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Collecting Sugar Maple Seed

This article about collecting Sugar Maple seed was written by Barb Boysen, expressly for Maple Leaves Forever. The principles and methods described are applicable to other species of native maples. Without locally sourced seed that is properly collected, treated and stored, our restoration plans and our genetic heritage are at risk. Barb is the Co-ordinator of the Forest Gene Conservation Association in Peterborough.

Collecting Sugar Maple Seed

Early May – trees are covered in yellow flowers, potentially a bumper seed year.

Mid May 2006, leaves just starting to flush.

Sugar maple female flowers with seed starting to
form– note samara tips emerging Photo credit – Brian Swaile

Sugar maple samara, late June 2006 – not yet mature.

Mature sugar maple samaras, early October, 2006, Guelph – note yellow-brown wings
Photo credit – Sean Fox

Sugar Maple in mid October 2006, Peterborough.
Most leaves have fallen leaving behind the mature seed – a bumper crop.
Photo credit – Barb Boysen

Future generations of sugar maples are dependent on seed produced by today’s mature trees. Trees as young as 22 years can produce some seed but the better crops are produced by much older trees – and sugar maple can live for 400 years. In a heavy seed year millions of sugar maple seed can fall in one hectare of forest. As such, sugar maple regenerates very well on its own, and its tolerance to shade means young seedlings and saplings can subsist in the understorey and respond well when some disturbance creates more light. Under similar conditions, red oak for example, would die out – it and many other species require more light at a younger age to survive.

Sugar maple can also regenerate vegetatively, for example, sprouting from stumps or damaged stems. And individual trees of particular interest can be cloned by budding or grafting. But cloning also has the effect of narrowing the gene pool – not a good idea in any forest – rural or urban. The heavy crop years when most parent trees produce seed are responsible for most of our healthy, genetically diverse sugar maple forests. These bumper crops are produced on average every 4 to 7 years. In southern Ontario, 2006 was such a year following almost 5 years of little seed.

There is generally no lack of sugar maple in our forests, though our urban areas, and predominantly agricultural areas could use some help. However, sugar maple is better adapted to shaded, moist regeneration sites, not the usually exposed, extreme planting sites of old fields or urban streets and parks. As such any sugar maple plantings should be planned with care – choosing the moister sites, with more shade and definitely followed by tending to ensure they become well established.

But before you can plant a tree, you need to collect the seed – high quality, seed of known, locally-adapted seed sources.

If you are interested in collecting sugar maple seed, it helps to know how it all starts – with the flowers in early spring (mid April to mid May in Ontario).

Sugar maple flowers can be perfect – that is, have both male and female parts. But the flowers on one tree are mostly unisexual; either mostly male or mostly female. Females and males can be found at the top of the tree, but usually there are only males in the lower crown. Pollination is by wind.

The seed is a winged seed or samara – and comes in pairs with 2 seeds fused together; the wings hanging parallel to each other. (Parallel wings are diagnostic of sugar and its close relative black maple; the invasive exotic Norway maple has wings oriented horizontally).

After pollination, the female flowers set seed which then take approximately 16 weeks to mature. In late June almost full-sized seed can be seen. This is a good time to forecast the crop and decide if a good crop is developing. Light seed years do not well represent the full genetic diversity of the local stand, and often have poorer germination rates and produce less vigorous seedlings – not worth collecting.

Sugar (and black) maple seed matures in the fall, usually from late September to early October. At maturity the seed cavity will be completely filled with a bright green embryo (a plant in early stage of development) which consists of the radicle (the root), the cotyledons (first seed leaves) and the hypocotyl (stem between the root and the seed leaves). The wing will be yellowish-brown, and the seed coat will eventually turn brown as well.

The mature seed may stay on the tree for several weeks, sometimes after leaf fall, which is when seed can be collected more efficiently.

Plan your collection efforts once you have determined that the seed is:

  1. worth picking = there is a lot of seed on most maple trees in the area;
  2. mature = wings are yellow-brown and you‘ve cut several samples from the trees you are going to collect from, to make sure that at least one seed has a fully developed embryo that fills the seed cavity; and
  3. you plan to grow it or have a customer to sell it to.

Collection options:

  1. Hand pick from the ground or using ladders
  2. Spread tarps under the trees and collect after natural seed fall
  3. Spread tarps and collect seed that falls after flailing the branches with bamboo poles.

