Plant of the Month September 2016

Posted on 31.08.2016 |
Updated on 04.09.2016 |
Added in Plant of the Month

I'm sorry that the word ‘jewel', applied to gardens, has received such celebrity endorsement over the last few years. A bit like Hovis and the New World symphony, it has given it a ubiquity that de-values its description of a very particular characteristic. September is a special month, when the quality of light and the effects of cooler temperatures bring a glowing depth of colour to the garden that truly merits the term ‘jewel-like'.

This month's plant (and it's no coincidence that jewels spring to mind – is ‘ruby' or ‘amethyst' more apt?) is Sedum ‘Red Rum', with amethyst flowers and lustrous dark leaves. Flowering begins in August when the leaves are deep sea-green, and lasts well into September, by which time the leaves are juicy and dark and the flowers rich crimson. Small in stature at around 15” tall, it doesn't spend the summer getting vast and fleshy then keeling over, as some do in heavy soil. The flower heads are not over-large but perfectly in proportion. I was asked at a recent HPS meeting why I would choose this as a dark-leaved cultivar over S. 'Purple Emperor' and the answer is that each starry, burgundy inflorescence seems to smoulder, while ‘Purple Emperor' has a greyish look. Leaf colour of these forms seems to improve with drainage and sunlight.

The tendency to top-heaviness in sedums can be dealt with successfully in two ways. The first is the well-known Chelsea chop, which not only works well but provides perfect cutting material into the bargain. The second is a little more drastic: taking a strong-handled fork, lever your clump a little way out of the soil, until you can feel a few (not all!) roots begin to give. Then allow your plant to sink back into place, from where it will grow neatly and compactly. This appears to have the same magical effect as standing up close to a seed- grown wisteria and saying loudly, ‘Of course, if it doesn't flower this year, it'll have to go.' A threat to mortality seems to have a similar galvanising effect on us all.

Propagation is simple – sections of stem root easily, preferably before flowering has started. Material from your Chelsea chop is perfect, 3” lengths around the edge of a pot of gritty compost. In light soils, seeding can be a nuisance (or a delight, depending on your point of view). Just make sure your named cultivars stay aloof and separate from the proceedings. Pot grown plants can suffer from vine weevil – keep an eye out for wilting, and top growth that comes away in your hand – but I've not so far had a problem with plants in the ground. As our resident Western Counties entomologist Michael Leach reminds us, vine weevil is a well-established British native, so isn't going anywhere, anytime soon. This cultivar is popular with bees, less so with butterflies.

This richness of tone is evident in other end-of-season planting companions: Aconitum carmichaelii in midnight blue, Phlox ‘Le Mahdi' in royal purple, glowing orange Crocosmia ‘Zambesi', cerise Fuchsia ‘Empress of Prussia', Aster ‘Prairie purple', sky blue Geranium ‘Roseanne' – a potent mix certainly. But this is a time of year that calls for intensity of colour, a last flamboyant gesture at the close of summer, so give it all you've got and make it a September to remember.

Posted by Gill Mullin