If you were raised in the Christian religion, you've probably heard of frankincense and myrrh. But, do you know much about them, beyond being fragrant commodities as precious as gold?
Until today, I could not have described frankincense, myrrh, or citronella. But, by the time I was finished with my volunteer shift at the U of M Conservatory greenhouse I knew more about them.
However, I will have to wait for another time to actually see a myrrh tree. I'm not sure if the Conservatory has a myrrh tree. I do know myrrh is in the Burseraceae family, the same family as the frankincense tree. They are not in the myrtle family as the name would suggest. The myrtles (or Myrtaceae) are the gum trees of the Australasia, one which gives us citronella (see below).
Maintenance of small trees
The day's duties assigned to me were to provide general light maintenance to a group of small trees located in the desert and subtropical rooms of the greenhouse. Maintenance included pruning and making sure the trees were all properly supported with stakes, poles, and ties. I worked with several trees and plants, but I'll only highlight a few of them in today's blog post.
Frankincense tree, Boswelia sacra
This is a small bush-like tree, not more than a couple meters in height. It is native to the countries surrounding the Gulf of Adan (Yemen, Somalia), as you'd expect given the biblical references. The leaves are compound, with many leaflet on a petiole stalk. The tree is deciduous, losing its leaves every year. The green branches feature thin papery bark. When the bark is injured, thick latex-like sap exudes from the sore. For thousands of years people have collected the sap and dried it to form resin, which is then used for incense, or pressed for oil to use as perfume.
The scent of frankincense is said to have a woody scent, with a spicy undertone. The scent of myrrh is said to be woody with a undertone of citrus.
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| Frankincense tree, Boswelia sacra |
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| Old tree branch and piece of hose are used to support this green limb of the frankincense tree |
In the photo, I've used and old tree branch to prop up the frankincense tree. In doing so, I nicked the green bark which caused sap to ooze out. To prevent further injury I placed a short segment of rubber hose to cushion the branch as it rests against the support pole. Using an old tree branch as a support pole gives the tree a more natural appearance.
Hakea laurina, the pin-cushion hakea
This hakea tree is doing very well in the subtropical room. All it needed was a bit of pruning because it is crowding out the neighboring tree; they were originally planted too closely, now they are trying to escape each others shade.
This small hakea tree is native to Australia. It is popular with gardeners for its blossoms. In the wild it is threatened due to habitat loss to agriculture.
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| Pin-cushion hakea, Hakea laurina, with blossom buds |
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| Pin-cushion hakea blossom (photo by JJ Harrison (https://www.jjharrison.com.au/) |
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| Pin-cushion hakia |
In the myrtle family: the lemon-scented gum Corymbia citriodoria, maker of citronella
I didn't know this: citronella comes from the sap of this Australian gum tree. Citronella is used as a mosquito repellent and in some perfumes.
This small tree needed to be tied to the railing to prevent it from flopping over onto the ground. It has spent is entire life in the greenhouse being supported. It didn't develop the root structure to support the weight to which it has grown.
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| Lemon-scented gum, Corymbia citriodora (in the myrtle family Myrtaceae) |
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