Hollow Heart

Sometimes things look fine on the outside when the inside is damaged. This can happen to people. And it happens in beets, potatoes, seeds, and watermelons.


If you cut a beet, potato, seed, or watermelon in half and find the empty space in the center, it has hollow heart. Also known as hallowheart, this condition indicates that the plant faced more stress than it could handle. [The same might be said for people, but I digress.]

Watermelon with early-stage hollow heart (utroja0) Pixabay

Sadly, this was the only licensable photo of hollow heart I could find.

Hollow heart of beets

If you cut into a beet and find an empty center, it’s time to get your soil tested. Hollow heart in beets is most commonly caused by a boron deficiency. If you look closely at the petioles, you will see that they are cracked, deformed, or smaller than normal. If the cavity is rotting, it may be black heart.


Hollow heart of potatoes

Hollow heart in potatoes is related to the water supply. And hollow heart is only one potato problem caused by irregular watering. Splitting and spraing (brown lines) are also water-related. Cold injury can also cause hollow heart in potatoes.

Potatoes are greedy plants. They need a lot of water and nutrients to produce those fat tubers. Hollow heart occurs when a developing potato is hit with a sudden dry spell, followed by an extended wet period. You know, that time you forgot to water them and then made extra sure they had plenty of water. That’s when it happens. This condition is a lot like blossom end rot in tomatoes. The lack of water causes deficiencies in immobile nutrients. [Did you know that tomatoes and potatoes are so closely related that you can graft the two together to get potatoes from underground and tomatoes above ground? It’s called a pomato.]


​​When hollow heart appears at the stem end of a tuber, it is usually caused by a cool weather start followed by a hot weather finish. Brown centers are commonly seen in stem end hollow heart. Hollow heart cavities found at the bud end usually do not have a brown center and are generally caused by nutrient- or water-stress later in the growing season. Small varieties are less likely to develop hollow heart than larger varieties. Russet Burbank and Yukon Gold are highly susceptible to hollow heart.

A pomato (sold as TomTato) in a store display. (Jonas Ingold) CC BY-SA 2.0

​Hollow heart in seeds

Garden peas and other seeds can also develop hollow heart. This occurs when unusually high temperatures occur right after germination begins. Because this disorder happens so early in the plants’ development, it leaves plants vulnerable to several fungal diseases. The best way to avoid hollow heart in peas and other seeds is to plant at the optimal time of year for each species.
 
Hallowheart of watermelons

Hollow heart in watermelons is mostly caused by insufficient pollen transfer. Poor pollination occurs when temperatures are low or when there are not enough pollinators in the area. Somehow, poor pollination causes the interior of a watermelon to develop triangular, often symmetrical gaps in the fruit. Seedless watermelons are more likely to develop hollow heart than seeded varieties, and orange and yellow-fleshed watermelons are the most likely to develop this condition. I have no idea why. What I do know is that you can attract more pollinators to your watermelon patch by adding flowers that appeal to both honey bees and bumblebees. You can offset low temperatures with row covers.
 

Hollow heart in watermelons can also occur when they are hit with too much fertilizer combined with not enough water, making the cells responsible for producing fruit unable to keep up with the cells producing rind.

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Bottom line: a steady supply of water, planting at the appropriate time, and the right amount of nutrients can help prevent hollow heart from occurring in your garden.