Friday, 21 April 2017

Wildlife Gardening: Nectar Sources and Food Plants




Common Blue (Polyommatus icarus). Male (the females are brown).

B over at Coastal Ripples has penned a very interesting post on the results of Jersey's first ten years of butterfly monitoring on the island. It has nudged me to do a post about wildlife gardening, specifically about nectar sources and food plants. 

Although these sound the same, they are two different things. While filling your garden with wonderful plants that provide nectar for insects and pollinators is undoubtedly a good thing, unless you also provide the food plants in an area where they can lay their eggs and the young feed and grow undisturbed, you're only giving them half what they need to survive. 

Large Red-tailed bumblebee queen nectaring on apple blossom in our garden yesterday (Bombus lapidarius)

A lot of attention has rightly been given in recent years to encouraging people to provide nectar sources in their gardens but we also need to provide food plants and to be prepared for these food plants to be eaten and to look nibbled. This may go against the grain for many gardeners, but if we want to support the continued survival of our wildlife (and through them our own), we need to look after them properly and shift our aesthetics a little bit as a result.

Brown Argus (Aricia agestis). Female (the orange spots on the borders of the upper wing reach all the way to the top. In the male they stop half way).

A nectar source is a flower that the adult insect takes nectar from to convert into energy for their own survival. Things like penstemons, lithodora, scabious, ribes, apple blossom all provide nectar for insects. A food plant is one the adult insect lays its eggs on, and where the resulting larvae feed until big enough to pupate. Things like nettles, cuckoo flower, grasses are all food plants for different species. Food plants are more complex than nectar sources because they aren't universal. Often a species has a preferred food plant/s and won't lay their eggs on anything else. This is the case with butterflies and sawflies. Butterflies know which is the correct food plant to lay on because they have taste receptors on their feet. As soon as they land on something they know whether it's what they're looking for. In addition, some butterflies also have a preference for a certain colour of flower to nectar from. Marbled Whites for example seem to prefer purple or lilac plants.

Small Blue (Cupido minimus). Male. (note the stripy stockings!).

Some insects make nests in the ground that they fill with pollen to feed their young (bees do this), so for them a good nectar source is all they need. Others are parasites that lay their eggs in the nests of host species; the parasite larvae eats all the pollen left by the host species and ultimately eats the host's larvae too. A good example of the latter is the rather beautiful bee-fly, which is a parasite of andrena mining bee nests. They are on the wing now, so if you have small heaps of powdery soil in your lawn (which are the nests of the andrena bees) it's worth keeping an eye out for these amazing-looking insects nearby as the females will be egg-laying near the bee nests round about now.

Worth bearing in mind too that these creatures have evolved to live together this way. It may not be pleasant to us but it is how their life cycles work.

Dark-edged Bee-Fly (Bombylius major)

Another parasite species is Ephialtes manifestator, a type of ichneumon wasp. The long tail in the pic below is not a sting as some folks might at first sight assume. It's actually an ovipositor, used for laying eggs on or in the host species larvae, so this one is a female. They are parasites of solitary aculeates (bees, wasps and ants). I took this photo yesterday, so they are on the wing now and will remain so until September. Amazing creatures. Incidentally, ephialtes was an Athenian politician and an early leader of the democratic movement. I love the connections some species have!



Cuckoo bees, which lay their eggs in the nests of specific bumblebee species (the Field cuckoo bee is a parasite of the Common carder bee, while the Hill cuckoo bee lays its eggs in the Large red-tailed bumblebee nest) are different again, in that they don't spend as much time foraging for food as the other bumblebees because they don't need to provision a nest with supplies of pollen. For this reason, cuckoo bees don't have pollen baskets on their legs. For them, a reasonable nectar supply is enough.

Right, onto butterflies, who are a wee bit more choosey than the bees when it comes to food. In the UK we have a number of specialist species, one of whom (the Small Blue) is so specialist it only has one food plant associated with it, Kidney Vetch. This makes it prone to colony wipe out unless the habitat is preserved in a condition that allows kidney vetch to flourish. Another is the Purple Emperor: the adults feed on honeydew from aphids at the top of oak trees and the larvae hatch out, overwinter, feed and pupate on goat willow. Silver washed fritillaries are creatures of ancient woodland who lay their eggs on trees close to clumps of violet: the young hatch out, crawl down the trunks, feed on the violets, crawl back up the trunks and pupate on the trees. As most of us won't have Chalk or oaks or goat willow or violets growing under old trees in our gardens, we needn't worry about trying to get kidney vetch to grow or attracting Purple Emperors or silver washed Frits. They may pass through your garden of course (the Emperor in particular is noted for its fondness for dog poo). 

Clockwise from top left: Large Skipper (male), Silver Washed Fritillary (male), Ringlet, Marbled White

What we will have is the more generalist flutters, and those we can provide for. Here is a list of nectar source (NS) and food plants (FP) for the more common UK butterflies. Plant a few of each in your garden and they will love you for it. Remember with the grasses not to cut them back until the following spring, March/ April time.

Comma.
FP: nettles, hops, elm, currants, willow
NS: wide variety- buddleia, scabious etc

Peacock.
FP: common nettle
NS: buddleia, hemp agrimony, teasle as well as many others.

