A Bouquet for Arbor Day
To celebrate Arbor Day in Kentucky, here is a spring bouquet for you.
[envira-gallery slug=”a-bouquet”]
flowers
Flowers, Pollen and Allergies
Is that tree causing your allergies? That pretty tree with the white flowers? That pine tree covering your car in green film? Nope. It’s the trees you don’t see that are getting you.
This is the height of allergy season. You can feel it in your sinuses and see it on your car windows. Huge amounts of pollen are flying through the air, seeking out female flowers with which to mate. There are many misconceptions about pollen, tree flowers and allergies.
In my experience, many people are confused about what trees cause allergies. The beautiful showy flowers of spring trees like black locust or flowering crab are not the cause of allergies. These flowers are designed to attract insects, hummingbirds and other pollinating animals. They do not toss their pollen into the air, but wait for animals to carry pollen from tree to tree.
It is the tree flowers we don’t notice that are the culprits. Oak, Osage-orange, hickory, and lots of other trees produce long male flowers called catkins that drop huge amounts of pollen into the air. You may not notice the flowers, but your respiratory system does.
Pine, spruce and other conifers don’t produce flowers, but they do toss huge amounts of pollen into the air. However, their pollen is so large that few people have problems with conifer allergies.
So, if you have to curse at a flower this spring, don’t pick on the pretty ones.
Bees on Bur Oak
For the last 10 days, I have watched an amazing phenomenon that I have never seen before. Oaks are wind pollinated. Occasionally we see insects visiting, but only casually. However, one bur oak that I keep an eye on has been abuzz with activity. Every day while the male flowers were open, there was a constant movement of bees. I saw several species, but only one was large enough to photograph readily. This large bee, about half the size of a honeybee, was abundant and working hard, with full pollen baskets.
What do you think? Have you ever seen this before? Comment below (Facebook) with your observations
A few other observation: The bees were not working other nearby bur oaks. There were lots of other trees and shrubs nearby with showier flowers but they were not as heavily visited and did not have the same bees.
And now the big question – are these bees robbing pollen, or are they actually pollinating this bur oak?
Early Spring Trees
You may feel we are in the throes of winter, but for many trees, it is already early spring. How can that be?
In the late summer, trees begin to enter a stage of deep sleep called dormancy. They don’t stop growing because it is cold, they stop growing because a combination of long nights and cold sets up a complex hormonal response. If you take a twig off a tree in late fall and bring it inside, giving it plenty of light, warmth and water, it will probably do nothing. It is not simply asleep, but dormant, and only one thing will wake it up – more cold.
By now, in most North Temperate regions, some trees have gotten enough cold to overcome dormancy. They are poised to begin growing as soon as the weather improved. Other trees are not ready yet – they need more cold to overcome the dormant state.
If you are a careful observer, you should begin to notice buds beginning to swell, bud scales changing color, and even a few trees beginning to show flower parts. These trees are ready for spring and only need a few warm days to begin growing. In my area, red maple, silver maple, and elms are ready to go.
If you don’t want to wait, try bringing some twigs inside. Set them in water like a flower arrangement, and see what happens over a few days. Some trees will do nothing – they are not yet ready and need more cold days. Oak, beech and hickory often require longer periods of cold. Other trees will pop in a few days.
Friday Tree Followup
This week’s Friday Tree was tricky. Some of you got it, and some of you were very close. The two reasonable guesses were Catalpa, Catalpa speciosa, or desert-willow, Chilopsis linearis. The flowers of both these trees are similar, and they are closely related, but they occupy very different habitats: catalpa is a midwestern tree of moist forest, while desert-willow is a shrub or small tree found on desert waterways in the American west.
This tree is Chitalpa, xChitalpa tashkentensis, a hybrid between to different genera of tree, Catalpa and Chilopsis. The one shown here is called “Morning Cloud” and genetic analysis shows that is Catalpa speciosa x Chilopsis linearis. Hybrids of two genera are extremely rare.
The hybrid was created by A. Russanov of the Botanic Garden of the Uzbek Academy of Sciences in Uzbekistan in 1964. However, the two parents are from the eastern US (Catalpa speciosa) and the western US (Chilopsis linearis).
The tree in these pictures is the only one I have seen in Kentucky. It has very peculiar leafing and flowering dates, leafing out in late May or early June and flowering from July to September.
An elegant old tree
There is a beautiful old catalpa tree at Ashland, in Lexington, KY, that has been loved by generations of visitors. I suspect it is the most photographed tree in the Bluegrass. A close look at the tree shows the great character that develops with age. Here is a slide show of the old tree.
