Elisabeth C. Miller Library

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Plant Answer Line Question

Keywords: Zelkova, Xylosma, Thujopsis, Taxodium, Tamarix, Poa, Pennisetum, Casuarina, Baccharis, Festuca, Juglans, Alnus, Palms, Allergies

What could cause sinus allergy symptoms every December?


According to Thomas Ogren's book, Allergy Free Gardening , the genera Alnus, Baccharis, Casuarina, Festuca, Pennisetum, Juglans, Poa, Tamarix, Taxodium, Thujopsis, Xylosma, Zelkova, and palm trees all produce pollen during December.

(Source: Ogren, T.L., Allergy-Free Gardening: The revolutionary guide to healthy landscaping , 2000, pp.262-265)

Also check out Allergy Free Gardening website. There are a number of articles on low-allergy gardening listed.

Date 2019-01-26
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Plant Answer Line Question

Keywords: Genista, Spartium junceum, Cytisus, Noxious weeds--Washington, Allergies

My question is about Cytisus. People with allergies complain about the Scotch broom that grows wild. Are the other tame varieties like C. x praecox going to be a pollen allergy problem also? I want to plant it as an informal hedge and my customers are worried. I want to tell them there is no comparison in the plants. Am I right?


To answer your second question first, Scotch broom (Cytisus scoparius) is an invasive European species that has given all brooms a bad name. Spanish broom (Spartium junceum) is also invasive, and is considered a Class A noxious weed in Washington State. There are garden-worthy brooms such as C. x praecox. A staff member here grew one in her previous garden for many years (and loved it). Some species of Genista, such as Genista stenopetala, are reportedly not invasive.

According to the book Allergy-Free Gardening by Thomas Leo Ogren (Ten Speed Press, 2000), Cytisus ranks 5 on the allergy index scale of 1 to 10, but allergy to this plant is uncommon, except in areas where there is a lot of it growing. Spartium junceum rates a 7, while Genista rates a 4, about the same as a begonia or a primrose.

Date 2018-09-26
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Plant Answer Line Question

Keywords: Rubus discolor, Allergies

This summer, I have been picking Himalayan blackberries in a local schoolyard. Twice in the last month, I developed sharp pains in my hand immediately afterward. There must be some type of neurotoxin in the bushes because the pain cannot be attributed to any cuts or scratches and is much more intense than a standard rash. What part of the plant could cause that reaction?


I checked Botanical Dermatology (Mitchell & Rook, 1979), Plants That Poison (Schmutz, 1979), the Plants for A Future database, and Toxic Plants of North America (Burrows/Tyrl, 2001) and found no references to any toxicity. Medical Botany: Plants Affecting Human Health (Lewis, 2003) describes the use of a blackberry-leaf tea for settling the stomach, so the leaves, when steeped, are not toxic. You do not say whether the pain is superficial, such as a skin rash, or deeper, which would make me wonder about some kind of stress or overuse syndrome.

Since we cannot give medical advice, you should discuss the incident with your health practitioner to see if you have some sensitivity to Himalayan blackberry, or to something else you encountered in that area. I found this link (to a page called Native Plants of Montara Mountain) showing the similarity in appearance between Himalayan blackberry and poison oak. It might be that you encountered poison oak without knowing it.

It may be that some other environmental factor (perhaps an application of herbicide) caused your distress. You should check with the school's grounds supervisor to be certain.

Date 2018-12-19
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Plant Answer Line Question

Keywords: Quirky, Ulmus, Allergies

Can the sap from an elm tree be poisonous to humans? The power company recently cut down an old elm in my garden and I brushed my hand against the stump and got a splinter. Within about twenty minutes my hand was swollen at least twice its normal size, was very painful, quite hot to the touch and itching like crazy. I ended up in the emergency room, and had to take antibiotics, but the doctor never indicated whether the extreme reaction had anything specifically to do with the type of tree.


We have an older book on plant-induced dermatitis, Botanical Dermatology by Mitchell and Rook (Greengrass, 1979) which includes elm among the trees which can cause "woodcutter's eczema." However, it may not be the sap of the tree itself which is the problem, but perhaps the lichens and liverworts which may be growing on the tree (some of which contain usnic acid and other substances which irritate human skin). Here is an abstract of an article which describes this:
Frullania liverwort phytodermatitis

If one were to saw elm wood which was covered in lichen or liverwort, the dust could be an irritant. You may have gotten a splinter which had dust on it. I'm not a medical professional, so I couldn't say with any authority what may have happened. However, a splinter of any kind can cause inflammation, and if you happen to be especially sensitive to a particular substance, whether it is the wood or sap of the elm, or traces of dust from lichens and liverworts that were on the tree's bark when it was sawed, then there might be a connection with the severe reaction you had.

Here is a link to an article about splinters from American Family Physician (June 15, 2003). It does mention wood splinters as a source of severe inflammatory reactions, due to the oils and resins they contain.

A chart which originally appeared in June 1990 issue of the journal American Woodturner lists different types of wood and their toxicity. Elm is included because its dust can be an eye and skin irritant.

Date 2019-01-05
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