Sunflowers and bees

Few flowers attract life as visibly as a sunflower in full bloom. What from a distance looks like one large flower is in fact a densely populated head of hundreds of individual florets — and it is exactly that structure that makes the plant so attractive to pollinators. How that head is put together is covered under the anatomy of the flower head. This page is about what happens on it: who comes, why it helps the plant, and how you set up your garden or field so that bees genuinely benefit.

Nectar and pollen

A sunflower head offers pollinators two rewards at once. The disc florets at its centre — there can be hundreds to more than a thousand on a large head — do not all open at the same time, but in rings from the outside inwards, over several days. Each open floret supplies nectar as an energy source and pollen as a protein source. Because the bloom is spread over days, a single head stays attractive for a long time and a visiting bee need only fly briefly for a full load.

For a bee colony that supply is valuable, especially in late summer when many spring bloomers have already finished flowering. Sunflowers thus bridge a lean spell in the pollinator season. Timing that bloom in your garden is bound up with the sowing moment discussed in the growing guide.

Which bees

The visitors fall into two groups. Honeybees (Apis mellifera) often come in numbers and are the most conspicuous guests, certainly where there are hives nearby. But at least as important are the wild and solitary bees and bumblebees: in North America, where the sunflower comes from, there is even a group of specialised "sunflower bees" (genera such as Melissodes and Diadasia) that forage mainly on this crop. Research at the University of California, among others, shows that the presence of wild bees makes the work of honeybees more efficient, because the species influence each other's behaviour on the head (Greenleaf & Kremen, 2006).

In British and Dutch gardens you mostly see honeybees, buff-tailed bumblebees and various wild bee species on the head. That variety is a gain: a mix of pollinators delivers a fuller seed set than any single species alone. If you want to know which other plants and field margins sustain pollinators, that ties in with what happens on large sunflower fields.

Pollination and seed set

Here the bee story touches the grower's pocket. Most sunflowers are largely self-incompatible: pollen from the same plant rarely sets seed. There must therefore be transfer of pollen between plants, and that is done above all by bees. The more visits, the more florets are fertilised and the fuller the head fills with seed. Field studies, summarised by the FAO among others, consistently link more pollinator visits to a higher seed set and thus a higher yield in oilseed sunflowers (FAO 2018).

For anyone who wants the seed — whether for the press, for bird food or to eat — good pollination is therefore not a side issue but the basis of the harvest. The direct link between pollination and the full head you harvest later is covered in the harvest guide; what happens to that seed afterwards is under oil and seed.

Pollen as medicine

One of the most striking discoveries around this crop is that sunflower pollen not only feeds but also heals. Researchers Jonathan Giacomini, Rebecca Irwin and Lynn Adler found that bumblebees fed sunflower pollen had far lower infections of the gut parasite Crithidia bombi than bumblebees on other pollen — an effect that proved strong and repeatable in controlled experiments (Giacomini, Irwin, Adler et al., published in 2015). The pollen thus acts more or less as self-medication against a parasite that weakens bumblebees.

The effect seems to come from the physical and chemical properties of the pollen rather than from its nutritional value — sunflower pollen is itself rather low in protein. Later studies confirmed the parasite suppression, but qualified that a diet of sunflower pollen alone is too one-sided to keep bumblebees going. The message for the garden is therefore: sunflowers are a valuable addition to a varied flower supply, not the only course on the menu.

Which varieties do

Here lies the most important nuance of this page. Many modern cut-flower sunflowers are bred to be pollenless — they deliberately produce little or no pollen, so the flowers leave no yellow smears on the tablecloth and vase. Lovely for the vase, but for bees almost worthless: without pollen the protein reward is missing, and pollination largely falls away too. A field of pollenless florist varieties looks full of life but barely feeds a bee.

If you want to plant for bees, deliberately choose pollen-bearing varieties: old-fashioned perennials and large-seeded oilseed sunflowers supply pollen in abundance. A classic giant such as the Russian Mammoth is a reliable choice. On the seed packet or in the cultivar database you can often check whether a variety is pollenless; if it says "pollenless" or "pollen-free", give it a miss when pollinators are your aim. For a broader overview of varieties, see the species overview.

Planting for bees

A few choices make the difference between a garden that looks bee-friendly and one that really is. Choose pollen-bearing varieties, and plant not one but several sunflowers together so that bees can carry pollen between plants — that immediately helps seed set. Spread the bloom by sowing at different times, so there is food for longer. Leave faded heads standing: they supply pollen first and later seed for birds, as described in the harvest guide.

Avoid pesticides during flowering, because they hit exactly the pollinators you want to attract. And combine sunflowers with other forage plants, so that bees have a varied diet rather than the one-sided sunflower pollen alone. If you want to get going with children on this — sowing, counting which visitors come by — you will find fun experiments and facts on the kids' page.

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