Pollen cones of white pine
Conifers like eastern white pine, Pinus strobus, don’t produce flowers, but they can be very attractive in the spring when they show their cones. Here is a slide show of pollen cones, male cones that produce clouds of yellow pollen. Don’t worry, pine pollen rarely causes allergies.
Life cycle of buckeye
Ohio buckeye, Aesculus glabra, is a common tree in the Bluegrass and Midwest. Here is a slideshow of its life cycle. More photos will be added as time permits.
Time for Services
Serviceberry trees are blooming all over the Appalachians. Although other trees like birch and alder may flower earlier, the first showy flowers are serviceberries, coming a couple of weeks before the dogwood. The slopes of all the forested hollows in eastern Kentucky are dotted with these elegant, slender trees.
In the old days, before good roads and easy transportation, serviceberry flowers played an important cultural role. You see, when a person died in the winter, it wasn’t possible to hold a service and a burial. The ground was frozen solid, and a proper grave could not be dug. With deep snow and poor roads, it was difficult to travel from one holler to another.
Serviceberry blossoms provided the signal, more reliable than the calendar. The haze of white flowers in the hollows meant that the ground was thawing and it was time to go to funerals. The body in its yellow-poplar or chestnut casket, would be stored in the barn until the serviceberries bloomed.
That is, of course, how this tree got its name. It has lots of other names – the number of names of a tree is, I think, a measure of its usefulness. Sarvis is a variant of Serviceberry. Shad, or shadbush or shadblow was another set of names having to do with telling time – when the shadbush blooms, the shad are running in the creeks and it is time to go fishing. Pieberry or pietree, which I have only seen a few times, is an indication of something later in the calendar – the berries are delicious in jams or pies if you can beat the birds to the fruit. I have three serviceberries in front of my house, but if I wait long enough for the fruits to fully ripen, the birds get them first.
There are several species of serviceberry. Our common tree-sized serviceberry, Amelanchier arborea, common or downy serviceberry and Amelanchier laevis, Alleghany serviceberry, are difficult to tell apart except when the leaves are just breaking bud. Then, the leaves are downy, as the name suggests. There are several other less common species, but by far the most popular ornamental is the shrubby Canada serviceberry, Amelanchier canadensis. Although not native to Kentucky, it is abundant in states to the east.
Serviceberry flowers in the spring when the soil is thawed
Ripe fruit of Canadian serviceberry
Winter Sex: The Puzzling Case of Witchhazel
This is part of our ongoing series on tree sex.
Witchhazel is one of the most beautiful shrubs or small trees in forests throughout the temperate zone. It is easy to overlook in the summer, mixed in with lots of other shrubs and trees along creek banks and moist lower slopes of forests.
It is in the late fall and early winter that witchhazel stands out from its neighbors, and reveals its strange habits: witchhazel flowers in the winter. American witchhazel, Hamamelis virginiana, grows in eastern North America and flowers in late fall and early winter. Vernal witchhazel, also called Ozark witchhazel, is found from Missouri to Texas and flowers in late winter or early spring (vernal means ‘spring’). There are many ornamental witchazels, including the hybrid shown here, Hamamelis x intermedia ‘Arnold’s Promise’. Whatever their habitat or geographic origin, all of the witchhazels flower when other trees are still snoozing through the winter.
This would not be so odd, except that these are obviously insect-pollinated flowers. The long, bright-yellow petals, the presence of nectar producing a sweet smell and the stamens (pollen-bearing male bits) that are right next to the nectar source are all indicators of an insect pollinated flower.
For a long time, it was a mystery how a winter-flowering plant would get pollinated. A witchhazel that happens to flower on a slightly warm spring when honeybees are making their first flights in desperate search of food might get lucky. That is not a reliable way to reproduce.
It was the renowned naturalist Bernd Heinrich who realized that there was a group of owlet moths (family Noctuidae) called winter moths that are active on cold nights. These moths have a remarkable ability to heat themselves by using energy to shiver, raising their body temperatures by as much as 50 degrees in order to fly in search of food. It is a group of these moths that pollinate witch hazels. The moths that pollinate witchhazel are several species of Eupsilia known as sallows.
It would be easy to conclude that this is a case of coevolution – both organisms having evolved to depend on one another. This is probably not the case – Heinrich observed that these moths mostly feed on bleeding sap from injured trees. So, the tree is dependent on the moth, but the moth is probably not dependent on the tree.
So the next time you see a witchhazel in flower, remember that it is waiting for a shivering moth.
References:
Heinrich, Bernd. 1987a. “Thermoregulation by Winter-Flying Endothermic Moths.” Journal of Experimental Biology 127 (1): 313–32.
———. 1987b. “Thermoregulation in Winter Moths.” Sci. Am 277: 73–83.
———. 1998. The Trees in My Forest. Reprint. Harper Perennial.
