The problem with lists, such as the RHS Perfect for Pollinators plant list, is the inbuilt assumption that if a plant isn't on the list, it's no good for insects. That's patently not true.
Nectaroscordum siculum does not appear on the list I have in front of me, but earlier this year, they were top favourites with the bumblebees in the garden. Each hanging bell was filled with a fat furry bumblebee bottom and the tall heads of flower beamed out an extraordinary high-pitched whirring, focused, industrious. Fortunately the stems of nectaroscordum, though tall, are very strong. When they were supporting the bumblebee tribe, they were carrying more than twice their normal load.
More lastingly useful than a list would have been to focus on and establish a few basic guidelines. Single flowers are better for pollinating insects than double ones. Flowers with heads made up of masses of tiny individual florets are most useful of all. Trials have shown quite conclusively that pollinating insects do not reject "foreign" plants in favour of native ones, and that, not surprisingly, pollinating insects have their own clear favourites. Some will go for lavender. Others favour bugloss. Colour matters too. Bees apparently like yellow and white flowers. Butterflies go for shades of red, pink and purple.
On the old sunken track that leads up the hill away from our house, clouds of gatekeeper butterflies were weaving in and around the hedges on either side earlier this month. At first I thought the attraction must be the old man's beard (Clematis vitalba) that rambles all over these particular hedges. But when I got closer, I could see that the greenish-white flowers weren't yet quite open. The draw was the wild marjoram (Origanum vulgare), that grows in great swathes on the banks under the hedge. Both plants bloom from July to September and the marjoram in particular with its clustered purple flowerheads provides a long foraging season for flying insects.
Marjoram is an easy plant to establish in the garden, as it doesn't mind poor soil. It likes sun though, as was obvious from the marjoram on the track where it grew only on the south-facing bank. Unfortunately the golden-leaved version, Origanum vulgare 'Aureum' burns in full sun and you have to give it some shade. But then it won't attract so many butterflies. Down here in our part of Dorset, where there has been only one night's rain since the beginning of June, there's no doubt that the crowds of butterflies in the garden are here because of the weather, not because I've been doing anything special to bring them in.
Nevertheless, there are plants which always seem to be covered in insects, especially annuals such as Ammi majus and Ammi visnaga. I had an unusually early display of A. majus because these were all self-seeded plants. They were already well-established by last autumn. Because it has been such an extraordinary growing season and because they had this head start, the plants got up to 4m/12ft tall, with more than 50 flat white heads of flower on each plant. They've almost finished flowering now, after a three-month season, overlapping with the A. visnaga which is just coming into bloom. Continuity of supply is what insects need and this flat-headed tribe of flowers, the umbellifers, are not just great garden plants, but provide plenty> of nectar and pollen. Flying insects need both: nectar for carbohydrate, pollen for protein.
Dill, which I wrote about last month is another member of the umbellifer family, as welcome to pollinating insects as it is in the kitchen. So is ridolfia, which I grew this year for the first time. Neither of the ammis, nor dill, nor ridolfia are on the RHS pollinators list, but I can vouch for them all as magnets for flying insects. The ridolfia, sown last autumn in mid-September has been spectacular. Height 1m/38in said the seed packet, so I planned to interplant it with deep blue larkspur, which is much the same height (the ridolfia has flat fennel-like heads of a very intense acid yellow).
I raised plants in individual 8cm/3in pots and planted them out in March this year. When they started to flower, they were already 4m/12ft high, wonderful airy explosions of the sharpest yellow you can imagine in wide flat heads of flower. The whole thing is lighter-limbed than fennel, the foliage fine and feathery, pale green with none of the dark tones that fennel has. As the summer progressed the stems became like bamboo canes, bleached cream, dry, hollow but fortunately very strong. Way up above the rest of the border these gorgeous clouds have been swaying. Or crashing. There's nothing in between these two states. When the wind really blew, the ridolfias did not have enough root to keep themselves upright. But the insects have loved them and I will certainly grow them again. I think though that next time, I'll sow seed in spring, which will restrict the size of the plants and bring them down to the level of the rest of the border. Of course, I could have staked them…. That's one of the many jobs that never gets done.
FOUR SUMMER PLANTS FOR POLLINATORS
Wild teasel (Dipsacus fullonum)
Tall, handsome native, biennial in habit. In July a band of pale purple flowers opens around the middle of each oval head, gradually spreading over the whole thing. Good for both bees and butterflies.
Perennial sweet pea (Lathyrus latifolius)
A perennial version of the annual sweet pea, though unfortunately without its scent. Available in white as well as various shades of pink. Popular with both bees and butterflies.
Fennel (Foeniculum vulgare)
A great attraction for hoverflies, which we tend to lump together under a single name. In fact there are 250 different species in Britain, many of them with an insatiable appetite for aphids. Hurrah!
Musk mallow (Malva moschata)
A favourite with honeybees, together with the common mallow (Malva sylvestris). Both flower between June and September with wide flowers in an easy shade of pale pink.
For a useful list of pollinator-friendly plants for town gardens go to the website of the London Beekeepers' Association (lbka.org.uk).
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