Acer saccharinum aka Silver Maple

Silver maple, Acer saccharinum, is a large deciduous tree in the soapberry family, Sapindaceae. Other names include soft maple, white maple, river maple and swamp maple. It grows wild across eastern and central North America, from southeastern Canada into the central and eastern United States. In the wild it lines streams and rivers, floodplains and low, wet woods.

In gardens it usually reaches 50 to 80 feet (15 to 24 m) tall and 40 to 60 feet (12 to 18 m) wide. Old wild trees can pass 100 feet (30 m). The trunk is often short and splits into several stems. Long branches arch downward and then turn up at the tips. Together they form a rounded or vase-shaped, open crown.

Young bark is smooth and light gray. With age it breaks into long, thin strips that curl loose at the ends. These strips reveal orange tones beneath. Young twigs are glossy red-brown and smell unpleasant when crushed. The opposite leaves are 2.5 to 5 inches (6 to 13 cm) long, with five deep palmate lobes and coarse teeth. They are green above and silvery white below, so the tree shimmers in a breeze. Autumn color is mostly yellow, sometimes with orange or red tints, though many trees color poorly.

Small greenish-yellow to reddish flowers open in dense clusters in late winter or early spring. They appear well before the leaves, often in March. Bees visit them as an early nectar source. The fruit is a paired samara, the largest of any native maple, with wings up to 2.5 inches (6 cm) long. The samaras ripen in late spring and sprout almost at once. Squirrels, chipmunks and birds eat the seeds.

Silver maple grows fast and suits full sun or part shade. It is hardy in USDA zones 3 to 9 and rates H7 in the UK. It prefers moist, acidic soil and can stand weeks of flooding. It also copes with drought, poor soil, clay, compaction and city air. On soils above about pH 7.5 the leaves often yellow from chlorosis. Gardeners use it as a quick shade tree, in rain gardens, by ponds and on wet sites where little else thrives.

The main drawback is weak, brittle wood. Wind, ice and snow often snap limbs, so early pruning helps build a sound frame. Shallow, aggressive roots lift pavements and invade drains and septic fields. Heavy seed crops produce many unwanted seedlings, and fallen leaves and fruit create litter. Diseases include verticillium wilt, anthracnose, canker, leaf spot and tar spot. Scale insects, borers, aphids and gall mites may also attack.

People boil the sweet sap into syrup, though yields are lower than from sugar maple. Young seedlings and the cooked seeds are also edible. The wilted leaves are toxic to horses, with gallic acid named as the poison. Keep the tree away from horse paddocks.