Nothing makes a gardener feel like they know what they're doing quite as much as beautiful, plump heads of cabbage nestled in the center of vibrant, lush, huge-leaved cabbage plants. Unfortunately, cabbage sometimes fails to head, and getting those perfect lumps of leaves to grow tightly bound and ready for the kitchen can require some finesse. 

This versatile vegetable is a biennial, meaning that it grows and stores energy one year and then reproduces by flowering and making seeds the next, but we grow it as an annual for the tasty heads. It's a Brassica, like kale, collards, broccoli, or cauliflower. 

The heaviest cabbage, holding the world record, was 138.25 pounds and was displayed at the 2012 Alaska State Fair by Scott Rob. Your cabbages may not be that big but correct these problems, and you'll be on your way to delicious, well-formed heads yourself. 

Reasons Your Cabbage Didn't Form a Head

After caring for cabbages for weeks, it's frustrating when they don't make a head. There are several possible reasons, and sometimes, they combine simultaneously. For instance, your cabbages might suffer from low nitrogen and inadequate water.

Cabbage is a cool-season plant and doesn't do as well in the heat of summer. Most gardeners have the best results with an early spring planting for an early summer harvest or a midsummer planting for an autumn harvest. Locations with more temperate, short summers and cool nights may be suitable for summer cabbage growing, with care.

Setting cabbage up for success involves planting at the correct times, choosing varieties well-suited to your local climate, finding a sunny spot, providing well-drained soil amended with aged manure or compost, and mulching. Add a midseason nitrogen boost, and you're well on your way to crunchy, firm, delicious cabbage heads.  

When choosing varieties, select early and midseason cabbages for spring planting and late-season or storage varieties for the fall crop you'll plant in late summer. Early to mature cabbage will be headed and ready for harvest before the heat of summer arrives. Fall storage varieties planted in summer (perhaps with afternoon shade) will be ready just in time for cold weather and winter storage. 

Bolting in Hot Weather

Cabbage loves those days before—or after—the heat of summer. When subjected to hot, sunny weather, it may bolt. When cabbage bolts, it sends up a stalk and flowers and won't produce a head. The stress of the hot weather causes the plant to attempt to reproduce, even though it isn't ready. You've seen this stress-induced response likely in other plants, like when a young tomato seedling puts out one tiny flower, even though the plant is only a few inches tall. 

While cabbage plants love full sunshine in cooler months, you may be able to squeak a few more weeks of growing time in summer by choosing a location with afternoon shade. A perfect way to accomplish this is by planting cabbage in full sun and then planting taller vining crops on a trellis to their south and west. The cabbage will get morning and midday sun but get some relief from the hot afternoon rays. Buildings that cast afternoon shade like your or a neighbor’s garage can also serve this purpose.

Cold Weather and Young Plants

Cold weather at an inopportune time can also make a cabbage bolt. While large, mature plants are quite tolerant of lightly frosty temps, young plants are prone to bolt if temperatures stay below about 45℉ for an extended period of time. Cool nights and warm days are no problem, but consistent cold weather, like when an unscheduled cold snap lingers for a week in late spring, can cause issues. 

If your weather is getting squirrely, protect young cabbage plants by covering them with an upside-down bucket overnight or some frost cloth for an especially cold night or two. 

Pest Damage

Pests like caterpillars, deer, or other insects can damage the central growing point on a cabbage plant, causing the plant to grow large, make big green leaves, and never produce a head. If this problem sounds familiar, cover your next cabbage planting with a fine net until the heads start to set, to keep problem pests at bay.

While aesthetically unpleasant, damage to the outer leaves from other leaf-munching pests normally will not cause a failure to head unless the defoliation is severe. However, those same pests can bore into the head, making it less desirable for the kitchen.

Nitrogen—too much or too little

Cabbage loves nitrogen. As a plant nutrient, nitrogen is responsible for helping with green, leafy, vegetative growth. You may be familiar with the issue of excess nitrogen in tomatoes, causing huge plants, but little set fruit. Well, the same can happen with cabbage. While we want large cabbage plants with many leaves, there can be too much of a good thing. 

Too little nitrogen available will cause stunted growth and possibly yellowed leaves, just like with other garden vegetables. Work in compost or aged manure at planting, and then side-dress with fertilizer partway through the growing season, but don't go overboard. 

Water—too dry or too wet

Water is one place where a little preparation will help with late-season issues. Too little water and dry soil will cause slow growth and late, little, or no heads. It makes sense—they need water to grow like any plant. 

However, too much water can cause issues with root rot and splitting heads, even when small. Just like inconsistent soil moisture can cause a tomato to crack, it can also happen with cabbage. 

To help eliminate the problem, get a rain gauge and use compost. Adding a rain gauge will help you monitor rainfall and irrigation more closely. You’ll know when to water if there hasn’t been enough rain, or when to hold off. Of course, test the soil moisture with your finger for another good indicator.

Compost will add soil organic matter, which helps with drainage and soil moisture. Compost increases pore space in heavy soils, allowing water to percolate down, creating well-drained soil. Think of how dense clay soil is, with very low pore space—water has trouble moving around. Compost also absorbs soil moisture, holding it and releasing it later (along with nutrients), providing a slow-release boost to soil moisture. 

Club Root

This soil parasite causes extreme swelling of the roots, impairing their function. All brassicas are susceptible to this disease. Club root-infected cabbages will have stunted growth and wilt easily, even under normal moisture conditions. Proper garden sanitation will help to minimize this issue.

Overcrowding

Like all plants, cabbages won't perform as well without sufficient space. A cabbage plant can easily stretch two feet across if not more! Many gardeners succumb to the temptation of planting cabbages closely together. It can look like an awful waste of space to plant cabbage seedlings 18–24" apart in rows three feet apart. But, they need the space.

While plants can be tucked in a bit tighter, keep in mind that severely overcrowded cabbages aren't able to get the sunlight and nutrients they need in sufficient quantities to make all that vegetation and form a head. It takes a lot of energy to make those large, dense heads we’re after. 

Time

It sounds too simple, but some cabbage varieties take practically forever to mature. If you've been growing Katarina Hybrid with a 55-day maturity, and then you switch to an excellent keeper like Premium Late Flat Dutch, it may seem like your cabbages aren't heading out when they just need more time. Many cabbages bred for long-term storage don't mature for 100 days or longer. If the center growth point hasn’t been damaged, and the plant is healthy, stay patient. It’ll eventually make a head.