Fothergilla species are deciduous, Eastern US natives that are truly spectacular, four-season shrubs. In early April the white, 1½ to 3-inch tall, bottle-brush blooms appear with their delightful, honey-like fragrance. Flowers typically last for 2 to 3 weeks, and then are replaced by beautiful, green to blue-green, quilt-like foliage. Fothergilla leaves are extremely similar to those of witchhazels, which are in the same plant family, Hamamelidaceae.
The fall brings the showiest display for fothergilla, and every year seems to be slightly different. During November, the frost-tolerant foliage takes on golden-yellows, bright oranges or intense reds, or combinations of all. Weather conditions greatly influence the autumn coloration each year, with the amount of sunlight, rainfall and temperatures all playing a role.
Once the autumn foliage is gone, the interesting zig-zag branch habit of these upright, small shrubs is seen and adds to winter interest.
There are only two species of fothergilla in the Eastern US, large fothergilla (Fothergilla major) and dwarf fothergilla (F. gardenii). The two species are almost identical, except for flower and leaf size, and overall dimensions of the shrubs. Large fothergilla may reach 6 to 10 feet in height, whereas the dwarf fothergilla may reach 3 feet tall.
In nature the two species do not grow under similar conditions. The dwarf fothergilla naturally occurs in the lower half of South and North Carolina where the soils are sandy, but in sunny savannahs and areas called pocosins, which are typically moist much of the year, acidic, and also organically rich. The large fothergilla is found in the mountains and Piedmont of South and North Carolina, under conditions of drier and heavier acidic soils, and in part-shade.
Several named cultivars have been available, but by far the most beautiful is a hybrid between the two species called ‘Mt. Airy’ (or ‘Mount Airy’). This naturally occurring hybrid was discovered at Mount Airy Arboretum in Cincinnati, Ohio by Dr. Michael Dirr of the University of Georgia. In this arboretum, both Fothergilla species grew near each other, allowing this cross to occur. Chromosomal studies at NC State University have verified that ‘Mt. Airy’ is indeed a hybrid of the two species. ‘Mt. Airy’ may grow to 6 feet tall, has intense fall color and larger flowers. It has been proposed to name the inter-species hybrids Fothergilla x intermedia, for example, F. x intermedia ‘Mt. Airy’. Most resulting crosses produce hybrid plants with heights in between those of the large and the dwarf plants (about 4 to 6 feet tall).
Fothergilla species and cultivars flower best when sited in full sun and also develop the most brilliant fall color. However, without weekly irrigation in the heat of South Carolina summers, fothergilla may perform better in part-shade, especially morning and early afternoon sun, coupled with late afternoon shade. They thrive in areas that have moist, but well-drained soils.
Fothergilla, especially ‘Mt. Airy’ and the dwarf fothergilla, work well in landscape designs for English mixed perennial and shrub gardens, border gardens and as accent plants in foundation plantings. They will tolerate a significant amount of shade, and therefore are good additions to woodland plantings where they compete fairly well with tree roots. They are reported to be deer resistant.
Plants sucker to form colonies, but this is more so for F. gardenii than F. major, especially where the smaller fothergilla naturally grows in looser, sandy soils. Pruning, if necessary, should be done immediately after flowering in late April.
Amending large landscape beds with organic matter is always better than simply amending a planting hole. Amendments containing composted (decomposed) pine bark will improve soil drainage, maintain the natural soil acidity that is important for these shrubs, and help suppress soil-borne disease. However, leaf compost may be used. All forms of organic matter help the soil hold on to applied nutrients for the plants to slowly utilize.
In general, amend the soil with organic matter to 10 to 20% by volume. This will make for a very good quality soil without extensively changing the soil structure. For a landscape bed, evenly apply a 1 to 1 ½-inch deep layer of organic matter over the planting bed, and then thoroughly mix by tilling to 6 or 7 inches deep. As these shrubs require an acidic soil, choose a site that has not been limed in recent years. Fall is the best time to plant most shrubs as roots will grow during the fall and spring months to better establish plants before the heat and drought begin in the summer.
Because of the need for acidic soils, acid-forming fertilizers are the best to use. Examples of complete organic fertilizers for acid-requiring plants are Espoma Holly-Tone (4-3-4) or Fertrell Holly Care (4-6-4). Examples of appropriate slow-release fertilizers are Lilly Miller Ultragreen Azalea, Camellia & Rhododendron Food (10-5-4) or Ferti-lome Azalea, Camellia & Rhododendron Food (9-15-13). A soil test can help determine the best fertilizer analysis to choose. Fothergilla species are typically slow growing shrubs. To encourage faster growth, fertilize twice during the spring, such as on April 1st and again in mid-May to cover the main spring growing period. Apply mulch to landscape beds.
Fothergilla seeds are somewhat difficult to germinate and may take 9 to 15 months to germinate, depending upon the species. Softwood cuttings, or cuttings from suckers or root pieces, are relatively easy to root and produce new plants. Softwood cuttings are generally the most plentiful and available of the three, and the best time to collect cuttings is between June and mid-August.
For most deciduous shrubs, June is the best time to collect cuttings for greatest success.
Cuttings can be rooted in a 1:1 peat and perlite medium, or use a fine-grade potting soil that is made for seed germination and mix it with an equal part of perlite. The rooting of cuttings will be more successful if a rooting hormone is used, especially one such as Dip ‘N Grow Liquid Rooting Concentrate. However, if not available, any powdered rooting hormone will improve success.
Once rooted, if the plants are actively growing, they can be transplanted into larger containers. If they are not actively growing and are transplanted, they may not survive. In the latter case of not actively growing, leave the rooted cuttings in the smaller containers to over-winter with some cold protection. When new growth begins in the spring, repot them into larger containers. The advantage of taking cuttings in June rather than later is that when the cuttings become rooted, it is still warm weather for additional growth to occur.