If you are planning to sell the seed, check with the buyer before you collect to see how much they want, what source they want, how they want it packaged and when they want it. Some buyers may want you to remove leaves, twigs, and other debris. If you can not ship or deliver the seed right away, spread out the seed in thin layers on trays or tarps in a COOL, DRY area. Overheating and excess moisture will kill the seed or cause it to mold.

Trays or burlap bags are often used. The bags should not be filled with more than about 40 litres per bag or the seed will start to overheat. Prepare 2 labels for each container and place one inside, for example in the bag, and securely attach the other one on the outside.

Minimum information to record on the label is the species, collection date, location of seed source, the amount and your contact information.

Remember – seed collectors have a tremendous influence on the genetic fitness and therefore the long term ecological, social & economic success of planted trees. Please collect wisely.

Collecting Sugar Maple Seed This article about collecting Sugar Maple seed was written by Barb Boysen, expressly for Maple Leaves Forever. The principles and methods described are applicable to

Maple Trees

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Red Maple

Red maple leaves and bark

The red maple is usually a medium-sized tree with a moderate growth rate. The bark is smooth and light gray on young- and intermediate-aged stems, while mature bark is dark gray and rough. Crushed twigs do not emit a rank odor as does the silver maple. Twigs are reddish and have rounded, oblong, vegetative buds. Floral buds are globose and conspicuous, since they are borne in clusters. Lower branches tend to sweep upward.

The species makes an excellent suburban or rural landscape tree in acid soil regions of the state. Numerous cultivars are available and are marketed based on fall color and habit. This tree has an acid soil requirement and is intolerant of wounding. With red maples, manganese deficiencies are common in neutral to alkaline soils.
Leaves: The leaves of the Red Maple are very roughly toothed with 3-5 shallow lobes. Most of the Red Maple leaves are a light or a pale green to a whitish. During Autumn, leaves turn a bright red or an bright orange.
Twigs: Most Red Maple twigs appear to be slender and glossy. At first the twigs are green but later in the year they turn a red.
Fruit: The dioecious, red flowers are borne in dense clusters and appear in March or April before the leaves; the buds turn a deep red sometime before they open. Male trees can be planted if you do not want fruit. Fruits have wings spreading at narrow angles and ripen in May or June. The fruit consists of pairs of winged seeds, or keys, 1/2—1 inch in length on long, drooping stems. Fruit color ranges from red to green, becoming tan when mature.
Bark: On a young Red Maple the bark can be smooth and gray. On older trees, bark can appear to be darker and rougher with peeling flakes.
Other Important Facts: The Red Maple is found mostly in Pennsylvania. Most Red Maples grow to a length of about 50 feet high.

Norway Maple

Norway maple leaves and bark

The Norway maple was one of the most popular street trees in the United States in the ‘60s and ‘70s. It originated in Europe where it is native from Norway to Switzerland. It is hardy, retains its leaves longer than the native maples, and endures the smoke, dust, and drought of the city, though it is susceptible to verticillium wilt and girdling roots.

Leaves: The Norway Maples leaves are very different than those of the Red Maple. These leaves are 5 lobed and 4-7 inches wide. A milky sap pours from the stalk if it is broken. One characteristic by which it can always be distinguished is the presence of milky sap in the leaf stalks. If pressed or twisted, the leaf stalks always yield a few drops of milky sap. Foliage color is bright green above and shiny beneath, except for the horticultural color variants that include wine, golden, and variegated forms. Fall foliage color is yellow for the green-foliaged forms.
Twigs:The Norway Maples twigs are a reddish-brown. Buds grow on the ends of the twigs. Buds are large (1/4 inch) and red or greenish-red with two to three pairs of bud scales; they are a sure means of identification in the winter. Buds are rounded rather than acute-tipped.
Fruit: In early spring, the yellow to chartruse flowers are arranged in 3-inch diameter clusters along the twigs. Flowers are borne in April or May. This maple has the most attractive flowers of all maples. Flowers are showy since they bloom before the foliage emerges. Fruit has horizontally spreading wings that mature in September or October.
Bark: On young trees the bark can appear to be light brown and smooth. As the trees get older the bark gets darker and rougher. The grayish-black bark is furrowed with shallow, narrow ridges forming a regular diamond pattern.

Other Important Facts: The Norway Maple is imported from Europe. This tree, like the Red Maple, can also reach a height of 50 feet. It is not similar to other maples because of the larger leaves, milky sap and horizontal winged fruit. Leaf shape very similar to sugar maple but more ornate. A milky sap appears when the leaf is broken off of stem at the petiole. This sap is not found in sugar maple leaves and distinguishes the two species.

