Adventitious growth on trees, commonly referred to as water sprouts and suckers, is a frequent sight that often causes concern. These fast-growing, upright shoots are a tree’s natural reaction to various stimuli, sometimes signaling a deeper issue within the plant’s health or environment. While they display vigorous growth, their presence is frequently detrimental to the long-term health and structural integrity of the tree. Understanding the origin and impact of these shoots is crucial for proper management.
Identification and Origin of Water Sprouts and Suckers
Water sprouts and suckers are both forms of adventitious growth, but they arise from distinct locations on the tree. Water sprouts, also known as epicormic shoots, emerge directly from the trunk or major branches. They develop from latent or dormant buds beneath the bark and typically grow straight up at a sharp angle to the parent branch.
Suckers, by contrast, originate from the root system or the base of the trunk, often below the graft union on cultivated trees. This root growth is a new, separate shoot that can appear several feet away from the main trunk. Both forms are characterized by their unusually vigorous, rapid growth rate compared to normal branch extension.
The appearance of these shoots is a biological mechanism for survival, initiated when the tree senses a need for replacement foliage. The buds from which they grow are usually held in check by plant hormones until an event triggers their sudden activation. Distinguishing their location is important for proper management, especially on grafted varieties where suckers will display the characteristics of the rootstock rather than the desired cultivar.
Triggers for Excessive Sprouting
The primary physiological reason for the proliferation of water sprouts is the loss of apical dominance, a hormonal control mechanism. Normally, the terminal bud at the tip of a branch produces auxins, hormones that suppress the growth of lateral and dormant buds. When a large portion of the canopy is removed, this hormonal signal is interrupted, causing a surge in growth hormones that stimulate the dormant buds into action.
Improper or excessive pruning is a frequent cause, especially when techniques like “topping” or heavy heading cuts are used. These methods remove a significant amount of the tree’s photosynthetic tissue at once. This drastic reduction forces the tree into panic growth, attempting to quickly restore its leaf surface area to produce energy. The intensity of this reactive growth is directly proportional to the amount of live wood removed.
Environmental stress is another major trigger, activating these emergency growth mechanisms. Conditions such as severe drought, sudden over-watering, root damage from construction, or soil compaction can stress the tree’s system. The tree interprets this stress as a threat and attempts to produce quick, new growth as a compensatory effort to regain vigor.
Impact on Tree Structure and Vigor
Water sprouts and suckers are generally considered undesirable because they divert energy from more beneficial parts of the tree, functioning as “sugar sinks.” They consume carbohydrates and nutrients the tree needs for developing stronger permanent branches, producing fruit, or storing energy in the roots. This drain on resources reduces the tree’s overall vitality and growth rate.
Structurally, these shoots are problematic because they are weakly attached to the parent branch or trunk. Unlike normal branches that develop a strong collar and wood structure, water sprouts originate from shallow, dormant buds and are prone to forming narrow, V-shaped crotches. These weak attachments are highly susceptible to splitting or breaking off under the load of wind, ice, or fruit.
Furthermore, the dense, rapid growth of water sprouts can severely crowd the interior canopy of the tree. This dense foliage reduces air circulation, which creates a humid microclimate that favors the development and spread of fungal diseases. Reduced light penetration also diminishes the health of interior leaves and can lead to shading out lower, beneficial branches.
Management and Prevention Strategies
The most effective management strategy for water sprouts and suckers is early and complete removal. These shoots should be pruned off when they are young and soft, as removing them while they are small minimizes the wound size and the energy lost by the tree. For water sprouts, the cut should be made flush with the parent branch or trunk, taking care not to leave a stub, which can encourage multiple new sprouts to form.
Suckers emerging from the roots or the ground must be severed completely at their point of origin, which may require carefully scraping away a small amount of soil. Simply tearing or mowing suckers off often stimulates the surrounding dormant buds on the root system to generate even more growth. The best time for removal is often during the dormant season, but prompt removal of new suckers is warranted at any time.
Long-term prevention focuses on addressing the underlying causes of the sprouting response. Maintaining optimal tree health through proper cultural practices is the most successful approach. This includes:
- Ensuring the tree receives consistent, adequate water, especially during periods of drought.
- Avoiding soil compaction.
- Using correct pruning techniques, such as making thinning cuts rather than heading cuts.
- Avoiding the removal of more than 25 to 30 percent of the canopy at one time.
These practices will significantly reduce the stimulus for adventitious growth.