Oenothera triloba
by Sue Leduc

Seed exchange lists are always very exciting to me. They are a fantastic source for some really unusual plants. I found one of these in the 2004/2005 OVRGHS seed exchange: Oenothera triloba. Thank you, Margaret H!

Oenothera triloba is in the evening primrose family. All prior experience with 'evening primroses' made me wonder why they had the word 'evening' in their common name. Now I know... at least for this species.

The foliage of this plant is not particularly remarkable, though attractive enough. The long, thin, deeply serrated leaves grow in a kind of rosette, like a dandelion that isn't getting enough light.

It's the flowers that make this plant truly amazing. They open about half-an-hour after sunset. But that's not what makes them so interesting - it's the speed at which they open. They go from buds that look like little okra pods to clear, soft yellow flowers, in about 60 seconds - fast enough that you can see them move! On the first night that we decided to watch the flowers open, I was killing time doing a bit of watering and not really paying close attention. I looked up and there was one flower fully open. We stopped what we were doing and, over the next 10 minutes or so, watched another 11 flowers open - like time-lapse photography in real time. It was astounding!

After a few days of watching them open every evening, we decided that it would be a good idea to collect the seed so we could share. And there should be lots of seedpods because there were between 8 and 12 flowers opening each evening. But when we squeezed the base of the spent flowers, where seed pods normally form, there was nothing there. It took a while, but we finally discovered the seedpods forming at the base of the flower stem, hidden in the foliage at ground level - more surprises!

But that's not all. They started blooming in late July and were still putting on their nightly show well into late September - and all in their first year from seed!

The seeds were very easy to germinate. In late March, they were sown in pots of ProMix, lightly covered with fine vermiculite and placed out on our fully enclosed, unheated porch. By late April, they were up. They were planted into the garden in early June, just around the time of the first heat-wave of 2005. They are in deep, lean, well-drained soil in full sun and seem to be quite happy.

About the only bad things that could possibly be said about this plant is that the flowers don't seem to have a scent, which is a bit odd for a night-flowering plant, and it's really hard to get a decent picture of the flowers because they've faded by the time normal people are getting out of bed.