Crabapple trees (Malus genus) produce small, often ornamental fruits. The shedding of these fruits, known as abscission, is a natural biological process where the tree severs the connection between the fruit and the branch. Understanding the timing of this fruit drop is key for homeowners and gardeners. This process is influenced by the tree’s internal biology and external environment.
General Timeline for Fruit Drop
The fruit drop process begins with an initial, smaller drop of immature fruit, commonly called the “June Drop.” This thinning occurs in late spring or early summer, typically around May or June. The tree naturally aborts fruitlets that are unpollinated, damaged, or too numerous for the tree to sustain. This early drop is a healthy sign of self-regulation and results in small, pea-sized fruits on the ground.
The main fruit drop, involving mature fruit, generally begins in late summer and continues through early fall. For cultivars bred to shed their fruit, this period is often late September or early October. The fruit is fully ripened at this point, and the tree forms an abscission zone at the base of the fruit stem, causing the fruit to fall.
Some crabapple varieties are specifically cultivated to retain their fruit long past maturity. Fruit-retention cultivars, such as ‘Red Jewel’ or ‘Sugar Tyme,’ may hold fruit well into winter, sometimes until March or April. The drop is delayed until the fruit has been repeatedly frozen and thawed, or until birds and other animals consume it.
Variables That Affect Drop Timing
The exact timing of fruit drop is highly variable, depending heavily on the specific genetic makeup of the tree. Cultivars are broadly categorized as fruit-abscission types, which shed fruit in the fall, or fruit-retention types, which hold fruit for winter display. This genetic programming is the most significant factor determining whether the fruit drops in September or persists through March.
Environmental stress can override a tree’s natural schedule and trigger premature abscission. Prolonged periods of drought and high heat cause a stress response in the tree. To conserve moisture and energy, the tree initiates the separation layer at the base of the fruit, leading to premature fruit drop.
Pest pressure and disease also influence when fruit drops. Fungal infections, particularly apple scab, cause premature defoliation and fruit shedding. Heavy infection can cause the fruit to drop prematurely in mid-to-late summer, before it has fully ripened. Insect pests like the apple maggot can also damage the developing fruit, causing it to spoil and fall early.
Post-Drop Management and Cleanup
Once fruit has fallen, prompt and regular cleanup is necessary to prevent the dropped crabapples from becoming a source of pest and disease inoculum for the following season. Fallen fruit can harbor the overwintering stages of pests like the apple maggot, which tunnels into the fruit. It also provides a breeding ground for fungal diseases like apple scab and cedar-apple rust.
Allowing fruit to remain on the ground creates an environment for the disease cycle to continue. The decomposing fruit also attracts scavenging insects, such as yellow jackets and fruit flies, which can become a nuisance. Raking or sweeping up the fallen fruit every few days is the most effective cleanup method.
In terms of disposal, experts advise against adding fallen, potentially diseased fruit to a home compost pile. The fungal spores and pest larvae within the fruit require a high, sustained temperature to be killed, which is often not achieved in standard backyard composting systems. Instead, the fruit should be bagged and removed with household waste or buried deeply away from the tree to prevent the pathogens from completing their life cycle.