilizer and a sprinkle of ground calcitic limestone to fend off clubroot. (In areas with alkaline soil, ground egg shells can be used to supply the calcium necessary to prevent clubroot.) I use my trowel to work both into the soil a bit. Then I fill the hole with dilute transplanting solution (about half strength Quick Start, with a bit of Maxicrop Soluble Seaweed Powder mixed in).

When I grow broccoli in our East Garden plot, I use a shovel to make planting holes. I mix in compost, peat moss, fertilizer, and lime. Doing so creates one foot wide and deep areas of good soil in the lousy soil of that plot.

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Once the starter solution has soaked into the soil a bit, I backfill the hole with the soil I dug earlier and plop a cutworm collar into the soil and water the cup. Since we have problems with cutworms in our garden plots, I use old, waxed paper coffee cups with the bottoms cut out as cutworm collars. Left in place for a week to ten days at about an inch above the soil line, the cups prevent cutworms from attacking the still tender brassica stems.

Then I squish my transplant into the cup, backfilling with a bit more soil around the base of the broccoli stem. I use my fingers to firm up the soil and again water generously with starter solution.

In our current raised beds, we space our broccoli plants about 18-20 inches apart in the row, leaving anywhere from eighteen inches to three feet between rows, depending on where and what bed they're going into. When planting into our narrow raised beds, a close row spacing of 18-20 inches is necessary, as the bed is only 36" wide, and I may want to edge it with flowers or spinach. When planting into our main raised bed or our East Garden with more space, I often leave two to three feet between rows of brassicas. I get away with the closer row spacings in our narrow beds because I only plant two rows of brassicas together, allowing me to work the plants from the outside of the rows. If one is going to plant more than two rows, a spacing of 30-36" between rows allows one to work the rows and later harvest the crop without damaging plants.

When I can, I try to space our cauliflower and cabbage a little more in the row, as those plants tend to spread more than broccoli. But more often than not, I'm cramped for space and space them about the same as the broccoli.

An optional, but for us, necessary, step in the planting is to spread some homemade smelly, nasty tasting stuff on the plants and ground to discourage rabbits and deer from nibbling on the plants. It also keeps our dogs, usually, from digging up the transplants or laying on them.

Care Through the Growing Season

About a week or so after transplanting, I'm able to remove the paper cup cutworm collars from the transplants. I use a quality pair of kitchen shears to cut down both sides of each cutworm collar. Then placing fingers on the soil on either side of the plant stem, I very gently pull each half of the cup up and out of the ground. I firm the soil to fill in the space the paper cup occupied and water the plants.

If I haven't already, I begin mulching our brassicas with grass clipping mulch. It holds in soil moisture and mostly prevents weeds from germinating under the plants and in the rows between them. The mulch breaks down in time and has to be replenished at least once before harvest. But as the mulch breaks down, it also adds nutrients to the soil. With mulch, we don't have to water our brassicas once they get established.

Depending on how fertile ones soil is, you might be able to get away without any additional fertilizer until harvest. But brassicas are heavy feeders, so pulling back the mulch and working in a bit of balanced fertilizer and/or compost around the base of plants can give them a boost.

Insect Problems

Once you get past the danger of cutworms at planting, there is another major insect problem with growing brassicas. The worms from cabbage loopers or small white cabbage moths can make brassica leaves look like someone blasted them with a shotgun while also seriously damaging the heads. The moths lay their eggs on brassicas and when they hatch out, the worms have a ravenous appetite.

The safest, best prevention for such insects are products such as Thuricide and Dipel that contain the biological, bacillus thuringiensis (BT). Unlike typical poisonous insecticides, BT acts by producing proteins that give the bugs fatal stomach cramps. Their digestive system gets paralyzed, and the infected insects stop feeding within hours and generally die in a few days.

We spray with Thuricide throughout the gardening season to keep our broccoli, cauliflower, cabbage, and kale fairly worm free. BT is considered safe to people and nontarget species such as wildlife. And it can be used on a variety of food and other crops. We've had some success using Thuricide to prevent bag worms from attacking our Blue Spruce trees.

As with all controls, BT sometimes fails. When that happens, usually about once a growing season with our kale, I have to break out some stronger stuff to vanquish the nasty worms.

Critter Damage

Both rabbits and deer can devastate a planting of brassicas. Rabbits will eat new transplants right off to the ground. Deer wait a little longer, biting the tops off of broccoli plants when the plants are about a foot tall. As mentioned earlier, smelly, bad tasting stuff is often enough to discourage critters.

Even with the best preventions, though, you sometimes lose. Several years ago, rabbits ate every one of our fall brassica transplants right off to the ground. Only a couple of the plants recovered and regrew from the roots, although we still got a small crop of broccoli by direct seeding.

