Marigolds, belonging to the Tagetes genus, are popular annual flowers grown globally. These brightly colored flowers are often touted as excellent additions for attracting beneficial insects. However, whether all marigolds are equally effective at attracting and supporting pollinators has a nuanced answer that depends heavily on the flower’s physical structure. The efficacy of a marigold as a pollinator magnet is determined primarily by its bloom type.
The Critical Difference: Single vs. Double Blooms
The physical structure of a marigold flower is the most important factor determining its value to a pollinator. Marigolds are generally categorized into single-bloom and double-bloom types. Single-flowered marigolds possess a simple, open center that fully exposes the reproductive parts of the flower, known as the disk florets. This open structure grants easy access to the nectar and the pollen-rich anthers.
In contrast, double-flowered marigolds, often bred for their dense, pom-pom appearance, have undergone a genetic transformation. This breeding causes the flower’s stamens, which are the pollen-producing organs, to mutate into extra petals. The resulting voluminous layers physically block the entrance to the flower’s center, making the nectar and pollen inaccessible to most bees and butterflies. For example, the large African marigolds (Tagetes erecta) are primarily double-blooms that offer little nutritional reward.
Top Marigold Varieties for Nectar and Pollen
To maximize pollinator activity, focus on varieties that maintain the natural, open flower structure.
Signet Marigolds
Signet Marigolds (Tagetes tenuifolia), such as the ‘Lemon Gem’ or ‘Starfire’ series, are highly recommended because they naturally produce small, single flowers with fully exposed centers. These dainty blooms provide a steady supply of accessible pollen and nectar, making them excellent food sources for smaller solitary bees and hoverflies.
French Marigolds
Many French Marigolds (Tagetes patula) are effective, especially single or semi-double varieties like ‘Naughty Marietta’ or ‘Durango Bee’. These varieties often feature a central cushion of disk florets surrounded by a single ring of ray petals, offering a clear target for insects.
Mexican Mint Marigold
Another highly effective choice is the Mexican Mint Marigold (Tagetes lucida), known for its bright yellow, daisy-like flowers. It is particularly rich in nectar and attracts hummingbirds in addition to bees and butterflies.
Optimizing Your Garden for Marigold Pollinators
Selecting the correct marigold variety is only the first step; maximizing their benefit requires strategic planting and simple care practices. Pollinators are more likely to be drawn to a large, concentrated patch of color than to scattered individual plants. Planting marigolds in large groupings, often called “drifts,” creates a strong visual signal that increases foraging efficiency for bees.
Ensuring a continuous food source throughout the season requires regular deadheading, or removing spent flowers. This simple task encourages the plant to produce new blooms instead of diverting energy into seed production, guaranteeing a sustained supply of pollen and nectar. Gardeners must strictly avoid using systemic pesticides, which contaminate the pollen and nectar, posing a threat to any visiting insect. Proper placement in a location that receives full sun will promote vigorous growth and maximum flower production.
Beyond Pollination: Marigolds as Garden Helpers
Marigolds are valued for more than just attracting beneficial insects, offering a range of other positive effects in the garden ecosystem. They are widely known for their ability to manage plant-parasitic nematodes, particularly the destructive root-knot nematodes (Meloidogyne spp.). When grown as a cover crop, the roots of certain marigolds, especially French varieties, release a compound called alpha-terthienyl, which is toxic to these microscopic soil worms.
The aromatic foliage of marigolds also functions as a natural deterrent against certain insect pests, including whiteflies and aphids, leading to their inclusion in companion planting schemes. French marigolds can attract beneficial predatory insects like hoverflies, whose larvae are voracious consumers of aphids. By providing a nectar and pollen source for these natural enemies, marigolds help to maintain a healthier, more balanced garden environment.