maple, rock maple)
maple (Acer saccharum) is the most abundant of the seven maple
species found in New York State, and is common throughout New England,
the Lake States, Mid-Atlantic states, and several Canadian provinces.
Its historical and economical importance, both in the production of
maple syrup and as a timber species, has earned sugar maple its status
as the official state tree of New York. The sugar maple leaf on
the Canadian flag is evidence of this species' importance in Canada.
optimal growing conditions, sugar maple can attain heights in excess
of 100 feet. The largest reported individual was found near Bethany,
West Virginia; it had a diameter of 5.6 feet, a crown spread of 75 feet,
and a height of 110 feet. Most mature trees, however, range from 70
to 90 feet in height and have diameters at breast height (4.5 feet above
the ground) commonly measuring from 2 to 3 feet. Trees grown in the
open have trunks that branch near the ground, forming crowns that spread
60 to 80 feet. In contrast, those found in shaded forest conditions
normally develop clear, straight boles and narrow crowns.
The leaves of sugar
maple are simple (single) and like the buds are in an opposite arrangement
on the twigs (Figure 1). They are usually five-lobed although
certain trees may possess leaves with three, four, or five lobes. Leaves
are dark green on the top surface and paler underneath. They are generally
smooth on both sides, although the veins underneath may be slightly
hairy. Leaves typically measure from 3 to 5 inches long. The
margins between lobes are shallow and smooth, which distinguishes them
from leaves of the similar-looking red maple (Acer rubrum), which
has serrated lobe margins. Another difference in the leaves is
the "U-shaped" connections between lobes of sugar maple leaves
versus the "V-shaped" connections of red maple.
Twigs are fairly
slender, a shiny reddish-brown color, and covered with lenticels (small
openings in the bark, Figure 1d). The pith (inside core) of the
twig is white. Buds are narrow, sharply pointed, and brown. The terminal
bud may be larger (0.25 to 0.5 inch) than the lateral
buds (0.10 to 0.25 inch).
The bark on young
trees is dark gray, but as the tree ages the bark develops rough vertical
grooves and ridges (fissures) and may appear dark brown. On mature
trees, the bark typically appears to have long plates that peel along
the side edge. The bark on mature red maple trees typically has
more narrow plates that peel from the top or bottom edge.
The flowers of sugar
maple are greenish yellow with long stalks (pedicels) appearing in drooping
clusters 1 to 2.5 inches long. Sugar maple is monoecious; that is, it
has female (staminate) and male (pistillate) flowers on the same plant
(Figure 1b and Figure lc). The fruit, a double samara, has a
characteristic winged shape (Figure le).
maple is one of 148 maple species found in the Northern Hemisphere,
which includes about 90 native and introduced species in the United
States. The range of sugar maple in North America extends from Nova
Scotia and Quebec at its northern edge, west to Ontario, southeastern
Manitoba, and western Minnesota, south to southern Missouri, and east
to Tennessee and northern Georgia (Figure 2). Sugar maple is
most common in New England and the Great Lakes states as well as Ohio,
Pennsylvania, and New York.
temperatures within the geographic range of sugar maple have average
January temperatures from 0 to 50° F and average July temperatures from
60 to 80° F. Maximum temperatures in the summer months range from 90
to 100° F, while winter minima vary from -40 to +20° F. Annual precipitation
throughout the geographical range averages 20 to 50 inches of rain,
plus from 1 to 150 inches of snow. In unusually wet years in the southern
reaches of this broad range total annual rain in excess of 80 inches
has been recorded.
The first killing
frost usually occurs between September 1 and November 10 and the last
from March 20 to June 15, depending on latitude and elevation. Thus
average growing seasons are from 80 to 260 days.
maple can survive in a wide variety of soil types, but for maximum tree
growth and sap production, soils should be deep, moist, and well drained
with medium or fine textures. In the Northeast, such soils are common
along glacial tills and benches. Areas generally not favorable to sugar
maple establishment include swamps, dry sandy ridges, and thin rocky
soils. The pH of soils supporting sugar maple ranges from 3.7 (strongly
acidic) to 7.3 (slightly alkaline), but the species is most commonly
found on soils with a pH of 5.5 to 7.3.
by sugar maple often produce a heavy leaf litter. Through the
nutrients present in sugar maple leaves, the decaying litter can gradually
have an influence on soil pH and nutrient status. Sugar maple
leaves contain about 1.8% calcium, 0.8% potassium, 0.1% phosphorus,
and 0.7% nitrogen based on their dry weight.