Buttoning

Buttoning is the failure of broccoli plants to produce heads or producing small heads prematurely. We'd seen a bit of buttoning every now and then in a plant or two in our garden. In the spring of 2016, seven of the ten broccoli transplants I'd set out buttoned! Stress is listed as the cause of buttoning on most sites, with cold temperatures, poor soil fertility, root bound transplants, dry soil conditions, and excessive salt in the soil all being mentioned.

Plants that have buttoned can be left in the ground to possibly produce sideshoots later on and may even put on some small but usable heads.

Harvest

In a good year, the broccoli we transplanted into our raised beds in early April begins to mature good heads in mid-May. The leftover transplants we put in later in our East Garden put on main heads in June. Our cauliflower with its longer days-to-maturity begins to come in about a week or two after the broccoli. But both crops can defy days-to-maturity figures due to weather conditions, coming in either early or late. And broccoli, once it sets a head, can mature very quickly, making daily checks of the crop important.

We cut our broccoli when the heads are still tight and a nice blue-green color. Waiting until the buds begin to open into yellow flowers or the head browns a bit ruins the broccoli. We take our cauliflower heads when they're just a little bigger than a softball. Once the leaf wrap around the cauliflower begins to spread, it's time to cut it, as sunlight will cause the heads to yellow and turn bitter. Since we grow varieties that have been standardized for a concentrated commercial harvest, our broccoli tends to come in all at one time. Since broccoli freezes well, that's not a real problem.

The actual harvest of the broccoli and cauliflower is done the same way. We use a sharp kitchen knife to cut just below the heads. Once cut, the cauliflower plants come out of the ground to be composted. Broccoli plants are usually left in the ground and even fertilized a bit. They will begin to put on smaller sideshoots (mostly quarter sized heads, but sometimes larger) that can extend ones picking season for several weeks. As long as the weather doesn't get too hot, the sideshoots should be as sweet as the main heads. They're just smaller, take a bit of hunting to find, but there should be lots and lots of them.

Varieties

Brassica varieties seem to come and go over the years as seed producers move on to newer hybrid varieties. And varieties that grow well here in the midwest may not grow as well in other regions.

We're not exactly on a hot streak with our brassica varieties, as several of our favorites have disappeared from the market in the last few years. Having said that, our longtime favorite broccoli was Premium Crop. I still have a precious packet of seed of the variety in the freezer. We also have had good luck with the Castle Dome variety.

The open pollinated Goliath variety from Stokes Seeds also produced large heads for us, again with a concentrated set, something not always wanted by home gardeners. Stokes dropped the variety, so I began trying to save seed from it in 2019. Our first try was a bust, but we got a nice crop of Goliath seed in 2020. Other seed houses carry broccoli seed named Goliath or Green Goliath, but they never did as well for us as the Stoke's strain of Goliath. Some heirloom varieties such as De Cicco produce smaller main heads spread over a longer period of time, followed by many sideshoots. We've not had much luck growing De Cicco, though.

Our favorite cauliflower is an open pollinated variety, Amazing, that self-wraps its leaves to keep heads from yellowing. Dedicated seed savers should keep that variety around forever. Fremont is a good producing hybrid if you can find seed for it. It has been replaced in some seed catalogs by the Bishop variety. And we "discovered" the old Violet of Sicily variety years ago that we really like. It produces medium sized heads that turn reddish at maturity. Note that Violet of Sicily seems to be available from some vendors under similar names (Purple of Sicily), but you'll know it by its appearance in pictures in seed catalogs.

Some cauliflower varieties aren't self-wrapping or self-blanching. To keep heads from yellowing, one needs to wrap leaves over the head of the cauliflower fairly early on (when the head measures about 2-3 inches across). One can hold the leaves in place with a clothes pin, rubber band, twist tie, or what have you. I've tried such varieties a few times and would definitely recommend using a self-blanching variety!

Other Brassicas

We don't grow a lot of cabbage in the Senior Garden, but what we do grow is usually Alcosa savoy, Super Red 80, Tendersweet, and on occasion, the tried and true open pollinated Early Jersey Wakefield.The same goes for kohlrabi, but we use Grand Duke.

Our favorite kale is Vates (also called Dwarf Blue Curled or Dwarf Blue Scotch). It's been our standard kale for years and is a solid producer with very good flavor. We also grow some Lacinato and Red Ursa. We direct seed our kale, spring and/or fall, as it doesn't seem to transplant as well as other brassicas. Getting fall kale started in our hot, dry, July weather can be a challenge, requiring daily watering.

Possibly because it's not one of my favorite vegetables, we don't grow a lot of Brussels sprouts. Our current seeds are the Dagan and Hestia varieties.

Fall Brassicas

Other than the timing, we grow our fall brassicas just as we do our spring broccoli and cauliflower. We start our transplants inside in late June while we're still feasting on spring broccoli and cauliflower. After hardening off, the plants go into the garden in late July or early August. (Note that I do rototill the bed before transplanting, adding a good bit of compost and/or fertilizer.) We experience a lot more rabbit damage with our fall brassicas just after transplanting, though.

