An online resource based on the award-winning nature guide

Tree Flowers

Striped Maples Flowering

6-2-17 striped maple flowers 027Striped Maple (Acer pensylvanicum), named after the vertical white streaks on its bark,  is often associated with Moose and White-tailed Deer, both of which feed on its bark. In some places it goes by the name “Moosewood” for this very reason. The shape of its leaves give it another common name, “Goosefoot Maple.” In the spring when Striped Maples are nearly in full leaf, bright yellow bell-shaped flowers appear on long, pendulous strings, or racemes. (The flower stalks of the similar Mountain Maple also materialize after the leaves have matured, but these flower clusters are upright, held above the surrounding leaves.)

Striped Maples have the unusual ability to change sexes repeatedly over their lifetime (as does Jack-in-the-Pulpit), a phenomenon called gender diphasy. Among five study populations located in New Jersey, approximately one in four trees exhibited a change in the sex of its flowers between flowering seasons. The flowers of most Striped Maples are predominantly male. If changes occur in the canopy and new conditions seem favorable, a predominantly male tree can become predominantly female (and vice versa, if conditions deteriorate). Size, injury, and carbohydrate reserves are thought to impact the frequency and direction of gender change. Another unusual trait of Striped Maples is that the final sex of a flower is determined within one month of flowering, in contrast to most woody perennials which set buds the previous year.

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White Ash Flowering

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In 1935 Walter Rogers wrote a book on tree flowers (Tree Flowers of Forest, Park and Street) in which he described White Ash (Fraxinus americana) in the following words. “The Ashes are important trees with interesting features of form and foliage, but their flowers are among the least interesting.” I am of a different opinion, at least regarding White Ash’s male, or staminate, flowers.

White Ash is dioecius – individual trees have all male or all female flowers. Just before and as the tree is leafing out, the flower buds, located on the shoots of the previous season, begin to open. Male flowers are more noticeable than female flowers, partly because of the size of their clusters — there are between 200 and 300 flowers in each cluster – and their vibrant color (which resembles the fall color of some White Ash leaves). Being wind-pollinated, White Ash’s flowers lack petals as they would impede pollination. The stamens are a purplish-red, raspberry-like color until they mature, at which time the pollen’s yellow color is predominant.  The flowers are soon hidden by emerging leaves, so now is the time to see if you agree with Mr. Rogers!

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Bigtooth Aspen Male Catkins

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Aspens, cottonwoods, poplars – all are names for certain species of trees in the genus Populus. These trees, as well as birch, hickory, oak and willow trees, produce their flowers on spikes called catkins. Telling the catkins of these trees from one another is challenging, to say the least, yet some of NC’s readers correctly identified the catkins in the photograph as those of Bigtooth Aspen, Populus grandidentata. This tree blooms for one to two weeks in the spring and its mature male catkins open and extend to two to four inches in length. The wind, as opposed to insects, disperses the light, fluffy yellow pollen as the catkins dangle in the breeze. Some of the pollen remains intact even after the tree has shed its spent catkins onto the ground.

Because Bigtooth Aspen, and most species of Populus, are dioecious (male and female flowers develop on separate trees), there are only male flowers in this photo and beneath this tree. After fertilization, female flowers remain on the tree and form capsules which contain several small seeds embedded in tufts of fine, white hair. They will fill the air in several weeks looking like bits of floating cotton.

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Red Maples In Bloom

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Red Maples (Acer rubrum) are celebrated in the fall for their vibrant colors, but they produce equally vibrant reds and yellows in early spring when they are flowering. Most Red Maples have dense clusters of either male flowers or female flowers (dioecious), although some have both male and female flowers (monoecious). Under certain conditions, a Red Maple tree can sometimes switch from male to female, male to both male and female (hermaphroditic), and hermaphroditic to female.

The showier male, or staminate, flowers contain between four and twelve stamens, with long, slender filaments and red (young) or yellow (mature) anthers at their tips. Both red sepals and petals can be seen at the base of the stamens.  A staminate Red Maple in full bloom is a blaze of gold and red. (Photo: mature staminate Red Maple flowers)

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Witch Hazel Flowering

witch-hazel-20160917_0860Witch Hazel (Hamamelis virginiana) is nature’s final fanfare of the fall. As colorful fall foliage begins to disappear, the yellow strap-like petals of Witch Hazel’s fragrant flowers brighten denuded woods. This year, with a somewhat late peak foliage, they are both providing brilliant colors to the landscape at the same time.

Witch Hazel flowers are pollinated by moths that are still active this late in the season, and develop into small, hard capsules that remain dormant throughout the winter. During the following summer, these capsules develop to the point where they expel two shiny black seeds 10 to 20 feet away from the tree. The seeds take another year to germinate, making the length of time from flowering to germination approximately two years.

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Red Squirrels & Sugar Maples

2-20-15 red squirrel2 IMG_7851We’re approaching what is often a very stressful time of year for many animals, including red squirrels. In the fall they feed on all kinds of conifer seeds, mushrooms, insects, nuts and the many fruits and berries that are available. They also have caches of cones, which they turn to once there is a scarcity of food elsewhere.

Once these caches are used up, usually by late winter or early spring, red squirrels turn to sugar maples for nutrients. Their timing is perfect, for this is when sap is starting to be drawn up from the roots of trees. Red squirrels are known to harvest this sap by making single bites into the tree with their incisors. These bites go deep enough to tap into the tree’s xylem tissue, which is where the sap is flowing. The puncture causes the sap to flow out of the tree, but the squirrel delays its gratification. It leaves and returns later to lick up the sugary residue that remains on the branch after most of the water has evaporated from the sap.

Not only do red squirrels help themselves to sugar maple sap, but they have developed a taste for the buds, and later in the spring, the flowers, of both red and sugar maples. Red squirrels are not the only culprits – gray squirrels and flying squirrels also make short work of buds and flowers from these trees.

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Witch Hazel Flowering and Dispersing Last Year’s Seeds

10-11-13  witch hazel flower and fruits 055Witch Hazel (Hamamelis virginiana) is nature’s final fanfare of the fall. As colorful fall foliage disappears, the yellow strap-like petals of Witch Hazel’s fragrant flowers brighten denuded woods. These flowers are pollinated by moths that are still active this late in the season, and develop into small, hard capsules that remain dormant throughout the winter. During the following summer, these capsules develop to the point where they expel two shiny black seeds 10 to 20 feet away from the tree. The seeds take another year to germinate, making the length of time from flowering to germination approximately two years. (In photo, the yellowish-tan capsules were formed this summer, and the one brown, year-old capsule has opened and dispersed its seeds.)

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