Over the full range
of soils where sugar maple occurs, it may be expected to reach a height
at age 50 of between 40 and 80 feet. This relationship between
height and a standard base age is known by foresters as site index.
However, site index has limits in utility for shade tolerant species
such as sugar maple that can remain suppressed as juveniles in the understory.
In these cases, site index values would underestimate the potential
productivity of the site.
of sugar maple are usually fully expanded three to four weeks after
the leaf buds begin to swell in the spring. The flowers emerge soon
after the leaves and are in full bloom within a week. Normally, a single
tree will produce both perfect (those containing both male and
female parts) and imperfect (those containing either male or
female parts) flowers. The ratio of male to female flowers is rarely
less than ten to one and is usually about fifty to one. There is a noticeable
localization of female flowers on certain areas of a tree crown.
The flowers are
pollinated by bees. Fruits that result from flower pollination usually
mature in about 10 to 12 weeks and become ripe in September or October.
The double samara fruit is characteristic of sugar maple, but usually
only one seed is viable. The samaras fall about two weeks after ripening,
which is approximately the same time the tree suspends its annual height
growth. Birds, squirrels, and other rodents usually consume only a negligible
amount of the seeds.
The minimum seed-bearing
age for sugar maple is about thirty years. After this age some seed
is produced every year, but massive quantities of viable seed are produced
cyclically, usually at two to five-year intervals depending on climatic
conditions. During these good seed years, trees are loaded with flowers,
which gives them a yellowish cast when seen from a distance. The seeds
are relatively heavy (average clean weight of 6,100 seeds per pound),
but the winged shape of the samaras provides for wide dispersal by wind
and blowing over snow.
The large quantities
of seed produced in good years normally result in many seedlings. Seeds
usually germinate in the spring following their autumn dispersal. In
addition, sugar maple has a strong tendency to sprout in response to
fire, cutting, disease, or physiological disorders. Stump sprouts are
an important means of vegetative (asexual) reproduction in many hardwood
forest stands. For example, the Ice
Storm of January 1998 broke crowns from many sugar maple trees throughout
the northeastern United States and Canada. Some of these sugar
maples will be able to resprout and ultimately regain their original
vigor, but others will have been so badly damaged they will ultimately
regeneration of a forest should be a major concern for any woodland
owner who is planning to harvest trees. In the case of sugar maple,
natural regeneration through seed establishment and prolific sprouting
is generally successful in replenishing the amount of growing stock
in a stand even after a fairly heavy cutting. Eastern forests can usually
be regenerated naturally, without the need to plant seedlings.
However, this involves careful planning, consideration of factors such
as interfering vegetation and deer browsing, and is best accomplished
in consultation with a professional forester. In New York, contact
professional foresters through the NYS
Department of Environmental Conservation, the New
York Institute of Consulting Foresters, or Certified Foresters in
the Society of American Foresters.
Once the seedlings
are established, frequent browsing by white-tailed deer (Odocoileus
virginianus) can be a problem. Sugar maple seedlings can survive
heavy browsing for many years, but they will most likely become stunted
and deformed. Such selective removal through browsing by deer and other
wildlife can cause significant changes in the composition of hardwood
The annual initiation
of height and radial growth in sugar maple usually corresponds with
leaf emergence. Depending upon location and local weather patterns,
height growth is usually completed in about 15 weeks; radial growth
normally ceases in 14 to 17 weeks following initiation.
The root system
of sugar maple in good soils is deep and branching. Natural root grafts
are common. The seasonal periodicity of root growth is independent of
aerial growth and often continues into the winter months if the soil
remains unfrozen. Over half of the root growth for any given year, however,
occurs during the same period as height and radial growth.
