Mahonia: a magnificent magnet for winter-active pollinators

There are not many flowers to be found at this time of year. You will probably spot some flowers of winter jasmine (Jasminum nudiflorum) and winter-flowering Viburnum species scattered around the gardens, but what is really standing out are the bright yellow scented flowers of winter-flowering mahonia.

Mahonia is often present in low-maintenance plantings together with other shrubs around buildings and in parks and easy to spot as it is often the only bright colour around at this time of year. Some people  have it planted in their garden but especially the tall mahonias such as Mahonia x media need quite a lot of space so not an option if you only garden in a small space.

The bright yellow racemes of Mahonia x media

There are several species of mahonia which flower in winter such as Mahonia japonica, Mahonia oiwakensis ssp. lomariifolia and Mahonia aquifolium (starts flowering in late winter) but the most commonly planted mahonia is probably Mahonia x media (a hybrid between Mahonia oiwakensis ssp. lomariifolia and Mahonia japonica) with its large, glossy leaves and bright yellow racemes. The flowers of Mahonia x media start to open in November and the plant will continue flowering until February.

It is not only us who are drawn to the flowers; they are also very attractive for winter-active pollinators as the flowers produce quite a lot of nectar. Have a closer look and you will be surprised at the pollinators you can see visiting the flowers on milder days in the middle of winter. 

Mahonia flowers produce a lot of nectar

The most obvious flower visitors are bumblebees of the species Bombus terrestris (Buff-tailed bumblebee) which can maintain winter colonies in urban and suburban habitats in the south of England. Beside strawberry tree (Arbutus unedo), winter-flowering heather and some other winter-flowering plants, winter-flowering mahonias are one of the most important food sources for the winter-active bumblebee Bombus terrestris and up to 75% of winter flower visitations are to mahonia flowers.

In the majority of cases you will see the bumblebee workers, busily collecting nectar and sometimes also pollen. They can fly in temperatures close to 0 °C and on overcast days and I have also seen them flying at dusk. If you are lucky you may sometimes spot a bumblebee queen which is markedly bigger than the workers. 

 

A buff-tailed bumblebee (Bombus terrestris) queen

A worker collecting pollen

Bumblebee queens are a lot bigger than worker bees

If you want to read more about winter-active bumblebees in the UK have a look at this interesting research paper.

You can also submit your sightings of winter-active bumblebees to BWARS, the Bees, Wasps and Ants Recording Society.

 

Other pollinators visiting mahonia flowers are different species of hoverflies such as from the genus Eristalis as well as other flies such as green bottles and flesh flies. The flowers also provide a convenient hiding place to survive cold nights.

Milder winter days will bring out honeybees which only forage if temperatures are around or above 10 °C. In late autumn and early winter you can also see the last wasps drinking nectar from the flowers. But don`t be afraid, they are more interested in the nectar than in you.

A wasp drinking nectar from the flowers

Two wasps meeting each other

Eristalis tenax is a common hoverfly in autumn

Common carder bees (Bombus pascuorum) are still around in late autumn

Honeybees only forage for nectar and pollen on milder days

A honeybee approaching a mahonia flower

Mahonia flowers provide lots of nectar for hungry hoverflies

A wasp searching for an open flower

Flies like to drink nectar from the flowers as well

A convenient hiding place for a fly

So next time you pass by some flowering mahonia bushes have a closer look, maybe you can spot some busy bumblebees or other pollinators flying around the flowers.

For more pollinator-friendly winter flowers have a look here.