Ecologist Ken Thompson explores how plants with bad reputations can actually be beneficial for your garden and for wildlife.
We can argue about the definition of a weed, but part of it is surely a plant’s ability to make itself thoroughly, immovably at home, often despite your best efforts to persuade it to go away. Among native plants, there can hardly be a better illustration of this than ivy.
The pesky plants we need to start liking
Ivy
If you don’t like ivy, the bad news is that it’s also one of the main beneficiaries of climate change. As an evergreen climber of mostly subtropical affinities, ivy was never very fond of cold winters. But now that such things are increasingly rare, ivy is able to grow almost all year round in warmer parts of the country. In fact, right across Europe, ivy is now more abundant where it grows, and grows in more places, and climate change is certainly to blame.
And yet, despite a reputation as something of an unwelcome thug, it’s hard to imagine a plant that’s more valuable to wildlife throughout the year. In autumn, ivy provides the year’s last great nectar harvest. Ivy is so widespread that bees generally don’t need to go far from the hive to find it, and studies show that honeybees travel about half as far in September to find food as they do in the summer. In fact, hives with plenty of ivy around are more likely to survive the winter. Honeybees also need pollen to raise their young, and hives that end the year with healthy pollen stocks can get going faster in the spring. Most of that late pollen comes from ivy.
In autumn, ivy provides the year’s last great nectar harvest
Ivy flowers are too late for most bumblebees, but they’re also visited by wasps (wasps are wildlife too) and by late-flying hoverflies and butterflies – a sunny patch of flowering ivy can be a magnet for red admirals and small tortoiseshells. Ivy also now has its very own bee: Colletes hederae (ivy bee) is a solitary mining bee that was first recorded in Dorset in 2001 and has now spread as far north as Cumbria and County Durham.
An ivy-covered wall, fence or shed provides winter shelter for no end of wildlife, including spiders, ladybirds and lacewings, and perhaps one or two of that hardy band of butterflies that overwinter as adults: red admiral, brimstone, comma, peacock and small tortoiseshell.
Fat-rich ivy berries are a vital winter food for blackbirds and thrushes, and in spring and summer, ivy provides ideal nesting habitat for many birds, including wrens, dunnocks and finches. Dense evergreens such as ivy are particularly useful for birds that want to make an early start on breeding and don’t want to wait for deciduous trees and shrubs to come into leaf.
Ivy is also one of the two food plants of one of our most common and most charming garden butterflies, the holly blue. In fact, there’s almost no end to the things that ivy can do for wildlife, especially if you stop persecuting it for long enough for it to grow up into the sun and flower.
Leyland cypress
When the Monterey cypress and the Nootka cypress, both from North America, accidentally crossed in 1888 to give us Leyland cypress, I doubt anyone realised the trouble it was going to cause. In fact, there’s nothing wrong with Leyland cypress also called leylandii – it’s a handsome, large (indeed potentially enormous) tree. The fault lies with people thinking it would make a good hedge, which it doesn’t – it’s too fast growing and too big. In fact, no one knows how big – the largest trees are now around 40m tall and still growing.
Leylandii provides good, dense evergreen cover – useful for birds to roost in over winter and nest in during the spring
But hardly any plant is completely useless, and even Leyland cypress has its uses for wildlife. Rather like ivy, it provides good, dense evergreen cover – useful for birds to roost in over winter and nest in during the spring. It’s also one of the reasons, along with the expansion of coniferous forestry, for the remarkable expansion of conifer-feeding moths in recent decades. Many British moths are declining, but species such as Blair’s shoulder-knot, spruce carpet, juniper carpet and pine beauty are all expanding rapidly. The biggest winner over the past ten years has been the cypress carpet, a new colonist moth from Europe that has spread rapidly after first being found in West Sussex in 1984.
Red valerian
Say what you like about Leyland cypress, it’s a sterile hybrid so at least it stays where it’s put, which is more than can be said for many garden plants. I’m not sure which is the most relentlessly persistent self-seeder in my garden, but red valerian (Centranthus ruber) is certainly a candidate. Which at least means that if you want to grow it, it’s just a question of waiting and it’s sure to turn up, probably sooner rather than later. You certainly shouldn’t need to buy it, although I’m astonished how often I see it for sale.
The long-spurred flowers of red valerian are favourites of the hummingbird hawk moth
But the long-spurred red, pink or white flowers of red valerian are the favourites of one of our most charismatic garden insects: the hummingbird hawk moth. This day-flying hawk moth is a summer visitor to the UK from southern Europe, sometimes in large numbers. It’s such a lovely animal that I think it’s a good enough reason on its own to grow red valerian, even if these plants will then repay your kindness by trying to take over your garden.
Read Ken Thompson’s piece on how AI might affect the way we garden