The growth rate
and crown form of sugar maple are largely dependent on the origin of
the saplings, as well as environmental factors. Saplings originating
from sprouts tend to grow faster than those from seeds or even planted
seedlings. The latter two, however, usually produce a healthier and
better-formed mature tree. Sprouts from stumps with diameters of less
than 2 inches are less likely to develop decay than those from larger
stumps or multiple sprouts.
Sugar maple trees
average about 1 foot of height growth and 0.2 inch of diameter growth
annually for the first 30 to 40 years. Hence a 30-year-old tree might
be 6 to 8 inches in diameter and 30 to 35 feet in height. After about
140 to 150 years, height growth ceases and radial growth slows greatly.
Although rare, old-growth sugar maple stands can average 300 to 400
years in age; individual trees range from 70 to 110 feet tall with diameters
at breast height of 20 to 36 inches.
Diseases, Insects, and Injuries
whether in a forest or urban setting, are constantly exposed to many
damaging agents during their lifetime. Various diseases, numerous crawling
and flying insects, and physical injury can all cause the decline of
Sugar maple is
susceptible to various disease organisms at all stages of development.
Rhixoctonia solani and Sclerotium bataticola attack nursery
seedlings; the latter damages the pith. As the trees age, they are subject
to various foliage and stem diseases. Some of the more common foliage
diseases include anthracnose (Gloeosporium apocryptum), which
forms necrotic (dead) areas on the leaves. These are sometimes circular
in shape and may be of various sizes; they turn brown, purple, or black
as the disease progresses. Tar spot (caused by Rhytisma acerinum)
is the name commonly given to a foliage disturbance in sugar maple
that starts with small black dots on the leaves, which eventually combine
to form large, black, thickened areas.
Most stem diseases
exhibit cankers or galls. Cankers are sunken portions of the trunk or
woody branches that often have a callus-like buildup of bark around
the edges. Two common cankers of sugar maple are caused by the fungi
Nectria and Eutypella. Galls are obvious out
growths on the main trunk of a tree, usually within 8 feet of the ground.
diseases that can injure sugar maple are usually caused by fungi entering
the stem through wounds in the trunk or branches. Most vascular diseases
are not fatal, but they can produce toxic substances that cause decay.
For example, trunk rots are caused by fungi that enter the tree through
frost cracks, dead branches, and stubs and less frequently through the
Sugar maple is relatively
free from diseases of the root system, although they sometimes attack
otherwise weakened or diseased trees. For example, verticillium wilt
(V. alboatrum) is a common killer of shade trees, but it is less
damaging to sugar maple than to Norway maple (Acer platanoides).
This disease infects the roots and causes green streaks in the wood.
Stains are another broad group of diseases affecting both hardwood (broadleaf)
and softwood (conifer) trees. They discolor the wood, reducing its commercial
Insect predation of sugar maple is usually not a serious problem,
although in some years under certain conditions insects can initiate
significant growth decline or mortality. In periodic cases of unusually
large insect population buildups, such as with gypsy moth (Lymantria
dispar) in the Northeast, however, insect damage may be serious.
Other insect species that commonly attack sugar maple include the fall
webworm (Hyphantria cunea), saddled prominent (Heterocampa
guttivitta), sugar maple borer (Synanthedon acerni) pear
thrips (Taeniothrips inconsequens), forest tent caterpillar
(Malacosoma disstria), maple trumpet skeletonizer (Epinotia
aceriella), maple leaf cutter (Paraclemensia acerifoliella),
and maple petiole borer (Caulocampus acericaulis). As implied
by the names of these pests, most insect-related problems in sugar maple
involve the leaves.
Sugar maple is very sensitive to high sodium levels in the soil.
Hence it can sustain major injury from salt added to road surfaces to
melt winter ice and snow. The use of salt in the winter is a common
practice throughout much of New York State and New England. Affected
trees are found primarily along roads, although in extreme cases water
drainage from roads into maple stands has caused extensive damage. Salt
enters the roots and accumulates throughout the tree. When soil moisture
levels decrease, the high salt concentration in the tissues causes the
death of many twigs. Therefore, salt damage becomes obvious following
long dry periods during the summer.
