If you’ve ever been fruit picking or shopping, you’ve probably encountered a double fruit or two. While most people probably discard these items or judge them as unfit for consumption, it’s quite common to encounter them.
Fruit twinning, technically termed fruit doubling, is encountered in many fruits including apples, pears, peaches, cherries, and plums. Even quadruple fruit may be observed in peach and sweet cherry.
As illustrated in the photos, this phenomenon is characterized by two or more joined fruits emerging from a single stem. The photo below is an unusual example where the stem itself has split. Doubles—or conjoined fruit—are not an uncommon occurrence, however. Some varieties seem particularly prone to it, and have often one larger piece of fruit dominating the other.
This situation doesn’t always have a good outcome! In many cases, one of the pieces of fruit ends up so small as to really be unusable. You can see that in the example below. Or, the skin is torn when separating the two fruits, which of course downgrades the quality of the fruit during consumption.
Sometimes, though, the extra piece of fruit is so small as to be insignificant and may be removed without damaging the main fruit.
What causes Doubling?
Doubling is due to stress during the flower and bud development stage. Whether a fruit will be doubled or not is determined the summer previous to fruiting when the flower buds are going through their initial development.
As young growing buds are extremely sensitive to heat and water during this stage, water stress alters tree growth and causes an increase in the occurrence of doubled fruit.
If stress conditions are encountered during the flower bud formation, the cells that will ultimately form the fruit are partially separated from each other, and then each cluster of cells proceeds to develop as though it were the only. The trick is that these clusters are ultimately still attached at some point toward the upper end of the carpels. This results in two (or more) carpels within a single flower.
PS: Doubling of two large-seeded peaches or apricots is possible in the case of the pollination and fertilization of two present pistils.
When are Fruits the Most Susceptible to stress influence?
In most areas, fruits appear to be susceptible to fruit doubling from stress from early August to early September.
How does one avoid or minimize fruit doubling?
There’s not much you can do about heat waves, particularly with climate change affecting our environment so quickly. But you can make sure your trees get enough water (especially during a heat wave) to minimize the stress on the tree. Irregular or inadequate watering can also be one of the causes of fruit splitting, which is another whole story but can look like this.
In a home garden, it’s not terribly important whether you have double fruit or not because it’s usually still usable.