Tim EntwisleEvening primrose – confusing & mixed up

Our evening primroses are fading now, after weeks of adding a dash of pale canary yellow to our backyard here at Kew Gardens. Like all Evening Primrose they open on dull days (like today) and in the evenings, to be pollinated by hawk moths (with their famously long ‘tongues’) and other night insects.

We have a common weedy species of Oenothera, but which one? The Entwisle plants carry large flowers, about three inches across, and no red veins on the leaves or sepals (sepals being the outer bits of the flower – often, as in this case, the green bits). The stems do redden up occasionally and there is a hint of pink on the edges of the sepals.

It was here last year so I’m going to call it an herbaceous biennial. Oenothera biennis (the Common Evening-primrose), then, sounds good. However that species has flowers only two inches across at most. There is Oenothera glazioviana with bigger flowers, about the size of ours, but with red sepals. Like another not dissimilar species, Oenothera cambrica (with smaller flowers), its fruits have red hairs with swollen bases. Our fruit hairs are swollen at the base but definitely not red.

So it has bits of various species, suggesting it may be a hybrid or cultivar. There are some nice pictures on the Irish Wildflower site for Oenothera biennis which match ours beautifully, but they carry warning: ‘Photographs are not of Common Evening-primrose, probably of a hybrid’.

As always, Tony Cope’s The Wild Flora of Kew Gardens: a Cumulative Checklist from 1759 is helpful. He mentions a hybrid called Oenothera fallax, a cross between Oenothera biennis and Oenothera glazioviana. This hybrid has been recorded from a ‘neglected flowerbed in Lower Nursery’ which describes bits of our garden before we arrived, and certainly the meadow-like expanse next door.

Tony Cope says this hybrid may have escaped from cultivation or have arisen on site through hybridisation of its parents which he says are rare escapes from gardens. He gives it the common name of Intermediate Evening-primrose.

And then in the mail this week comes the latest issue of the Royal Horticultural Society Magazine, The Garden, with a feature of Evening Primrose. Graham Rice describes the ‘yellow biennial evening primroses’ as a ‘confusing group based around Oenothera glazioviana. He says this species crosses with other species such as Oenothera biennis to create a ‘mixed-up group of similar hybrids’. That’ll do me!

Whenever I hear the words ‘evening primrose’ I add the word ‘oil’. Also called King’s Cure-all, evening primrose is said to have various healing and other good things. The seeds contain fatty acids that may, or may not, help in the control of certain illnesses. The considered opinion at the moment seems to be that clinical trials are inadequate to prove any real value but the chemicals are interesting and worth pursuing further.

So I won’t be harvesting the seed for medicine but I’m happy for it to spread a little further into the diminishing part of our garden that we can called neglected.

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Tim Entwisle

About Tim Entwisle

Dr Tim Entwisle is a scientist and scientific communicator with a broad interest in plants, science and gardens, and Director & Chief Executive of Royal Botanic Gardens Victoria. Previously he was Director of Conservation, Living Collections & Estates at Royal Botanic Gardens Kew and prior to that, Director of Sydney’s Royal Botanic Gardens for eight years. Read Tim's full blog at Talking Plants

4 thoughts on “Evening primrose – confusing & mixed up

  1. Ian E M itchell on said:

    Dear sir, I have been searching the internet trying to identify a plant that has suddenly appeared in my garden. unless it came as rogue seed in other seeds. or has been windblown I am at a loss as to what it is.
    I think that it is a type of “Oenothera”, but it is non of those I have found to date.
    I could send you a photo if this is possible, however I will try to describe it as best I can.
    The leaves are lance shaped up to 125mm long and 18mm at the widest point’
    Currently the leaves form a shuttlecock, or crown shaped, not growing up and along a central stem.
    Each leaf has a central red vein with the red colour bleeding slightly into the surrounding leaf tissue.
    The flower stem rises centrally and again is mostly red but darker than the red in the leaves.
    Single flower buds come direct from this stem with others spread at 25/30mm between each other.
    The first flower opened 5 days ago and began to wither the following day, the second flower is almost ready to open probably fully open tomorrow.
    I have only grown evening primroses once before and these reached 1m+, but they had green leaves all up the stems. It could be that this plant is quite common, but I have not come across it before so if you can help I would be very grateful .
    Thanking you for any advice or comments you can offer.
    Very best regards Ian E Mitchell

  2. tentwisle on said:

    Unfortunately I’m not sure Ann. As I say above it’s all very confusing. Best to get a botanist from the Northern Hemisphere to help out. Sorry about that!

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