For more information
on Cornell Extension research on sugar maple diseases, click
management of any forest must begin with specific goals. Stands of sugar
maple can be managed to produce sap for syrup and wood for a variety
of products. Both of these alternatives can be beneficial to wildlife
by providing cover, browse, and nesting sites.
A sugar maple stand
managed for the production of maple sap is commonly referred to as a
sugar bush or sugar grove. The ideal tree in such a stand has special
genetically and environmentally controlled characteristics that provide
for a large amount of sweet sap to be produced annually; it can then
be gathered and evaporated efficiently. Most important of these characteristics
is a large crown in which many leaves are exposed to direct sunlight.
Sap flow is also enhanced by large stem diameters, which develop from
wide, deep crowns. Hence open-grown trees with wide crowns favor high
sap production rates. Therefore, in a closed stand heavy thinning is
normally recommended to simulate an open-grown environment. Before
completing abrupt changes in your forest through timber or firewood
harvests, it's best to consult with a professional forester.
Growing trees for
high-quality timber requires a different type of stand than that desired
for maximum syrup production. A good sawtimber stand has trees with
tall, straight stems and no branching below the growing crown. Historically,
forest management in hardwood forests in the Northeast has favored uneven-aged
stands and natural regeneration. As markets for fuelwood and other uses
for pole-size (4 to 12 inches in diameter at breast height) trees develop,
thinning of young stands becomes increasingly attractive to the forest
landowner. Thinning a stand, practiced at various stages of development,
involves removing poorly formed trees, as well as dead and diseased
trees, to promote the growth of healthy, well formed members of the
stand. Hence the goal for dense sugar maple stands is to remove as many
inferior trees as possible without promoting open-grown characteristics
in the remaining trees.
Sugar maple is a
very prolific seed producer, and most stands regenerate naturally. Nursery
seedlings are sometimes planted to establish a stand for future maple
syrup production or to establish individual trees for ornamental use.
Normal transplanting procedures should be followed, and water, fertilization,
and weed control should be provided as needed. Transplanting seedlings
from the wild, however, is much more involved because it requires locating
good seedlings (open-grown trees 4 to 7 feet in height) and takes about
a year of preparation time (trenching is required 9 to 12 months before
transplanting to develop an adequate root ball). In any case, the root
ball should be planted intact slightly deeper than in its original location.
Extra watering and fertilizing may also be necessary. For optimal production,
trees should be spaced at 35-foot intervals in rows placed 35 feet apart.
This site also contains
information about management and production
for experienced syrup producers, beginners or hobbyists, and the general
derived from sugar maple trees are common in house holds throughout
the country. The maple syrup and sugar industry is an important part
of many agricultural economies in the Northeast. The earliest written
accounts of maple sugaring were made in the early 1600s by European
explorers who observed American Indians gathering maple sap. Today,
sugar maple stands and roadside trees provide private landowners with
an annual cash crop as well as a rewarding hobby (see the Cornell
Sugar maple has
long been valued as a hardwood timber species because of the wood's
hardness and resistance to shock. In early America, the wood was used
for a variety of household items, including rolling pins, scoops, apple
grinders, and cheese presses. Today its uses include lumber for general
construction, flooring, furniture, cabinet work, and woodenware. The
high density of sugar maple wood makes it a popular fuel for home heating.
Sugar maple is a
popular ornamental tree because of its tolerance to shade, spreading
form, and brilliant autumn foliage. Of the large number of maples available
for residential plantings, however, sugar maple is chosen less often
than Norway maple, red maple, and silver maple (Acer saccharinum).
Nonetheless, sugar maple has been widely planted in the eastern United
States, especially as a roadside tree.
Luzadis, V.A. and E.R. Gossett. 1996. Sugar Maple.
Pages 157-166. Forest Trees of the Northeast, edited by James
P. Lassoie, Valerie A. Luzadis, and Deborah W. Grover. Cooperative Extension
Bulletin 235. Cornell Media
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