An online resource based on the award-winning nature guide

Woody Plants

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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Distinguishing the Hornbeams

1-23-17-hophornbeam-img_5028There are two trees, both in the Birch family, which, due to the similarity of their common names, are occasionally mixed up with each other. One is known as American Hornbeam (Carpinus caroliniana) and the other as American or Eastern Hophornbeam (Ostrya virginiana). Due to the hardness of their wood, they also both go by the name Ironwood, adding to the confusion. A perfect example of when Linnaeus’s binomial system, which gives each species two scientific names, one of which is unique to each species, is helpful.

While the fruits and leaves of both species are superficially similar, their respective bark is very different. Carpinus caroliniana’s bark resembles flexed muscles (see   https://naturallycuriouswithmaryholland.wordpress.com/2012/10/30/american-hornbeam/ ), earning it yet another common name, Musclewood, while Ostrya virginiana’s bark (pictured)  has a “shreddy” appearance, with the bark broken into small, narrow plates which curve away from the trunk. Look for C. caroliniana in valleys and along streams, and O. virginiana on well-drained slopes and ridges.

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Partridgeberry Fruit

partridgeberry-049a1637Partridgeberry (the fruit is eaten by partridges, or ruffed grouse, as well as wild turkey, mice, foxes, skunks and deer) is a woody vine found creeping along the forest floor, often in large colonies. At this time of year there are bright red berries interspersed among the paired evergreen leaves. If you look closely at a berry, you will see two indentations at its tip. These are the result of the flowers’ unusual structure and the fruit’s development.

In late spring a pair of white flowers appears which share a set of sepals. Each small, fragrant flower has four white hairy petals that join to form a tube. The unusual aspect of these flowers is that they both must be pollinated to obtain a single berry. Each berry is the result of the fusion of the ovaries of the pollinated pair of white flowers. This fusion is what accounts for the two indentations on the surface of each fruit.

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Witch-hazel Cone Gall Aphids Laying Eggs

10-26-16-witch-hazel-gall-s20161017_5388At this time of year there is a species of aphid, Hormaphis hamamelidis, that is laying eggs on Witch-hazel branches. Next spring female aphids will hatch out of these eggs and begin feeding on newly-emerged Witch-hazel leaves. The aphids inject the leaf with a substance that causes the leaf to form a cone-shaped growth, or gall, around the insect, providing it with both food and shelter. The galls are hollow, and have openings extending out through the leaves’ lower surfaces. Within the galls the unmated female aphids produce 50 – 70 young. Eventually the galls fill with winged female aphids which emerge through the cone openings, disperse, and repeat the process. The third generation of aphids consists of both males and females which mate and lay their eggs on Witch-hazel. The aphids that hatch from these eggs create the conical galls found on Witch-hazel leaves.

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Abscission Layers Forming

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As the days grow shorter and the nights longer, cells near where a leaf’s stem joins a tree’s branch start to divide rapidly. This is the start of the creation of the corky layer of cells known as the abcission layer.

The annual growth of a tree ends with the formation of the abcission layer. This layer prevents the transport of materials such as carbohydrates from the leaf to the branch and it blocks the flow of minerals from the roots into the leaves. Chlorophyll, critical to the process of photosynthesis, breaks down with exposure to light and is replaced continually by the leaves during the summer. When the abcission layer forms, this is no longer possible.  The chlorophyll slowly breaks down and disappears, revealing the underlying xanthophylls (yellow pigments) and carotenoids (orange pigments) that the chlorophyll was masking. These pigments, in addition to the red pigments (anthocyanins) that are manufactured from sugars trapped in the leaf, provide us with our brilliant foliage.

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More Buds

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The previous “bud scale” post engaged readers to an extent that made me feel another post with additional buds to scrutinize would be welcome. Apologies to non-woody plant aficionados!

When identifying woody plants in winter, one takes advantage of everything a tree or shrub has to tell you: bud/branch arrangement (opposite/alternate), bark, silhouette and terminal buds. Buds are so revealing that they alone can immediately tell you what species you are seeking to identify. Is there one bud at the tip of each branch (willows) or multiple terminal buds (red oak)? Are there bud scales (no-witch hazel; yes- bigtooth aspen)? If so, what are their number (willows – one) and arrangement (overlapping, like shingles – red oak)? Are the buds red (striped maple), brown (witch hazel), yellow (bitternut hickory), green, or some combination of these colors? Are they pointed (bigtooth aspen) or rounded (willow)? Every species of tree has buds with a unique combination of these characteristics.  Now is the time to observe them, as some will soon start to open.

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