An Evening with Hoverflies at the National Botanic Gardens Vegetable Patch

The vegetable garden at the National Botanic Gardens of Ireland is bursting with colour. Alongside their now fully organic array of heritage breed fruit and vegetables grows an abundance of flowers.

These blooms are not just pretty faces. They provide nectar and pollen forage for helpful insects such as parasitoid wasps, who will keep your cabbage caterpillar population in check, and some species of hoverfly*:, whose larvae are very effective aphid consumers.

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A happy population of hoverfly larvae can munch their way through 70-80 per cent of a greenfly infestation (Gardening Know How) and, as adults, will help to pollinate your garden plants. I’m getting to know these useful, cleverly disguised creatures at the moment, as I survey some pollinator-friendly sites for South Dublin County Council. Michael Viney, whose column was the only part of the Irish Times I read for my entire youth, is also a fan, and recently wrote an admiring tribute to the Marmalade hoverfly, Episyrphus balteatus.

Some flowering plants, such as nasturtiums, marigolds, borage, fennel, rosemary and chives, will also repel insects that you don’t want around your vegetables, such as carrot fly. These secrets of the national veg patch were revealed to me, my dad, and a large enthusiastic crowd of veggie food fans at An Evening with Cornucopia. Part of a series called Feasting from Nature’s Plate, the event featured Swedish chef Eddie Eriksson (surprisingly no Muppets references were made, though after reading this article I want to apologise to Eddie for even mentioning them here) and Organic Gardener Joan Rogers. A fascinating tour of the vegetable garden was followed by mouth watering demonstrations, salads, juices and dessert, and an astonishing amount was learnt!

I was particularly blown away by the tale of the Three Sisters – squash, corn and beans – who grow in community, depending on each other’s beneficial company. Native American farming societies interplant these three crops side by side in the same mound. The corn provides a support for the bean vines. The beans fix nitrogen in the soil and stabilise the corn in a strong wind. The leaves of the squash provide natural mulch to protect the roots and soil moisture. And at the end of the growing season, the left over plant matter can be dug into the soil as compost.

I am fascinated by these interactions and cooperations between species – corn and bean, human and plant, insect and dinner. I recommend planting some of your vegetable garden with some insect-friendly flowers so you can witness it for yourself.

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The National Biodiversity Data Centre’s recently published document Gardens – Actions to Help Pollinators contains advice on which plants best cater to the needs of insects:

  • Single instead of double flowered varieties: double flowered varieties provide almost no nectar and pollen for pollinators
  • Perennials over annuals: perennial plants are generally better sources of pollen and nectar
  • Do you see pollinators visiting it? When choosing plants to buy at a garden centre, you will quickly realise what flowers pollinators visit most. Also keep an eye out for the Royal Horticultural Society’s “Perfect for Pollinators” logo, which is now used by many suppliers of garden plants

Letting an area of your garden grow wild and seeing which wild flowers come up is also a great way to give nature what it needs.

While you wait for them to grow, a couple of events remain in the Botanic Gardens’ Feasting from Nature’s Plate series, and they are well worth attending!

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Another interesting feature of the Botanic Gardens’ vegetable patch: the blight-susceptible famine potato, with more modern potato breeds on either side.

*Edit: An original version of this post made a really clever pun out of the fact that some hoverflies are called drone flies. I’ve since been corrected – only Eristalis tenax can claim this name, and its larvae do not eat aphids. Plenty of others do though, so keep growing those flowers amongst your veg!

 

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