The trouble is, they flower without any foliage. They share this odd strategy with several other late summer/early autumn flowering bulbs, such as the belladonna lilies and true autumn-flowering species of crocus which carry their leaves over spring when there’s decent soil moisture, but flower in late summer/autumn (and thus presumably avoid the high-traffic spring-flowering zones, when loads of plants are competing for the attention of pollinators).
This doesn’t present a challenge to growing them, as such. It only makes them difficult to place effectively in the garden. They can look a bit odd, and don’t benefit visually from being surrounded by a sea of bare soil when in flower.
I confess I hadn’t considered the potential for companions until seeing a pic about 25 years ago in Christopher Lloyd’s The Year at Great Dixter, showing the flowers poking through a carpet of the felted grey leaves of Helichrysum petiolare. Stunning.
(If you don’t know what the Helichrysum looks like, see a pic here. None of it in combo with the colchicums, unfortunately).
Finding a good companion isn’t easy. The colchicum has big, juicy, coarse leaves for months over spring, and overshadows, weakens, and usually kills anything in its immediate vicinity. The companion, therefore, must come into leaf exceptionally late so as to not mind this, or else be planted each year after the foliage of the colchicum fades. That’s what CL did with his Helichrysum. Young plants would be tickled in around the bulbs in early summer, then would rapidly and conveniently fill the space, and eventually provide a lovely background when the flowers emerged.
So why not just copy the idea? I’ve never understood why this should be, but my observation is that the Helichrysum tends to grow nearly prostrate in the UK, but seems to want to grow upwards here. Perhaps we have different varieties, or maybe its something to do with the climate. All I know is that if I tried the same combo here, the colchicum flowers would be trying to puncture through a solid shrub at least .5m in height by late summer. It simply wouldn’t work.
This year I decided I’d try that brilliant silver form of Dichondra (D. ‘Silver Falls’. Check it out here) as an undercarpet. It didn’t quite work, as the Dichondra is simply not cut out for the desert conditions that this summer applied. It survived, but never spread enough to get between the bulbs. But I suspect that it would also have failed visually, as the flowers of the colchicum are a bit on the pale side, and the silver foliage didn’t really make them sing. (There was enough of the silver nearby that if I squinted and lined them up carefully, I could imagine the overlap)
So now I’m thinking that I want a deep purple carpet instead. I’m therefore considering using Sedum ‘Bertram Anderson’ (Check it out here). I’ll have to plant it far enough away that it’s not composted by the colchicum foliage each spring, or else plant fresh cuttings of the sedum around the bulbs every year in early summer. The advantage of the latter is that the Sedum may then not make it into flower – it’s only the leaves I’m after. Sounds like a lot of work, but I’ll give it a go.
Anyway, you can see the challenge. Any ideas?