Clover, belonging to the genus Trifolium, is a highly valuable forage crop and an excellent resource for pollinator conservation. The plant’s historical significance in agriculture establishes it as a consistent and widespread food source across many ecosystems. This legume is a foundational element supporting the nutritional needs of numerous insect species, particularly bees, throughout the foraging season. The ease of cultivation and widespread establishment of clover species contribute significantly to their positive role in supporting insect populations.
Resources Clover Provides
Clover flowers offer a dual contribution to pollinator nutrition by providing both energy-rich nectar and protein-heavy pollen. Nectar serves as the primary fuel source for adult insects, allowing them to power their flight and foraging activities. The pollen produced by clover is rich in protein, a nutrient essential for the development and growth of larval bees.
The flowers are densely clustered into a single head, providing an efficient foraging stop for insects and minimizing the energy spent traveling between individual florets. Clover maintains a relatively consistent nectar flow, which makes it a reliable food source during the peak foraging months of late spring and summer. This sustained availability is an important feature in environments where other floral resources may bloom and fade quickly.
Key Clover Species and Their Primary Users
The effectiveness of a specific clover species as a pollinator resource depends largely on the length of its floral tube and the tongue length of the visiting insect. Different clover types have evolved flower structures that favor certain pollinator groups, creating distinct foraging niches.
White Clover (Trifolium repens) is common in lawns and pastures, characterized by its short floral tubes. These accessible flowers are readily visited by generalist pollinators, including honeybees, smaller native solitary bees, and hoverflies. The short tubes allow these insects to easily reach the nectar reward.
Conversely, Red Clover (Trifolium pratense) has a longer, deeper floral tube, which restricts access to the nectar. This structure makes Red Clover a primary food source for long-tongued insects, most notably bumblebees. Bumblebees are equipped to effectively pollinate this species, as the tongues of generalist honeybees are often too short.
Crimson Clover (Trifolium incarnatum) is an annual species recognized by its striking, upright crimson flower heads that appear early in the season. Its early bloom period makes it an important resource for emerging insects, offering substantial nectar and pollen when other forage options are scarce. This species helps bridge the seasonal gap between spring and summer blooms.
Incorporating Clover into Landscapes
Cultivating clover in home landscapes is a practical way to support pollinator populations, often requiring less maintenance than traditional turfgrass. Overseeding an existing lawn with a micro-clover variety is a simple method, as the seeds can be broadcast directly onto the soil surface after the lawn is mowed short. Establishing a clover lawn or a mixed clover-grass sward creates a continuous food source for local bees and butterflies.
Maintenance practices must be modified to maximize the benefit for foraging insects. Avoiding the use of broadleaf herbicides is necessary, as these chemicals will eliminate the clover. Mowing habits should also be adjusted to preserve the floral resources.
Reducing the frequency of mowing allows the clover flowers to bloom fully and remain available to pollinators for longer periods. Alternatively, raising the mower deck height ensures that the clover heads are not completely removed during the mowing process. Clover thrives in full sun and well-drained soil, and its drought tolerance means it requires less supplemental watering than many turfgrass species.
Ecological Considerations
While many common clover species are not native to North America, they are now widely naturalized and provide an important component of the ecosystem. These non-native legumes often fill a significant gap in the foraging calendar, especially in highly developed or agricultural landscapes where native floral diversity has been diminished. Their presence offers a reliable food source throughout the summer months when native options may be sparse.
Clover’s inclusion in a landscape provides an indirect benefit through its ability to fix atmospheric nitrogen into the soil. In a symbiotic relationship with Rhizobium bacteria, the plants convert nitrogen gas into a plant-available form, which reduces the need for synthetic nitrogen fertilizers. A healthy clover stand can contribute between 100 to 200 pounds of nitrogen per acre annually, functioning as a natural soil amendment.
This nitrogen enrichment can improve the overall health of the soil and surrounding plants. However, the addition of nitrogen can favor the growth of other non-native species, sometimes leading to competition with native flowering plants that are adapted to nutrient-poor soils. Therefore, when introducing clover, it is important to consider a balanced approach that includes a diversity of native plants to ensure a robust and varied ecosystem.