After a very long hiatus, the Central Park Flora Blog is back!
Daniel and I have begun the 2016 collecting season and we are very excited about it. This year will be challenging. We have a wonderful collection so far, many common species and many not so common. This year, we will have to search very carefully for any species we have missed. But we are looking forward to the challenge.
Since the weather has not warmed up much and things are moving along slowly, I thought I'd start with a look at buds. An important structure for the plants and a good character we can use to identify species in winter. Looking at them closely reveals beauty that is often overlooked.
There are two types of buds - leaf buds (also called vegetative buds) and flower buds. Both are embryonic structures that give rise to either leaves or flowers. Buds on woody species have protective coverings called scales. Annuals and herbaceous perennials generally have naked buds. This post is looking at woody species. Flower buds develop and open at different times for different species. The ones we see now are early-blooming species. As spring and summer progresses, keep your eye out for flower buds that will open later in the season.
As we will see from these photos, buds are not only very beautiful, but they are unique to each species and serve and as a good identification character. There are so many to choose from. So here, in no particular order, is a sampling of what you can find in our parks at this time of year.
One of our first trees to flower each spring is the elm. The photo below shows the vegetative buds and the flowers of the American elm, Ulmus americana. I took this photograph too late to show you the flower buds, but aren't those flowers beautiful! The flowers will be fertilized and producing fruit before the leaves come out, as you can see in the second photograph (which I took last year). American elm seeds have hairs along the edges, distinguishing it from other elm species. The bud scales are reddish brown and darker along the margins. The terminal bud (the one at the tip of the stem) is angled at about 45 degrees.
The red oak, Quercus rubra, has a cluster of several buds at the tip of the stem. This is a feature common to all the oaks. Red oak has these lovely chestnut-brown buds, sharp-pointed with hairs along the margin of the scales. This is a common oak in Central Park as well as in other parks around the City.
Carya cordiformis, the bitternut hickory, is easily recognized in the winter by its buds. The bud scales are valvate, that is, they meet along their margins and do not overlap. The buds are sulphur-yellow. No other tree in our area has buds of this color. This seems to be the only hickory that is reproducing on its own in Central Park. In fact, it does very well and can be found throughout the woodlands. The seeds are bitter and the squirrels do not like them.
I first spot Sassafras albidum in the winter by its green stems, one of the few species to have this feature. Examination of the buds will confirm the identification of this species.
The flower bud in sassafras is distinctive from the vegetative bud. It is much more plump. The green scales are reddish towards the tip. The flower buds are the terminal buds and the vegetative buds are all lateral and much smaller. The sassafras is often found along woodland edges and in clearings where there is sufficient sunlight. When it leafs out, take a sniff, the leaves have a terrific fragrance!
Ginkgo biloba, the Maidenhair tree, has short stout axial shoots. These shoots have no internodes which make them very short. A node is the location where leaves or shoots emerge. Internodes are the spaces between two nodes. In the image below, you can see this year's bud - the structure that looks like a brown cap, made of overlapping scales. Beneath the bud is a ring of leaf scars, the half-moon shaped structure with two spots in it. Leaf scars are structures that remain where leaves used to be when they fell off in autumn. The two spots in this scar are called vascular bundle traces and show where vascular tissue, xylem and phloem, took water and nutrients into outhe leaves. The shape of the scar and the number and pattern of vascular bundles are unique to each species and are used in conjunction with buds to identify woody species in winter. You can see in the case of the Ginkgo, for each year, a ring of leaf scars is left and there is no space between them, they just pile one on top of another, no internodes.
Like the American elm, our native spicebush, Lindera benzoin produces its flowers before the leaves emerge. Small clusters of yellow flowers are out now and the tender, green and very fragrant leaves are only now emerging from the leaf buds. The flowers will eventually become the fruit, an oval drupe (stony pit surrounded by fleshy pulp). By September, the fruit will be a beautiful scarlet. Spicebush is an understory shrub of moist woods.
Emerging simultaneously are the leaves and the flowers of this buckeye species, Aesculus sp. You can see the leaves, still bronze, emerging below the buds of the inflorescences (clusters of flowers). Buckeyes have been planted in Central Park in the last ten years. This one is probably red buckeye, Aesculus pavia. It's European cousin, the horsechestnut (Aesculus hippocastanum) is more common in the park and around the city.
The London Plane, Platanus x acerifolia also has the leaves and inflorescences emerging at the same time. The globose (spherical) structures are the not-yet-mature flowers. The male and female flowers look similar but are carried on separate peduncles (flower stems). If you are able to zoom in on this photo, take a look at the beautiful pubescence (hairs) on the young leaves and the bud scales.
Speaking of pubescence, look at the stem and buds of Rhus typhina, the staghorn sumac; easily distinguished from the other sumacs by the dense velvety hairs on the stem and buds. The sumacs reproduce nicely in sunny edges of the woodlands and they give us fantastic fall color. Sumacs are in the same family as poison ivy, mangoes and cashews.
One more for the fuzzy collection, Amelanchier sp. Serviceberry is a wonderful early blooming native shrub. The flowers are fragrant and very beautiful, but don't forget to look at the other parts of the plant, they are just as beautiful in their own ways.
By this time, all the red maple flower buds are gone. This is a very early flowering tree for us, with spectacularly red buds. But fear not, you can still enjoy the color and beauty of the red maple since they are still in fruit! The first photo below is one I took last year of the flower buds. The second is a recent photo showing the double samaras forming on a red maple, with the stigmas still present. They are the smallest samaras of our maples and the only ones that are red. But don't wait too long to go and see them, they do not persist all season!