If you need assistance managing your trees, contact an arborist to assess their health and your safety. Be sure to find a qualified arborist.
Tree safety
Title: Recognizing Tree Risk
Sponsoring organization: International Society of Arboriculture
Description:Three-page guidance on how to identify and manage tree risk.
Title: Managing Hazards and Risk
Sponsoring organization: International Society of Arboriculture
Description: This website provides helpful information about recognizing tree risk, storm-related tree damage, and avoiding tree damage during construction.
Pruning and Arborists
In Westchester County most private arborists will inspect the condition of your trees at no charge. Make sure the arborist is certified by the International Society of Arboriculture (ISA) or another recognized program or government agency as a tree expert, and is insured. After the inspection for any pruning or pest issues, the arborist will give you a work proposal setting forth costs. When you make an appointment for the inspection, confirm whether this will be the procedure.
Title: Why Hire An Arborist?
Sponsoring Organization: International Society of Arboriculture
Description: Discusses International Society of Arboriculture (ISA) certified arborists’ expertise regarding the care of trees. They provide services such as; pruning, tree removal, emergency tree care, planting and plant health care.
Title: Tree Care Tips and Techniques
Sponsoring organization: Arbor Day Foundation
Description: Scroll down to “Pruning” to learn why it is important to prune and when to prune.
Title: Ask an Arborist: Why Do I Need to Prune?
Sponsoring organization: Arbor Day Foundation
Description: Two-minute video for residents explaining reasons for pruning--safety of people, health of the tree, and aesthetics.
Title: Ask an Arborist: The ABC’s of Pruning
Sponsoring organization: Arbor Day Foundation
Description: A 5-minute video demonstrating the basics of tree pruning, primarily done in winter.
Title: Ask an Arborist: What Are the Rules of Pruning?
Sponsoring organization: Arbor Day Foundation
Description: A 3-minute video demonstrating pruning instructions, primarily in winter.
Japanese barberry is a dense, deciduous, spiny shrub that grows 2 to 8 ft. high. The branches are brown, deeply grooved, somewhat zig-zag in form and bear a single very sharp spine at each node. The leaves are small (½ to 1 ½ inches long), oval to spatula-shaped, green, bluish-green, or dark reddish purple. Flowering occurs from mid-April to May in the northeastern U.S. Pale yellow flowers about ¼ in (0.6 cm) across hang in umbrella-shaped clusters of 2-4 flowers each along the length of the stem. The fruits are bright red berries about 1/3 in (one cm) long that are borne on narrow stalks. They mature during late summer and fall and persist through the winter. Visit the Plant Conservation Alliance’s Aline Plant Working Group site to learn more about it as well as page 20 of the 
Black Swallowwort is a member of the Dogbane family (Apocynaceae). A six-to-seven-foot vine with long oval leaves. Tear-drop seed pods contain hundreds of seeds each with a tuft of white hair. Flowers are dark purple.. 
A deciduous bushy shrub in the bittersweet family (Celastraceae). Grows to 20 feet tall. Green to brown stems have corky wings. Elliptic leaves are one to three inches long and ½ to 1 ¼ in wide and turn bright red in the fall. Small green flowers occur in the spring and small tooth red-orange fruits turn purple in the fall. To eradicate it, hand pull seedlings up to two feet tall. Larger plants must be cut or dug out. Learn more on how to control it and review additional photographs on 
Phragmites australis is a non-native, invasive, wetland, perennial reed grass. Phragmites spreads aggressively by rhizomes and seeds and quickly outcompetes and displaces native salt marsh vegetation while providing little or no food or shelter for most saltmarsh-dependent wildlife. Additionally, Phragmites can eliminate small intertidal channels and decimate pool habitats that should offer natural refuge food for invertebrates, fish and waterbirds. Non-native Phragmites is distinctive due to the extensive dense colonies it forms and plume-like seedheads that generally persist through the winter on canes that range in height from 6 feet-15 feet tall and remain standing throughout the year. For more information go to the 
English Ivy is a non-native invasive evergreen vine that covers and kills trees. Vines climbing up tree trunks envelope branches, blocking sunlight from reaching the host tree’s foliage, impeding photosynthesis. For additional information look at 
Giant Hogweed is a Federally-listed noxious weed. The sap, when combined with sunlight and moisture (sweat), can cause severe burns and scarring. It can reach a height of 20 feet. The thick, hollow stems have dark purplish blotches and raised nodules. The leaves are compound, lobed, and deeply incised and can reach up to five feet in width. White umbrella-shaped flowers, resembling the flowers of Queen Anne’s lace, appear in early to mid-summer. It grows in disturbed places like roadside ditches and stream banks and prefers rich moist soil and full to partial sun.
Glossy Buckthorn is a deciduous shrub or small tree easily identifiable by its thornless branches and stems, which are covered by fine, wooly brown hairs. The leaves are simple, dark green and shiny on top. It prefers moist soils and tolerates sun, but thrives in shade. It is commonly found in disturbed places like roadsides and fields. Glossy buckthorn has insignificant yellow-green flowers at leaf axils in spring. followed by dark purple berries in summer and fall. The bark is dark gray or brown with white lenticels.
Japanese Angelica Tree is a member of the Carrot family is capable of growing forty feet high. This species blooms white flowers wider than they are tall in late August. Stems are covered in sharp spines and small purple fruits generally appear in September. Manual hand pulling and digging of young plants. A weed wrench much be used for larger plants. May be confused with Devil’s walkingstick (Aralia spinosa).
