Plant of the Month: October

Allium cernuum – to buy or not to buy? That is the question.

by Sue Gray

I expect that, over the years, all of us have bought, or been given, plants that we have later regretted.  In my case the regret is usually associated with the performance of the plant, and how keen it is on world domination!  I think I am fortunate in having good loamy soil; I can claim no credit for this – it is what I inherited, which is as well as I am very bad at preparing soil for planting.  If there were an Olympic games for plants, I could nominate several plants for inclusion in a sprint relay, Silene fimbriata, Adenophora, Centaurea and some Phlox to name but a few, but in the main these can be controlled (with the exception of Japanese anemones!) by judicious digging out or, as a last resort, spraying with weed killer, but the ‘self-seeders’ are a totally different matter.

Allium cernuum

The plant that has been causing me particular anguish in recent years is Allium cernuum.  I know it is very attractive but it has got everywhere since I acquired it at a garden on one of our Group holidays some years ago.  I had decided that I would try and use as many bulbous plants as possible in one particular bed and, as they were so pretty, I think I might have even bought two pots.  First mistake.  I should have been ‘put on enquiry’ (as we used to say in my former working life as a bank clerk) by the fact that the garden owners had so many pots of it for sale; it has taught me ever since to be extremely wary of any amateur gardener with a lot of one particular plant for sale!  I brought them home, planted them, and over the years they have cropped up throughout the bed and in the gaps between the paving surrounding the bed.  Of course, they are no respecter of space and quite likely to appear in the middle of other established plants, as they have done in some clumps of, what I believe to be, Allium senescens.

Allium senescens

These alliums are much better behaved; they do not seed around but form clumps of semi-evergreen foliage about 25cms tall with slightly taller mauve flowerheads in mid/late summer.  As they bulk up so well, over the years I have split them and formed four good sized clumps, two in the front garden and two in the back, all of which had A. cernuum growing up through them.

I decided that the time had come to deal with the interlopers, but realised that to do so I was going to have lift all the clumps and try and identify which bulbs belonged to which allium.  As a first step, when the flowers of A. cernuum appeared, I cut the head off, thus hoping to prevent further seeding around, but leaving the stem which I should be able to trace back to the offending bulb.

A. cernuum on the left, one of the lifted clumps on the right

This actually proved to be easier than I could have dreamt, for when I lifted the clumps I discovered that A. senescens – if that is what they are – as opposed to A. cernuum, actually do not remain as individual bulbs, but join together, forming woody, root-like, structures below the bulb.  The clumps were so tight knit that they took some prising apart, but I hope I have managed to remove all the offending A. cernuum bulbs, many of which had already started sprouting in readiness for next year.  This image shows the individual bulbs of A. cernuum on the left and a section of one of the lifted clumps on the right.

An added bonus of this operation is that I was able to identify, and remove, a number of triteleia which, in my book, fall in to the same category as A. cernuum!

My only problem, now, is that as they were such good clumps, and I have only replanted a small portion of each, I have about 20 pots available for sale.  So, if you see me with them, please ignore my comments about amateur gardeners with lots of the same plants for sale, and relieve me of some.  I promise that they are very well behaved, and lovely additions to the mid/late summer border.

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