Belonging to the family Salicaceae,

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1 The Wild & Diverse World of Willows By Dr. Julia Kuzovkina Belonging to the family Salicaceae, the genus Salix comprises about 450 species. It is distributed worldwide but occurs mostly in the Northern Hemisphere. Willows occur in several forms: large and small trees, shrubs, and groundcovers that are only a few centimeters tall. Their habits vary from upright, to pendulous, to spreading. Willows are tolerant of a wide range of climates. Predominantly occurring in temperate and arctic zones, they re also found in the subtropics and tropics. Willows are the only woody species in some alpine zones known as zones of dwarf willows. They also play an important role in the vegetative cover of tundra and areas above tree lines. The center of abundance of willows is in China, with almost 200 native species. There are 113 species inhabiting North America, including some 22 species native to New England. New England species are mostly lowland species. See photos 1 and 2, and the chart on page 27. Five species S. arctophila, S. argyrocarpa, S. herbacea, S. uva-ursi and S. planifoia have narrow distributions in alpine ravines in northern New England. In addition to the natives, a few introduced species are listed in New England floras, of which the most common include S. alba, S. atrocinerea, S. caprea, S. cinerea, S. x fragilis and S. x sepulcralis (weeping willow). See chart on page 27. Ecology Species of Salix differ in their ecological requirements, although the majority of them are adapted to moderately moist (mezic) and wet (hydric) habitats. Moisture availability is an important factor controlling native distribution and abundance of the species. Willow seed, which is seated in a ring of fine hairs that facilitate dispersal by wind, contains chlorophyll but no endosperm and has limited longevity. In order to germinate, seed must be exposed to moist surfaces within a few days. Abundant moisture is important during seed germination and early seedling establishment. However, after that stage, constant soil moisture is not as important to the survival of many willows. When established, some species can survive extreme water fluctuations and 23 1 prolonged periods of partial inundation. Their ability to withstand root exposure and heavy sediment deposition, or burial, as a result of water and wind erosion, relies on adventitious rooting of buried stems and the flush or break of dormant buds. continued on next page Most people know about pussy willows, which are collected in the spring for decorative arrangements, or weeping willows, which are widely planted as ornamentals throughout the region. However, there are 22 species native to New England. The attractive Salix lucida, shining willow, is among them. Photo / M. Dodge, Vermont Willow Nursery Stands of Salix nigra and S. amygdaloides along Lake Champlain in Vermont. 2 3

2 The Wild & Diverse World of Willows continued from previous page These adaptations allow willows to survive in the constantly changing environments of flood plains, water margins and sandbars. Riparian or alluvial species (for example, S. nigra and S. alba) growing along river valleys, stream banks and lakeshores, require well-aerated substrate and flowing moisture. Nonriparian species, such as S. discolor and S. petiolaris, are less exacting in soil aeration requirements and include wetland species that are well adapted to saturated soils. See photo 3. Some willow species are even adapted to drought and heat stress and exhibit xeric traits. For example, S. humilis, S. tristis and S. cordata inhabit sandy roadsides, plains and sand dunes. See photo 4. The ecology of willows also includes the strategy of early successional plants colonizing newly opened habitats. These comprise manmade habitats such as abandoned agricultural fields, railroads, old mine tailings and gravel pits. They also include recently burned, glaciated (soilless) or flooded areas where disturbance results in an open community with low competition levels, allowing a temporary increase in the dominance of opportunistic species. Identification Salix is a difficult genus to identify at the species level due to considerable individual variability, interspecies hybridization other factors. In addition, in precocious species, the flowers appear before the leaves. This non-concurrent phenology of flowers and leaves make the simultaneous observation of important morphological characteristics nearly impossible. It is useful to know a set of characters representing distinctive morphological features for each species to be certain that identification is positive. For example, S. interior from the subgenus Longifoliae, which comprises only a few New World species, has long linear leaves with stomata on both sides, a leaf margin with remote dentation (the teeth are far apart) and branched catkins. S. interior propagates by root suckers, forming dense thickets. In nature, clonal propagation is unusual Salix cordata on sand dunes along Lake Ontario in New York. in Salix and only species from Longifoliae form root suckers. See photos 5 and 6. In winter time, buds can assist in identification of some species. Two kinds of buds are found on willow stems: generative flower buds and vegetative leaf buds. In Salix discolor, which flowers early in the spring, very distinct large flower buds occur mostly on the upper portion 4 Become a Master Composter Interested in becoming a Master Composter? Classes will be held on Thursdays, Oct. 5, 12, 19 & 26, 6-9 pm at the Fairfield County Extension Center in Bethel. $100. Details at ladybug.uconn.edu 5 Salix interior with long narrow leaves (left) and female catkins borne on distinct flowering branchlets (right). 24 6