Japanese knotweed is a lump forming, semi-woody perennial three to 10 feet high. It produces sprays of small greenish-white flowers in late summer. The hollow stems are smooth with purple specks and have distinct nodes at leaf attachments. It is shade tolerant, thrives in a variety of soil and moisture conditions, and is commonly found along streams, rivers, or disturbed areas. Japanese knotweed can best be identified by hollow, bamboo-like stems with purple flecks and prominent nodes at leaf attachments. In late summer, sprays of green-white flowers are evident. Leaves are simple, alternate and generally oval with a flat base and pointed tip. New leaves may start out red and turn green in maturity. To learn more about it, how to control it and to see additional photographs go to the 
An annual grass growing up to 3 feet but often shorter. It forms dense stands in woodland edges and semi-open areas. It prefers moist, partially shaded sites but tolerates full shade. Go to Lower Hudson 
Jetbead is a multi-stemmed deciduous shrub that invades understories despite shade. Most noticeable for its flowers. Grown as a desired ornamental in China and Japan, it quickly outcompetes native shrubs and can grow five to seven feet tall disturbing canopy layers. Single, white showy flowers appear on sprawling shrubs in early May often at forest edges. The berries grow perpendicularly to each other and are jet black. Leaves are deeply veined, elongated and toothed - they grow directly opposite of each other.
Lesser celandine is a member of the buttercup family, lesser celandine is a spring ephemeral with glossy yellow flowers and dark green, heart-shaped leaves. It forms dense mats in riparian corridors, forested floodplains, wet meadows, and lawns, preventing the growth of other plants. By summer, lesser celandine dies back and disappears completely. The plant propagates primarily by small potato-like tubers that can be disbursed by water and digging animals. Once separated from the parent plant, each tuber has the potential to grow into a new plant.
Mile a Minute is a species of flowering plant in the buckwheat family. Also called Devil’s tearthumb, it is a trailing annual vine with barbed stems and triangular leaves. It is vigorous, and smothers other herbaceous plants, shrubs and even trees. To learn more about it, how to control it and to see additional photographs go to the 
Clump-forming invasive perennial flowering herb with woody stems up to 5 feet high and deeply lobed alternate leaves with hairy undersides. Blooms July - October. Often found on forest edges, roadsides, waste places and in turf grass, as well as home gardens. When crushed, leaves have a spicy, sage-like aroma. It was introduced into North America from Europe and Eastern Asia, where used medicinally, primarily as a digestive. Spreads aggressively, primarily by rhizomes, and is highly threatening to native plants. To learn more about it, how to control it and to see additional photographs go to the 
Dense efflorescent shrub first introduced from Asia that spreads rapidly in open woods, pastures and woodland edges and can climb into trees. Reproduces by dispersal of millions of seeds that may remain in the soil for twenty years and are widely distributed by birds. Creates large, impenetrable thorny, thickets that exclude native plants and inhibit movement and foraging of native wildlife. To learn more about it and see additional photos, please visit the Lower Hudson 
Norway Maple is a widely distributed invasive tree that outcompetes all other terrestrial species by virtue of producing dense, dark shade and exuding chemicals from roots that impede growth of other plants. Trees support almost zero species of insects, birds or wildlife. A milky white sap is exuded when a petiole is detached from a tree or veins of leaf are cut. The sap of other maples is clear by comparison. It has broad, full leaves with narrow tips at the end that stay green late into the fall. Additionally, the pattern of the bark is up and down and it is deeply grooved. It may be confused with the Sugar maple and Red maple
Oriental Bittersweet is a climbing perennial/woody plant that is known for its colorful red fruit and spade-shaped leaves. This fast-growing vine often wraps and strangles the surrounding vegetation, including trees, becoming thicker with age. It has white/green blossoms in spring and is spread by birds and by people who find it attractive. To learn more about it and to see additional photographs go to the 
Oriental Lady’s Thumb is an annual that produces thousands of hard-coated seeds and distinctive pink flowers. It can grow as long as six to 30 inches, either erect or sprawling. Oriental lady's thumb is classified as a widespread nonnative species that is restricted to disturbed areas and is not invasive in undisturbed habitats
Purple Loosestrife is an herbaceous, multi-stemmed wetland perennial up to two to three meters tall, becoming woody at base. Has opposite leaves with smooth margins, and a terminal spike of showy, pinkish-purple flowers.
Spotted lanternfly is an invasive pest from Asia that poses a very significant threat to New York’s agricultural and forest health.
Tree of Heaven is a fast growing, colony -forming deciduous tree of disturbed places. When crushed, the leaves and branches have a distinctive smell often compared to rancid peanut butter. Tree of heaven tolerates a variety of soils, and sun or shade conditions. It is the preferred host of the invasive insect, Spotted Lanternfly. Tree of heaven flowers in June with showy clusters of small, yellow-green flowers, which are followed by papery winged seeds (samaras) in late summer and fall. The compound leaves have 10-40 leaflets with smooth leaf margins. Each leaflet has one or more rounded teeth near its base with a thickened gland on the underside of each tooth. When crushed, leaves and branches release an odor often compared to rancid peanut butter. Learn more about it and review additional photographs on 
Wineberry, a member of the Rose family is a deciduous shrub with thorny canes that can grow up to 9 feet in length. These arching, thorny canes can be identified by their distinctive red hairs, but most easily identified in July when their raspberry-like fruits are present. Please see the Lower Hudson 
Yellow Flag Iris (Iris pseudacorus) also known as the Yellow Flag, Yellow Iris, or Water Flag