
Are plants for pollinators enough?
Most advice for choosing plants to attract wildlife to your garden focuses on their ability to produce nectar. The RHS studies for their 'Plants for Pollinators' lists compared native and non-native plants according to how many species were found drinking from them and concluded that there was no qualitative difference between the two. This approach, though, doesn't tell the whole story. While most adult insects are happy to drink from any flower that's the right shape, their juvenile forms can be much fussier and will eat a much smaller range of leaves. The reason the Large Tortoiseshell butterfly is no longer common in the UK, for example, is not for a lack of flowers to drink from but because its caterpillar feeds on Elm leaves, a tree which is now largely absent after the terrible outbreak of Dutch Elm disease in the late 1960s. If we don't supply the food plants for the larvae we're not increasing wildlife numbers, we're just fighting between ourselves over the existing declining populations of adults.
Another reason I like to include native wild flowers where possible is that when cultivars are bred to be a different colour or have a larger flower they can lose some of the factors which make them appealing to insects. This can mean less nectar production, a difficult shape to drink from or simply a colour that insects ignore. One of the most interesting observations I’ve made is that, while honey bees will drink from almost anything, wild bees have definite colour preferences. Red and orange will be pretty much ignored in favour of colours that occur in UK meadows. They will drink from orange flowers when they stumble across them but, in the absence of fragrance, will be drawn most to yellows, whites, pinks, blues and lilacs.
(N.B. This doesn't mean that all modern cultivars are unhelpful but sorting out which ones have retained their value for wildlife is very much a process of trial and error. It's not always possible to go by the little bee stamp next to a plant on a website or label, as sellers won't necessarily do the observation needed, but will assume that because one, eg. Salvia, cultivar is attractive to pollinators, all are. Different retailers have different procedures, of course. If you wish to be sure, try looking at Rosybee.com, where they have done a six year study of a limited number of plants and have lots of useful information.)
Honeybees vs wild bees
The other distinction that the RHS doesn't make is between honeybees (Apis mellifera which are farmed, unfussy, and on the increase) and wild bees, which are dependent on habitat and in decline. Why do we need to care about wild bees? Well, for one thing, they are far more efficient pollinators. When honeybees collect pollen, they wet it with a bit of nectar and store it as a sticky paste in their pollen sacs. Wild bees just roll around in the pollen, loading up specially-designed patches of fur called pollen brushes. This means that when wild bees fly off home they scatter pollen around on the wind and over other flowers making them far more efficient pollinators than honeybees.
Native wild bees are also part of the UK ecology; they are individually adapted to drink from and pollinate a variety of different plants, depending on the length of their tongues. Bumble bees (and butterflies), for example, have long tongues and are particularly well adapted to deep-throated flowers, like some labiates. Honey bees only have medium length tongues, so will only go for flowers where the nectar is more easily accessed. In addition, the eggs of some wild bees provide the food source for individual species of predatory wasps. Who doesn't love to see a sparkling ruby-tailed wasp sunning themselves on the wall, or the fabulous stripy Sapyga quinquepunctata with its violet-tinted wings? Neither of these would survive if the wild bee species they depend on were to die out.
Pests and predators
Gardeners have probably perked up at the mention of predatory insects and yes, they're not just pretty to look at; they will eat the pests that are attacking your plants. This can be a slightly nerve-wracking way to run your garden. It requires iron will not to reach for the pesticide when you notice an infestation but bear with it, it does work.
Let me give you an example. I have a climbing rose, called Rosa 'Blush Noisette' which I would recommend to everyone. It flowers for months and months, from May until at least November, is extraordinarily healthy, fragrant, and provides a home for all kinds of insects. In spring, when it's just producing the first clusters of buds and tender, new leaves it becomes covered with aphids. It stays like that for long enough for me to consider throwing out my ecological credentials and unleashing chemical armageddon on them. As soon as the first hoverflies of the year pupate, though, they flit around laying eggs among the aphids, and when the larvae hatch they eat every single one of the little sap suckers. It happens so quickly that within a couple of weeks the rose is clean. The hoverfly I see most at this time of year is Epistrophe eligans, a shining bronze and black species that glitters like jewellery on the leaves. Later in the season, a host of tiny parasitic wasps no bigger than the aphids turn up and lay eggs in the aphids, turning them into a cocoon from which the new baby wasp will emerge.
