Companion planting involves growing plants together for mutual benefit. While some plants offer benefits to grapevines, others can negatively impact their health and productivity. Understanding these negative interactions is important for successful grape cultivation and a fruitful harvest.
Why Certain Plants Harm Grapes
Certain plants can negatively affect grapevines through various mechanisms, primarily resource competition, allelopathy, and by acting as vectors for diseases and pests. Grapevines, especially when young, require ample access to water, nutrients, and sunlight to establish strong root systems and healthy growth. Aggressive neighboring plants can outcompete grapes for these essential resources, leading to stunted development and reduced vigor. Weeds, for instance, are known to significantly diminish grape yield and quality by competing for water and nutrients.
Allelopathy is another mechanism where plants release biochemicals that can inhibit the growth of nearby plants. These natural chemicals, sometimes present in roots, leaves, or seeds, can be released into the soil and suppress the germination or growth of other species. Certain weed species produce allelopathic chemicals that directly reduce a vine’s growth and development.
Some plants can also harbor diseases or attract pests that are harmful to grapevines, acting as alternative hosts or intermediaries. Weeds, in particular, can serve as alternate hosts for disease pathogens, nematodes, and insects that also affect grapes. This can introduce and spread issues that might otherwise be less prevalent in a vineyard.
Plants to Avoid Near Grapes
Several specific plants are considered poor companions for grapevines due to the negative interactions they create. Fast-growing and nutrient-hungry plants, particularly certain vegetables, can directly compete with grapes for essential resources. Vegetables like lettuce, onions, and collard greens have high nutritional requirements and can outcompete grapevines, particularly for moisture and nutrients. Cabbage, in particular, is a heavy feeder that can leave less for grapevines to grow strong and healthy.
Fennel is known for its allelopathic properties, releasing chemicals that can inhibit the growth of many other plants, making it a generally poor companion in most gardens. While not specifically studied for grapes in all contexts, its broad allelopathic effect suggests it should be kept away from grapevines. Radishes are another plant that can compete with grapes for space and nutrients due to their rapid growth and shallow roots, potentially interfering with the deeper root systems of grapevines.
Beyond direct competition, some plants can host pests or diseases detrimental to grapes. While brassicas like cabbage and broccoli are sometimes mentioned, certain brassica cover crops can actually suppress the growth of bacteria, fungi, nematodes, and insect pests. However, general weeds, especially those with vine-like growth such as field bindweed or morningglory, can physically damage grape plants by climbing and strangling them. Weeds can also provide habitat for rodents that damage roots and trunks.
Addressing Problematic Plantings
If undesirable plants are already present near grapevines, taking corrective action is important to protect vine health. Carefully removing competing or harmful plants is crucial, especially during the early stages of grapevine establishment when competition is most impactful. Weeds are particularly competitive with newly planted vines, and their removal can significantly improve vine growth and yield.
Physical barriers can also be employed to prevent root competition and suppress weed growth. Using mulches can conserve soil moisture, suppress weeds, and increase soil organic matter. Plastic mulches can also be effective in controlling weeds.
Regular monitoring for pests or diseases linked to specific companion plants is an important management strategy. If issues arise, appropriate management should be implemented. Maintaining a weed-free zone around grapevines is recommended to minimize competition and reduce potential pest and disease harboring.
Proactive Grape Planning
Effective planning before planting grapevines can prevent many issues associated with bad companion plants. Site selection is a primary consideration, emphasizing an area free from existing problematic plants. Removing all trees and woody vegetation from the site before planting is advised to reduce shading and competition.
Proper soil preparation provides a strong foundation for grapevines. This involves ensuring good drainage and adjusting soil pH if necessary, as grapes thrive in well-drained, deep soil with a pH between 6.0 and 7.0. Soil testing prior to planting allows for the correction of nutrient deficiencies and pH imbalances.
Adequate spacing between grapevines and other plants is also important to minimize competition for resources as the vines mature. Each grapevine typically needs about 6 feet of space. Thorough research into both beneficial and detrimental companion plants before planting is also important.