Sugar Maple

Sugar maple leaves and bark

The tree attains a height of more than 100 feet and a diameter of 3 feet or more. It is generally a slow-growing tree. In the open, sugar maples have a symmetrical crown. It is extensively planted as a shade tree, although it is urban intolerant and should not be used in tree lawns.

Leaves: are simple, 5 lobed with very few large teeth, which are about 4″ wide. The sinuses (division between the lobes) are rounded. The leaves are also a bright green towards the top,andpale green down to the bottom.These leaves turn bright yellow, orange or red in the fall.
Twigs: are a reddish-brown and go to a light brown. The twigs are smooth (glabrous) and reddish-brown in color. The winter buds are smaller than Norway maple and sharp-pointed with six to 10 pairs of scales.
Fruit: The flowers are yellowish-green, on long stalks, and appear with the leaves in April. Male and female flower clusters appear on the same tree. The fruit, which ripens in September, consists of a two-winged key. The two wings are nearly parallel, about 1 inch in length.
Bark: gray brown, smooth on young trunks, older trunks fissured with long, and irregular flakes. Bark is variable in this species. It is usually thin, smooth and gray on young trees, becoming thicker, darker and deeply furrowed into vertical, occasionally scaly ridges.

Differences:
The way to tell Red Maple and Sugar Maple apart is by the bark. The real difference is that the Red Maple has lighter and smoother bark then the Sugar Maple. Also the Red Maple has a bitter sap as compared to the Sugar Maple.

Silver Maple

Acer saccharinum (dasycarpum)

Silver maple leaves and bark

The silver or soft maple is most common on moist land and along streams. It attains heights of 100 feet or more and diameters over 3 feet. It usually has a short trunk which divides into a number of large, ascending limbs. These again subdivide, and small branches droop but turn upward at the tips. The silver maple grows rapidly and has widely been planted as a shade tree. The urban-tolerance of the silver maple makes it the longest-lived of the maples in urban settings.

The wood is soft, weak, even textured, rather brittle, easily worked, and decays readily when exposed to the elements.

Leaves Leaves are 3 to 6 inches long, opposite, simple, and palmately 5-lobed. Leaves are lobed more than half way to midrib. Margins are irregularly double-toothed. The leaf surfaces are glabrous, light green above and white to silvery below, giving it the common name “silver maple.” Fall coloring is green to yellow-brown, and is not striking.
Twigs: The buds are rounded, red or reddish-brown, blunt-pointed, and generally like those of the red maple. Clusters of globose floral buds are also present on silver maple. Crushed twigs emit a rank odor.
Fruit: The flowers appear in February or March, before the leaves, in dense clusters and are of a greenish-yellow or reddish-yellow color. This may be the first native tree to flower, although the flowers are not showy. Fruits have divergent and curved wings that mature in May or June. It consists of a pair of winged seeds, or key, with wings 1—2 inches long on slender, flexible stems about an inch long. Fruit can be a litter problem, since they are borne in great numbers.
Bark The gray-brown bark is smooth on young trees, later developing irregular furrows with thin, gray, scaly plates.

Black Maple

Black maple leaves and bark

The black maple is a large, deciduous tree 60 to 80 ft in height with a dense, rounded crown and a straight trunk up to 4 ft in diameter. It is very similar to the sugar maple, with a few distinguishing characteristics: the leaves are usually palmately 3-lobed with hairy lower leaf surfaces, the leaf blades are thicker and characterisically drooping at the sides, twigs are orange-brown and the bark is almost black and more deeply furrowed.

Leaves: The leaves are simple, opposite, with a few coarse teeth along the margins, dark green on the upper surface and yellowish-green below. The fall color is yellow or brownish-yellow, sometimes red, but less so than the sugar maple. The 3 to 5-inch petioles often have leaf-like stipules at the base which obscure the lateral buds.
Fruit
: Clusters of small, yellow flowers are produced in May at the base of newly-emerging leaves. The 0.5 to 1-inch-long winged fruits are produced in pairs. They mature and dry in late summer, sometimes separating when shed, leaving the hairy stalk on the tree.
Twigs: Winter buds are egg-shaped, with pointed tips and hairy, overlapping reddish-brown scales.
Bark: The bark of black maples is dark gray with deeply furrowed, irregular ridges. The bark is darker and more deeply furrowed than that of the sugar maple.

This page describes how to identify red maple, norway maple, sugar maple, silver maple, and black maple trees. Both leaf and bark are shown.