We also have to water our fall transplants a few times to get them established mid-summer, as the soil in our raised beds gets pretty dry by July. Getting grass clipping mulch around the transplants as soon as possible reduces the need for watering. When mulching right after transplanting, care must be taken to not let the mulch form a ramp up to the tops of the cutworm collar cups, as cutworms will gladly march up it and consume your precious transplants.

With fall cauliflower, it's especially important to allow at least two to three weeks more than its days-to-maturity before the first expected frost. Fall planted crops grow more slowly in the shorter days of fall. We've flat out missed on this one several times, getting good fall broccoli, only to lose our fall cauliflower to a hard freeze a week or so later.

Saving Brassicas

While we've canned and frozen vegetables for many years, I feel a little on thin ice on this section. When we put up broccoli, cauliflower, or any other brassica, we scrupulously follow the directions in the Ball Blue Book Guide To Preserving. It is the essential source about safe canning, freezing, and other methods of preserving.

With the cover of our old Blue Book tattered and falling off, my lovely wife got me the new Ball Complete Book of Home Preserving for Christmas 2021.

After cutting broccoli or cauliflower and washing and stripping off the leaves, we soak it in salt water for half an hour to kill off any worms that have survived our efforts with BT. Then we cut the broccoli or cauliflower into florets or individual mini-heads, leaving a bit of head with several inches of stem to be frozen. Even with our best efforts at insect control, we often find a dead worm or two to be disposed of hidden in the florets.

The broccoli (or cauliflower) then has to be blanched or scalded for 3-5 minutes to kill off bacteria that might be present. At the end of the blanch, we quick cool the brassicas in cold water before drying. I just spread the broccoli out on a clean kitchen towel for drying.

While one can stuff the broccoli into a freezer bag at that point, I prefer to spread the broccoli out on a no-stick cookie sheet or one treated with spray cooking oil for freezing. That makes taking a few florets out of the freezer bag a bit easier later on.

Once the broccoli or cauliflower has frozen on the cookie sheet, I put the florets into a gallon Ziplock Freezer Bags, squeezing out as much air as possible before zipping them shut. Then the bag goes into our big, manual defrost freezer in the garage.

Most of our kale gets used fresh or in our Portuguese Kale Soup. When we're able to freeze some, it gets soaked, stemmed, inspected for worms, boiled, and frozen with liquid in pint freezer bags.

Let me insert a commercial note here. I use a Tramontina 8-Quart Multi-Cooker for such blanching and a lot of other things. It's one of the very few, expensive pieces of cookware I use. I bought ours over ten years ago when the cost was about half of what it is today. Unlike some cheapie cookware, the pot is quite heavy, which helps spread heat evenly and prevent burning along the bottom. The set comes with two strainer/steamers. I love ours.

Having written all this stuff about freezing, I need to add that frozen brassicas are a poor second best to fresh. We love steamed broccoli, cauliflower, and carrots with garlic, seasoned salt, and lots of butter. But there's nothing quite like fresh broccoli, cauliflower, or kale. (Note that I'm writing this update in the dead of winter, just after we used up the last of our frozen kale!)

Help with Timing Crops

Several years ago, the folks at Johnny's Selected Seeds began publishing a page of Interactive [Garden] Tools. I find their online Seed Starting Date Calculator and their Fall Harvest Planting Calculator spreadsheet (589K download) especially helpful in timing planting or starting transplants. They're free and easy to use.

Final Thoughts

Broccoli may have been the first garden crop I really mastered growing well. It's either that easy, or I just got very lucky over forty years ago. I didn't grow good cauliflower until about ten years ago, helped along greatly by the advent of self-wrapping varieties. And "mastered" may be a relative term, especially when you see an open garden plot where rabbits have eaten every transplant you painstakingly put out. Or, when you get greedy and decide to let a gorgeous row of broccoli plants go a few more days to reach soccer ball sized heads...and it all goes to seed the next day.

Gardening for me has been a lifelong learning process. It began as a five-year-old following my grandfather around his one acre garden in then rural Indianapolis (really in Nora, for folks familiar with Indy). I began my own garden plots in our back yard before my teenage years, growing strawberries and sweet corn. When we had our first house with a yard, our landlord and my former foreman on the loading docks loaned me his rototiller and his Burpee Seed Catalog. I've been lost forever after in the wonder of gardening.

Having said all of that, just because a retired, old guy has a web site on gardening doesn't mean he knows jack about it. I have absolutely no degrees in agriculture or horticulture or any other special training. At 73 years old, I'm still happily learning, so there could be tragic errors in the information above. It's just what has worked for us.

From Steve Wood, the at Senior Gardening