By David Hardy and Dr Natasha de Vere
We are getting a bit closer to knowing which flowers honey bees like best, with the Garden’s Science Team’s latest results just published in the open access journal Scientific Reports.
We want to find out which plants honey bees prefer to help inform future choices when it comes to managing habitats and planting pollinator-friendly flowers. Understanding honey bee behaviour is crucial. Seventy-five per cent of food crops are dependent on animal pollination but, globally, we are facing a pollinator crisis due to a perfect storm of habitat loss, intensive agriculture, climate change, pests and disease. A big problem for honey bees is lack of suitable habitat for foraging brought about by the loss of hedgerows, woodland and meadows rich in plant species.
Spring is a crucial time for honey bees. Over winter, they will use up all their stores of honey. As winter progresses, they will start to produce brood and, as soon as the sun comes out in early spring, they need to gather nectar and pollen to replenish their stores. The protein from the pollen is used as food for the brood so it is vital that they have a wide variety of flowers available.
The Garden’s Science team set out to investigate which plants the honey bees used most during the spring. The results are very clear: there were 437 different genera of plants in flower in April and May in the Garden. But the honey bees only used 47 – or 11% – of these.
So, despite everything that was on offer, the honey bees only used a few plants and used them a lot. The Garden offers them a magnificent menu of more than 8,000 types of plants but the results show that they rely on hedgerow and woodland species such as willow, hawthorn, oak and dandelion for most of their diet. This is supplemented with a small number of garden plants including cotoneaster, hellebores and spring-flowering bulbs.
The research is part of the Garden’s ‘Saving Pollinators’ programme. It is achieved by DNA metabarcoding honey collected by the honey bees in the Garden’s hives each month. The Garden has eight beehives, which, during the summer, contain a quarter of a million bees.
By identifying plant DNA from pollen in the honey we can reveal which plants the honey bees have been visiting. This is only possible because the Garden has already DNA barcoded all of the native flowering plants of Wales as part of the Barcode Wales project.
There are pollen grains in the honey and the DNA is extracted from these, DNA barcode markers are amplified in the Garden’s labs and the DNA is sequenced at the Aberystwyth University Genomics Centre. The DNA sequences from the honey are then identified by comparing them to the Barcode Wales DNA reference library to find out which plants the honey bees have visited. The Garden’s wildlife conservation volunteers monitor what is in bloom at the time and this is compared with the plants found in the honey to see which plants the honey bees use compared to those that are available.
The main conclusion is that, during the spring, honey bees mostly use native hedgerow and woodland plants which means we must conserve these habitats. The results also show that honey bees are supplementing this main diet with smaller amounts from parks and gardens – proving what we do in our own backyard is crucial. A lack of suitable flowers means honey bees won’t have the healthy and diverse diet they need to withstand the other pressures they face, such as pests, disease and insecticides.
The plants the honey bees used most abundantly are nearly all native plants (and their relatives) mostly found in hedgerows and woodlands.
Top 10 spring flowers foraged by honey bees for nectar and pollen
- Willow (Salix species)
- Hawthorn (Crataegus monogyna)
- Cotoneaster (e.g Cotoneaster horizontalis)
- Apple and cherry trees (Malus and Prunus species)
- Gorse (Ulex europaeus)
- Sycamore and other Acer species
- Hellebores (Helleborus species)
- Dandelions (Taraxacum officinale)
- Holly (Ilex species)
- Oak (Quercus species)
At a lower level, they also used the following garden plants:
Top 10 garden plants
- Peonies (Paeonia species)
- Camassia bulbs (Camassia species)
- Grape hyacinth (Muscari species)
- Viburnum (Viburnum species)
- Wallflowers (Erisymum species)
- Ornamental alliums (Allium species)
- Skimmia (Skimmia japonica)
- Anemone (e.g. Anemone blanda)
- Roses (species with open flowers like Rosa canina)
- Flowering currant (Ribes sanguineum)
This picture will change, though. These results only relate to spring. Laura Jones is continuing the project as part of her PhD. She is investigating which plants honey bees use during the other seasons and how it varies from year to year. She is also inviting beekeepers to give samples of honey to find out the plants used by honey bees throughout Wales.
What can we do to help honey bees in our gardens during the spring?
The answer is: plant a willow, a hawthorn and some apple and cherry trees. Don’t pull up the dandelions in your garden and add in some of the supplementary flowers like the spring-flowering bulbs (camassia, muscari and alliums) and shrubs (viburnum, skimmia and open-flowered roses) to best support honey bees. If you are planting or managing hedgerows, make sure they contain the top honey bee favourites and make sure you allow them to flower.