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Trees

Next Year’s Buds Already Formed

11-7-18 A. beech bud _U1A1228Because tree buds tend to swell and increase greatly in size in the spring, this is often the season when we first notice them and assume that this is when they are produced.  However, if you look in the axils of leaves on any deciduous tree right now, you will see full-size buds that were formed this summer.   These little packages of miniature leaves, branches and sometimes flowers, will remain on trees all winter, tightly closed and often protected from the elements by modified leaves called bud scales.  Come spring, when trees are once again taking up quantities of water, their buds will swell, scales will fall off (leaving bud scale scars), and tiny, pristine leaves or flowers will appear.  (Photo is of American beech, Fagus grandifolia, bud.)

Just a quick reminder that the NC Calendar ordering deadline is November 10th.

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Mystery Photo: Young Eastern Black Walnuts

7-6-18 black walnuts IMG_8342Congratulations to “Deb” – the first person to correctly identify the subject of the most recent Mystery Photo as young Eastern Black Walnuts!

Eastern Black Walnuts (Juglans nigra) produce abundant tiny male flowers on long, dangling, finger-like catkins. Female flowers, located on the same tree as male flowers, are fewer in number and are slightly larger. Being wind-pollinated, Black Walnut produces female flowers with stigmas (the top-most, pollen-receiving structures) which have a large surface area designed to catch pollen drifting in the wind. (These are the “rabbit ears.”) The stigmas often persist while the fruit matures  — they are barely visible on the left walnut in photo.

By September, the walnuts will have matured. They then fall to the ground where their outer husk slowly decays. The fruits are well-known for leaching chemicals into the soil that inhibit the growth of other plants, an interaction known as “allelopathy” (literally meaning “making your neighbor sick”).

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American Hophornbeam Fruiting

9-26-17 hophornbeam fruit 049A5466The fruits of the Hophornbeam tree (Ostrya virginiana), also known as Ironwood for its strong, hard wood, are drooping clusters of papery, bladder-like sacs each containing a nutlet. The “hop” portion of its name refers to the resemblance of these fruits to those of true hops that are used in the production of beer. Hornbeam refers to a related European tree whose wood was used to yoke oxen; therefore, its American counterpart wood was also used as a “beam” with which to yoke “horned” beasts of burden.

 


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

4-20-17 red maple male flowers IMG_2938

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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