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 autumn and the plant will continue flowering right into the new year.

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 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 resources for 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 worker gathering pollen

A bumblebee (B. terrestris) queen

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

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0009559

You can also submit your sightings of winter-active bumblebees to BWARS, the Bees, Wasps and Ants Recording Society:  http://www.bwars.com/index.php?q=content/winter-active-bombus-terrestris-data-gathering

 

A hoverfly enjoys the mild winter day

Hoverflies will visit mahonia flowers as well and you can also see bigger flies feasting on the nectar. And if it is getting cold again the flowers provide a convenient hiding place.

Milder winter days will also bring out honeybees which only forage if temperatures are above 10 °C.

A honeybee collecting nectar from mahonia flowers

Flies like to collect nectar from the flowers

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.