Gardeners like foxgloves, because they are among the easiest of plants to grow; in fact they grow themselves, reproducing in the darkest places. Groups of the common purple form are hardly likely to surprise anyone, but there are white and apricot- coloured versions of Digitalis purpurea that are well worth encouraging. They are no harder to please than the purple sort, but you do need to buy a packet of seed in one of these named colours to get them going.
If you want to restrict your foxgloves to a selected form but have allowed purple ones to self-seed in the garden, you have to be ruthless about pulling out the ones you don't want to keep - before they start to seed - because the common purple sort will always dominate. In time all seedlings will come up purple if you allow the usual ones to set any seed at all.
Some people say they can detect rogue foxgloves at the seedling stage by the dark vein in the leaf; but this is a slow business, fraught with indecision about whether the leaf really is veined or not. I would rather wait for the plants to flower, pulling them out as soon as the flowers fade. You may, however, want to keep the purple as well as the rarer versions of the common foxglove going; there are two ways to do so. The first involves buying seed of the uncommon varieties every year to sow in May, which will flower the following year. The second is to put plastic bags with pierced holes over the flowering spikes with the seed that you want to keep, so that bees do not pollinate and cause cross-fertilisation with the purple ones.
The Rusty Foxglove, Digitalis ferruginea, being a perennial, is much less complicated to grow. Seldom seen in gardens today, it is a curious colour, more copper than rust, and the 'gloves' are tiny and rounded. I like it for its height and strangeness, as well as for the fact that it flowers in late summer in shady difficult places. Digitalis ferruginea is a wild flower of the high Caucasian meadows, so officially it likes a cool moist soil. But, like all foxgloves, it is tolerant of some sun. This year it had so much rain and mulch that the stems have wobbled and grown to a great length, so starvation may suit it better.
The yellow foxgloves, lutea and ambigua, are also technically perennial, although ferruginea and ambigua make better clumps than lutea, which is a delicate member of the family. D lutea is pretty but not showy. The Rusty Foxglove looks grand because of its size, even though its flowers are not as large as those of a normal one. The creamy yellow gloves of D ambigua are standard foxglove size, but the plant is much shorter at around 2ft 6in. D lutea is smaller; its stem is short, 2ft 6in again, and its flowers are in proportion. Like all foxgloves they should seed themselves; the clump-formers keep going for longer, like any other clump-forming perennial, if they are occasionally divided.