Useful Maple ProductsMaple Syrup
A famous maple product is maple syrup, which European immigrants to North America learned to make from Native Americans. When taken from the tree, maple sap is crystal clear and does not taste sweet; its sugar content usually is only about 1 percent but can reach 3 percent for "very good trees." Not only did the early North American settlers learn how to collect maple sap and produce maple sugar, but more importantly they learned that Acer saccharum provided a substitute for very expensive cane sugar. Breaking out of dormancy, this species produces sap between mid-December and bud expansion in the spring. The sap flow is temperature dependent, occurring only following a rise in ambient temperature during the day and a fall in temperature at night. The rate of flow reduces as temperature decreases, but then increases again the next day with temperature increase. Sap is collected through a hollow tap driven into the tree trunk. When boiled down, 8 gallons (30 liters) of sap produce one gallon (4 liters) of syrup.
Acer saccharum ssp. saccharum is the major taxon of importance in the maple syrup industry, though A. saccharum ssp. nigrum, A. rubrum, and even A. saccharinum have spring sap flows rich in sugars. The latter three species are less frequently tapped because of their lower sugar concentrations. Most maple syrup is now produced in Quebec, Canada, and in a number of U.S. states, including New Hampshire, Vermont, New York, West Virginia, and Ohio. Chinese correspondents report that Acer species in China yield a sweet sap also (T. R. Dudley, pers. com.). Free-standing trees are much more productive than forest trees. While the mechanism of sap rising is poorly understood, it appears that a water pumping mechanism in the roots and xylem, which subsides when the tree comes into leaf, is the driving agent. There is a substantial literature on the growing and tapping of maple trees, and the reduction of the collected sap into sugar, to which the reader can refer for complete details of this process.
Landscaping with Maples
Maples for Warm or Cold Sites
The only truly tropical maple is Acer laurinum from Indonesia, Malaysia, and the Philippines. Species that grow in nearly tropical or subtropical localities include A. buergerianum ssp. ningpoense ,
A. calcaratum, A. campbellii ssp. sinense , A. caudatifolium , A. coriaceifolium , A. elegantulum , A. fabri , A. oblongum , A. oliverianum ssp. formosanum , A. paxii , A. sikkimense ssp. sikkimense , and A. tonkinense. A list of this length will surely surprise those who think that maples are native only to cold- or warm-temperate regions. Somewhat less tender but not entirely hardy are
Acer campbellii ssp. flabellatumcer , A. pentaphyllum , and A. rubescens. Any of these do well in USDA plant hardiness zone VII or above. In colder sites, Acer caudatum ssp. ukurunduense , A. ginnala , A. negundo , and A. spicatum tolerate the temperatures of zone II; A. pensylvanicum , A. platanoides , A. rubrum , A. saccharinum , and A. saccharum do well in zone III; and A. campestre, A. tataricum , and A. tegmentosum can be used in zone IV. Acer mandshuricum can also be used in zone IV, but it is a special case. It is very hardy, thriving in Finland, for example, but cannot stand the treacherous spring frosts that occur after leafing out. It seems to think that winter is over after the easing of the extreme cold. It also requires hot summers to ripen off the wood and cannot tolerate long warm autumns that extend into December. It would probably do well in the continental climate of Canada and the United States.
Maples for Wet or Very Dry Sites
Because maples are very accommodating plants, they cope very well with dryness or wetness throughout a large range.
Acer rubrum tolerates wet sites very well, and A. pycnanthum in Japan grows in very wet conditions. Many species have riverbanks, valleys, or rich bottomlands as their natural habitats. Acer saccharum
ssp. floridanum grows in wet woods, and A. rubrum var. drummondii from the southern United States grows in deep swamps.
Acer circinatum is occasionally seen in dry sites. The Mediterranean species, such as A. hyrcanum , A. monspessulanum , A. obtusifolium , A. opalus , A. sempervirens , and A. syriacum (syn.A. obtusifolium) survive well in hot and dry summers, although they benefit from mild and wet winters. < right="" image:=""> Acer sempervirens. Grafted young plant, collected in the wild on Crete.>