Hollow Stem

If you grow members of the cabbage family, you need to know about hollow stem.


Hollow stem is a physiological condition that occurs within the main supporting stem that holds up your cabbage, broccoli, or cauliflower. At first, small cracks develop in the center of the main stem. As the stem grows, the cracks enlarge, creating cavities that are prone to pest infestations and disease, especially rotting.


If you cut open the stem of a plant that seems affected by hollow stem, the damage is obvious.

Cauliflower with hollow stem (UMass Extension)

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Causes of hollow stem

Too much nitrogen and hot temperatures are a bad combination for cole crops. The nitrogen causes rapid growth, but the heat puts too much strain on these cool weather crops. As cracks develop within the stem, pith is lost and the stem becomes weakened. This allows pests and disease to enter, damaging your harvest.


Hollow stem and boron

For many years, boron deficiencies were blamed for hollow stem. We now know that this is not true. If there is a boron deficiency and hollow stem has occurred, you will be able to see darkening around the edges of the damaged area, but the deficiency does not cause the condition. If you suspect your soil is deficient in boron, send a sample in for a soil test.

Boron-deficient plant with hollow stem (UCANR)

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Preventing hollow stem

​While there’s nothing you can do about a sudden heat wave, there are many things you can do to prevent hollow stem from happening in the first place:

• Install plants at times when temperatures are cooler
• Choose varieties that are smaller, rather than fast-growing or giant varieties
• Plant resistant cultivars
• Avoid excessive nitrogen or potassium applications
• Space plants according to seed packet or plant label directions

Keep your brassicas healthy by allowing them to grow slowly and steadily.