Plant of the Moment – No.10 Dahlia 'Arabian Knight'

Dahlia 'Arabian Knight' – young flower

D. 'Arabian Knight' – older flower

Much as I would love to able to grow dahlias in the open ground as part of our mixed borders, our astonishingly abundant slug population and organic principles make that an impossibility. We don't have a problem with underground damage to tubers; simply decimation of shoots and leaves... Even if we protect the young crowns, once growth is more developed and the foliage intermingles with that of neighbouring plants, the marauding hordes of molluscs have easy access across leafy air bridges. We now grow our dahlias in pots, and there is a small collection in full flower outside the office window as I write.

Star of the show is Dahlia 'Arabian Knight', which opens as the darkest of burgundies – almost blackish in fact and with a voluptuous, velvety texture – gradually lightening to blood red on the outer petals as the flower expands and ages. Joining 'AK' are the dark-leaved, orange-flowered 'David Howard' and a rather welcome imposter sold to me as 'David Howard', but which clearly isn't. Anyone got any suggestions as to its true identity?

The pots need daily watering – with a dose of tomato feed included at least twice a week – and regular dead-heading. We have copper tape around the outside of each pot and a copper ring around the crown of each plant. These do a good job in keeping slugs at bay and we have had hardly any damage this year – helped by the mainly dry, slug-unfriendly weather, of course. In late autumn I cut the stems flush with the compost and store the pots under the greenhouse staging, keeping them dry throughout the winter, only watering again in early spring. The young shoots make easily struck cuttings in May.

D. 'David Howard'

An imposter in the ranks – D. 'Not David Howard'!