Some pests and diseases are more successful than the predators that should be keeping them under control. I get a lot of Large Yellow Underwing caterpillars (Noctua pronuba) surfacing in my garden very early, before the predators are around to deal with them. These are also known as cutworms, and decimate the new shoots of some of my clematis. They're easy enough to pick off, should you wish, but the Ichneumonids turn up sooner or later to munch on them and it doesn't really matter if the Clematis gets set back by a few weeks. It gets there eventually.
Did you know that some species of ladybird eat mildew and scale insects? I didn't until relatively recently. Unfortunately I have a lot of mildew coming from a congested garden next door, and not nearly enough of these slightly rarer ladybirds to deal with it. My hope, though, is that if enough people put down the pesticides we will eventually get a better balance. One of the ladybirds I found eating the scale insects on my Trachelospermum turned out to be a very unusual species that was first discovered in 2014 in the grounds of the Natural History Museum (Rhyzobius forestieri) which was exciting.
The only caveat I would give is that if you are going to encourage the entire eco-system into your garden it does make sense to use the healthier varieties of plants. Little insect teeth (probosces, whatever) make tiny holes which can allow disease in if you have a particularly susceptible specimen. Plants naturally evolve to cope with such challenges but, just like nectar production, this resistance can sometimes be lost in the search for new colours and shapes.
How to grow native plants in your garden
It would be wonderful if all of us had enough room to make a dedicated wildlife area in our gardens. Somewhere, perhaps out of sight, that doesn’t matter if it gets straggly so we can still enjoy beautiful borders, have room for children to play, do our lockdown exercising, have a barbecue and enjoy a gin and tonic with a view, but we all know that in London that much space is unusual.
To this end I’ve been experimenting with growing native wildflowers among modern cultivars in my own small garden (which you can see above is a paltry 12m x 3m) to see which will perform well in a traditional setting. Unfortunately unless you have, say, an area of chalk downland behind your house, something you have admired in the wild will not perform the same way on nutrient-rich, soggy, clay-heavy, rubble-filled London soil. The trick is to find species which, while growing in a different way in captivity, will still hold their own in a flower border. Some, like Centaurea nigra (common knapweed), I’ve sadly had to give up on because, despite their obvious appeal to solitary bees, when they grow big from the excess nutrients they aren’t strong enough to stand up on their own. Staking just makes them into a slightly higher floppy mess.
Some, however, have been absolute stars – plants that I would now have in my garden even if I didn’t care about bees and butterflies. Here is a small selection:
Valeriana officinalis (common valerian)
Before you look away, this isn’t what most people think of as Valerian which is Centranthus ruber. Valeriana officinalis is a statuesque, multi-headed umbellifer growing to 2m tall with clouds of perfume reminiscent of vanilla and sugar. It starts flowering in late May and looks beautiful until July when the seed heads and stems turn pink. I usually cut it down after that to reduce self-seeding, but if you don’t plant them too close together (I did) they will stand up on their own for as long as you let them. In addition to a large variety of bees and hoverflies my Valerian supports lots and lots of ladybirds, shield bugs, butterflies, rose chafers (Cetonia aurata), and a very pretty black and white sawfly which lays eggs on Valerian (Macrophya albicincta.)
Scabiosa columbaria (small scabious)
More than a metre tall in suburban gardens, S. columbaria stays upright on thin, wiry stems, creating a cloud of bluey-lilac. This wildflower is hands down the plant that has attracted most pollinators to my garden. I reined it in a bit last year to make room for something else, and missed the extra buzz so much that I have put it all back again for this year. There are many Scabious cultivars on the market and this is the original wildflower from which many are bred. It starts flowering in July, and with a little judicious deadheading will keep it going until you're frankly ready to put the whole lot to bed for winter.
Origanum vulgare ( wild marjoram)
I’ll be honest here, Oregano seems to retain many of the qualities that are appealing to pollinators in its cultivars so sticking with the native wildflower isn’t quite as important as for other genuses. In fact I have 7 varieties of Origanum in my tiny garden, mostly in pots, but that’s just an unhealthy addiction. Oregano, mint and catmint (Nepeta), in addition to providing an abundance of nectar, attract lots of tiny, pretty mint moths (Pyrausta aurata). This can be a little annoying when you want a Mojito, but because they breed so successfully there are small caterpillars on the plants over a long period which seem to be particularly attractive to solitary wasps. I’ve always loved Ichneumons; those elegant, brightly-coloured, non-stinging insects and my mint moth caterpillars bring all the Ichneumonids to the yard, and plenty of Crabronids (digger wasps) and Ancistrocerus sp. too.
The wildflowers described here and more are always on sale at the NGS open garden at 105 Dulwich Village, London SE21. All images copyright the author.
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