As the mild winter draws to a close, a Canadian icon begins to celebrate the coming of a new horticultural season.
Sugar maple (Acer saccharum) is native to the hardwood forest of northeastern North America. It is best known for its brilliant fall foliage and for being the only source of maple syrup.
The sap usually begins to flow in March. With this exceptionally mild winter, trees are being tapped early.
Warm days (2 to 7C) followed by below-freezing nights (-4 to -6C) are required to start the sap flowing.
Those ideal temperatures produce the highest rates of flow. The best sap that has the highest sugar content runs early in the season.
Sugar maples are the best producing trees. Sap contains about 2% sugar, while other maples contain half as much. Syrup made from later saps is darker and less flavourful.
During the maple sugaring season, which lasts about 6 weeks, an average maple tree will yield between 40 litres of sap. That will produce one litre of pure maple syrup. Last year, four litres of syrup cost $50.
Beyond good weather, new technology has played an important role with vacuum tubes that pull sap from trees. New spiles (taps) have been developed with valves designed to prevent sap flowing back into the trees.
Maple trees with large crowns (top foliage) are the best producers.
Once tree buds begin to swell, collecting sap must cease. The tree requires the remaining sap for its new growth. Syrup producers know that the sap may still be flowing at that time, but it makes a poor quality product.
Sugar maples grow in a variety of soils, but grow best in deep, moist, and well-drained soils with medium or fine textures. They are commonly found growing with oak, beech, basswood, white ash, black cherry, yellow birch and white pine. As forests grow older, sugar maples will become the dominant species.
Mature sugar maples are large, with dense rounded crowns. In forests, their trunks are usually straight and free of branches for two-thirds or more of their height. In open spaces, trunks are shorter, with a few large branches supporting a wide crown.
Sugar maples can live to be 400-years-old, reaching heights of 20 to 35 metres and diameters of 50 to 90 centimetres.
Stands of maples are usually managed for either timber or syrup production. Both methods provide other benefits, such as improved wildlife habitat and cleaner air and water.
Sugar bushes are managed to produce the greatest amount of sap and to keep stands healthy. Stands are thinned out to produce broad, deep crowns, thereby exposing the trees to sunlight. Trees that are defective or diseased are removed to encourage new growth on healthy specimens and to prevent disease from spreading further. Trees and woodlots are also selected for the sweetness of their syrup.
Higher sugar content levels increase syrup production. Sugar content is determined by genetic and physical characteristics of trees.
Hard cold winters are necessary for the maple’s survival and sap production. Each fall, the tree provides a spectacular colour palette of yellow, orange and scarlet leaves.
The sugar maple or hard maple is the best provider of the highest quality sap. It can grow to 30 metres and is valued for its shade.
Sugar maples can reach a tappable size, under the best conditions, in about 40 years. Carefully tapped, a tree will give about 12 litres of sap on a warm spring day. Productive trees could conceivably give sap for a century.
Maple trees are subject to a fungal disease called tar spots. The name of the disease comes from black spots that can be found on the leaves. Willow and oak trees are also afflicted.
The disease looks similar on those plants with a thickened black layer on the upper side of the leaves. The size of the spots can range up to several centimeters across.
The sugar maple was designated as Canada’s national tree in 1965.
This column was submitted by Ron Stevenson, of the Fergus Horticultural Society.