3 of the branch, with smaller leaf buds occurring below the inflorescences. In S. nigra and S. amygdaloides, leaf and flower buds are uniform in size and shape and are not distinguishable. See photo 7. The sequence of flowering and the development of shoots vary among species, and few patterns of annual development are recognized. Precocious species, such as Salix sericea and Salix discolor, flower before leaves emerge. Species with this habit Salix humilis in early spring. 8 typically have sessile catkins (flowers). The flowers are borne directly on the stem, there is no pedicel or stalk. See photos 8 and 9. In subprecocious species, Salix bebbiana for example, generative budburst and flowering occur just before the emergence of leaves. Catkins of species with this habit are sessile and borne on short, flowering branchlets. In coetaneous species, flowering and leaf emergence take place simultaneously. In Salix lucida, Salix nigra and 25 Salix sericea (left) and Salix discolor (right) two New England native species that are precocious (the flowers emerge before leaf break). 7 9 Salix serissima, the flowers are borne on distinct flowering branchlets. All willow species are dioecious with male and female catkins occurring on separate plants. Single-sex flowers are arranged into mostly upright catkins. Salix flowers are predominantly insect pollinated, but wind pollination takes place as well. See photo 10. Each willow flower has a variable number of nectariferous glands or nectaries. Because flowering takes place in early spring, willows are very important for pollinators, providing both nectar and pollen. e roots of a some tree-type willows (such as weeping willow and white willow) can damage underground structures and should not be planted near houses. Shrub-type species have an extensive fibrous root system with the majority of fine roots found in the upper centimeters of the soil profile. Most willows form root primordia on stem nodes and root easily. A few species form root suckers (S. interior), create small colonies by layering (S. humilis), or propagate vegetatively by broken branches that are brittle at the base (S. nigra). Utilization The uses of willows are as diverse as the biodiversity of the genus. Indeed, willows have a long history with humans. Indigenous peoples in North America and Eurasia used willow bark infusions as analgesics and for at least two centuries before the synthetic production of aspirin, salicin extracted from Salix bark, was commercially exploited. Flexible willow stems were also the primary material for basket production and straight willow branches were used for arrow shafts, fish traps and numerous other items. More recently, willow was proposed as a biomass crop for bioenergy and bioproducts, representing promising feedstock crop in many countries. Its plantations can be productive for 25 years due to plants ability to resprout from stumps after repeated harvesting so called coppicing. continued on next page

4 The Wild & Diverse World of Willows continued from previous page The primary focus on willow production has expanded over the past decade to include various conservation and environmental goals. Today, willow is cultivated not only to produce biomass for energy, but also to filter various waste products through contaminant uptake from the soil and water, and is adapted for many environmental applications, such as phytoremediation, riparian buffers and shelterbelts. They are also widely used for reclamation of disturbed sites where Salix species anchor a pioneer community, accelerating the recovery of damaged preparation of willow stems for basketry Photo / M. Dodge, Vermont Willow Nursery Generative buds contain embryonic flowers with rudimentary leaves that form during the preceding year and continue development throughout the winter, resulting in gradual expansion of the inflorescence until it pushes off the bud scale. Each flower in the inflorescence is subtended by a floral bract with dense hairs these bracts create the pussy willow effect in some species. Biomass plantation in New York after coppice

