Whiptail

Whiptail is a disorder of broccoli and cauliflower.
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Growing cauliflower and broccoli takes time, space, and water. It can be frustrating to invest all that effort only to have the heads be inedible or nonexistent. Whiptail describes the way leaves of some plants become skinny. Heads may be small and ugly or not there at all. Luckily, whiptail is preventable.

Cauliflower leaves exhibiting whiptail next to healthy leaf (aaa) CC BY-SA 4.0

Whiptail symptoms

Stunting and severe chlorosis of leaf edges (margins) in young plants is the first symptom of whiptail. Those leaves may ultimately turn white. As the condition worsens, leaf blades do not develop properly, even though the midrib grows as it usually would. This creates a thin, strap-like shape to the leaves. Leaves may also cup upwards. The outer leaves may look perfectly normal, while the rest look like they have lost their leafy minds.

Instead of getting large, delicious heads, whiptail causes them to be smaller, malformed heads that taste less sweet. Or they may not grow at all. Whiptail symptoms are similar to manganese toxicity. Manganese toxicity appears as lightened leaves (interveinal chlorosis) with dark veins, leaf crinkling and puckering, dark spots on leaves, and stubby or absent buds.

What causes whiptail?

Whiptail is caused by molybdenum deficiencies in the soil. Molybdenum is a micronutrient used by specific enzymes. These enzymes have a laundry list of valuable jobs. Most importantly, they help make nitrogen and phosphorus available to plants. Legumes and the cabbage family use a lot of molybdenum, relatively speaking. When molybdenum is in short supply, those enzymes can’t do their jobs. Molybdenum deficiencies are common in acidic soils with a pH below 5.5.
            
Managing whiptail

Knowing what is in your soil is the first step toward preventing whiptail. The only way to really know is with an inexpensive lab-based soil test. Don’t be scared off by this. These tests cost about the same as a large bag of fertilizer, and the information they provide is invaluable. They will also tell you your soil’s pH. Once you know what’s in your soil, you can add any specific nutrients needed and work on getting rid of whatever may be present in excess.

Regularly adding organic matter to your soil will help prevent whiptail by improving soil health and adding easily accessible nutrients. If needed, adjust your soil’s pH. If your soil is too acidic, apply lime to “sweeten” it. Ammonium molybdate is often recommended but can be highly toxic and cause chemical burns. Personally, I wouldn’t want it anywhere near my edible plants. That’s just me.

Healthy purple cauliflower (Kate Russell)

If you see skinny leaves where they should be broad and abundant, take a closer look at what’s in your soil.