Small Tortoiseshell.
FP: Common nettle, small nettle, hop
NS: wide variety: cornflower, corn marigold, buddleia etc

Painted Lady.
FP: thistles
NS: wide variety: Daphne, scabious, nepeta, buddleia, jasmine etc

Red Admiral.
FP: common nettle
NS: wide variety as above

Large, Small & Essex Skippers
FP: areas of mixed grasses left long over winter, especially Cock's foot and Yorkshire fog.
NS: field scabious, red clover, bramble, red Campion, thistles

Small Copper:
FP: common and sheep's sorrel
NS: wide variety (daisies, dandelion, cornflower, scabious, bird's-foot trefoil)

Dark Green Fritillary
FP: violets
NS: knapweed, red clover, purple and mauve flowers

Common Blue
FP: bird's foot trefoil, white clover, black medick
NS: wide variety (bird's-foot trefoil, daisies etc)

Holly Blue
FP: Holly (1st brood early spring), ivy (2nd brood late summer)
NS: bramble, forget-me-nots, holly

Orange Tip
FP: lady's smock (also called cuckoo flower), garlic mustard, jack in the hedge, bittercress
NS: bugle, honesty, Daphne, scabious

Speckled Wood
FP: grasses
NS: aphid honeydew on oak, ash and birch

Gatekeeper
FP: grasses
NS: bramble, fleabane, ragworts

Meadow Brown
FP: grasses
NS: thistles and wide variety of meadow flowers

Ringlets
FP: grasses

NS: Bramble and others

You'll see that many of the plants they need for both nectar and food plants are what we call 'weeds', the sort of plants people work hard to eradicate from their gardens. One solution is to have a few wild patches dotted about where the insects can benefit from plants we don't always choose to grow, leaving space for people plants in other areas.

Other plants I've observed of particular value to pollinators as nectar sources in our garden here include:

Nepeta (covered in bees and flutters by day and by moths especially Silver Ys who've just flown in across the sea at night).
Fuchsia (especially for moths)
Willowherbs (food plant for elephant hawkmoths)
Scabious
Anemone
Penstemon
Bugle
Viper's Bugloss
Dandelion
Daisy
Echinacea
Antirrhinum
Buddleia
Star Jasmine
Cowslips
Salvia
Gaura
Lavender
Lithodora
Lungwort
Saxifrage
Ceonothus
Marjoram 
Poached egg plant
Bird's-foot trefoil
Clover
Astrantia
Borage
Ox-eye daisy

Hopefully that's given you some pointers. I'd love to know what you see in your garden as a result of putting some of this into practice this year. Even a few small changes make a significant difference to our wild cousins.

Hope you're all well,

CT :o)






12 comments:

  1. Really interesting post, I try and make our garden wildlife friendly, I choose only single flowers as I know bee's and insects can't get into double flowers. We have little areas for all types of wildlife, our garden is small, but we try to do what we can. I watched an interesting programme on TV, about a gardener who in the late 70's was wildlife gardening, which at the time was against all the feelings at the time as we were encouraged to get rid of wildlife. Our gardens are a much better place, always there is something to watch, from insects, butterflies, birds, a visiting hedgehog family, a family of field mice living underneath my butler sink filled with mints.

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  2. Thanks for the information, CT. I won't feel nearly as guilty about the crop of nettles growing behind my greenhouse now! xx

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  3. I have seen these bee flies I wondered what they are, interesting to see.x

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  4. A brilliant post, very informative. I was just telling the children about purple emperors and dog poo the other day - I remembered it from when you mentioned it once before and I thought it might be the sort of fact they would relish. Which of course it was. We have a buddleia here that just sprang up in the hedge. It doesn't flower but I've noticed that something eats the leaves quite a lot. Plenty of nettles here and down at the allotment too as well as holly, ivy, thistles, currant and grasses. Great to have a reminder about food source plants as well as nectar ones. CJ xx

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  5. Thank you for the mention. I have loved your post, full of great information. I have only been thinking about pollen sources not food plants so this has certainly put me straight. Will be looking at your great list for plant ideas. Spent the afternoon on the north coast cliffs. An amazing number of painted ladies going about the business. Have a great weekend. B x

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  6. Very informative and something we need to know at work for the garden I'm trying to set up

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  7. Beautiful images and very useful information!
    I love those stripy stockings - he's all ready to play football with a very small ball...
    Also like the bee fly.
    All the best :)

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  8. I really enjoyed reading this and the photographs are so beautiful. I has no idea about food plants. X

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  9. As always such a great post !
    I had to take out some of my rosemary plants and now I am very worried about my bees.
    More rosemary to be planted and I am designing some Arizona (solitary) Bee sculptures that are homes for them and art for me.

    cheers, parsnip

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  10. This was so interesting to read. A couple of years ago I planted some milkweed for our native monarch butterflies to lay eggs on. This is the only butterfly that I know about. I haven't noticed an increase in butterflies, but here's hoping that single milkweed plant will spread a bit each year. Thanks for your insight into all these insects.
    Wendy

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  11. Fascinating, CT. Thank you. We cut our wildflower patch back in late autumn but will now leave it until March! Another plant that's always covered in insects here is Verbena bonariensis. The absolute top plant in the past six weeks or so, though, has been pulmonaria (lungwort, as you've listed) - it's been covered in bees daily and it's so long-lasting. Sam x

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Thank you for leaving a comment. I always enjoy reading them and will try my best to reply to every one. CT x