5 ecosystems and the re-establishment of natural ecological complexity. See photos 11 and 12. Julia Kuzovkina is an associate professor at UConn. She received her doctoral degree in horticulture from Ohio State and a master s in botany from Moscow State University. Dr. Kuzovkina s research has focused on environmental horticulture, phytoremediation and selection of plants for environmental applications. Julia Kuzovkina Willows and Some of Their Common Names New England Species S. amygdaloides peachleaf willow S. bebbiana Bebb s willow S. candida sageleaf willow S. cordata sand dune willow S. discolor American pussy willow S. eriocephala Missouri River willow S. exigua sandbar willow* S. humilis prairie willow S. interior sandbank willow S. lucida shiny willow S. myricoides bayberry willow S. nigra black willow S. occidentalis dwarf prairie willow S. pedicellaris bog willow* S. pellita satin willow S. petiolaris meadow/slender willow S. pyrifolia balsam willow S. rigida heartleaf willow S. sericea silky willow S. serissima autumn willow Narrow Distribution Alpine Ravines S. arctophila northern willow S. argyrocarpa Labrador willow S. herbacea snow-bed willow S. planifolia tea-leaved willow S. uva-ursi bearberry willow Introduced Species S. alba white willow S. atrocinerea rusty willow S. caprea goat willow S. cinerea gray willow S. x fragilis crack/brittle willow S. x sepulcralis golden weeping willow Sources gobotany.newenglandwild.org plants.usda.gov * Endangered species in Connecticut Species of special concern Bruce Martin, CC-BY-SA 2.5 Salix nigra at the Morton Arboretum in Illinois. Starting in September, the University of Connecticut s Cooperative Extension System will accept applications for its 2018 Master Gardener Program. Applications should be available online in late August at mastergardener.uconn.edu and at all County Extension Center offices and the Bartlett Arboretum & Gardens in Stamford. The program consists of 16 classroom sessions (one day per week) beginning the first full week in January and running through April. An openbook test, diagnostic session, final Right Willow, Right Place Nurseries that sell willows will have many varieties not mentioned here. Be sure to choose ones that are right for your location. Willows that are aggressive when left to their own devices may do just fine if they are pruned, coppiced or pollarded. Willows like water and their roots will proliferate toward water if they encounter it. Willows that propagate via root suckers and form dense thickets can take over stream margins quickly and are best left for use by professionals as an erosion control or for phytoremediation. Some introduced species, such as S. cinerea (large gray willow) and S. atrocinerea (rusty willow), readily invade riparian habitats, brackish Become a UConn Master Gardener in 2018 practicum and tree-shrub-vine identification project are also required. To graduate, you ll also need to do 30 hours of in-service training at one of nine office locations and 30 hours of volunteer outreach. The charge for the program is $425. wetlands and damp forests. Both of these closely related willows are considered invasive in Massachusetts. In Connecticut, S. atrocinerea is on CIpWG s research list, which means they want more information. Visit cipwg.uconn.edu for more information. You can report sightings of this willow to reportinvasives@uconn.edu On the other hand, S. exigua (sandbar willow) and S. pedicellaris (bog willow) are endangered in Connecticut and S. petiolaris (meadow or slender willow) is listed as a species of special concern. For more information, go to ct.gov/deep and search for endangered species. Will Rowlands Scholarships may be available based on demonstrated financial hardship. A completed application must be submitted to the location where you wish to take classes; at one of four County Cooperative Extension Centers or the Bartlett Arboretum. The deadline is usually in early November. This year, classes will be held in Stamford (Monday), Norwich (Tuesday), Torrington (Wednesday), North Haven (Thursday) and Vernon (Friday). For more information, call your local Cooperative Extension Center or visit mastergardener.uconn.edu 27