Witch alder
This is a genus of two species of low growing deciduous bushy shrubs originating in woodland and swampy areas in the south east of the USA. They are fully hardy in the UK. The smaller growing of the two F. gardenii grows only to around 3ft with a similar spread eventually which makes it more suitable as a border shrub. F. major (F. monticola) grows rather larger and can reach up to 8ft in height with a spread of about 6ft. This makes it more suited as a woodland garden shrub.
Both species have white bottle-brush shaped flowers which appear in spring. F. gardenii flowers before its leaves emerge while F. major tends to flower later at the same time as its leaves appear. The flowers have white filaments and appear in terminal spikes. Those of F. major are scented and are a head turner in the rare plant tunnel in the nursery when in flower.
Both species have alternate and or obovate leaves which are dark green and have toothed margins. It is the splendid autumn colour which both these species of Fothergilla produce in autumn which makes them such valuable garden plants. The leaf colours are a bold mixture of red, orange and yellow and stand out in the border or woodland landscape.
These plants are fully hardy but they will flower better if some of the older stems are pruned out from time to time to encourage more fresh new growth. Well drained acidic soil is needed and you will get more flowers and better autumn colour if both species are grown in full sun rather than partial or dappled shade.
Seed only germinates a year after spring sowing. Softwood cuttings taken in summer are problematical to root or so we have found.
Fothergilla x intermedia ‘Blue Shadow’ is a hybrid between the two species bred in the USA with distinctive grey-blue summer foliage and rich red autumn colour. It grows to around 6ft in height.