I have your wonderful book "Poison Plants in the Pasture" in which you talk about the Acer rubrum or Red Maple. I am preparing land for pasture on Vancouver Island, BC and have 6 big beautiful Acer macrophyllum (Bigleaf Maple or Oregon Maple) trees in the pasture. I had them identified by a Herbologist who feels they do not have the same toxic properties as the Acer rubrum. Do the Acer macrophyllum (Bigleaf Maples) have the same toxic properties or are they safe to have in my pastures? They would provide wonderful shade in the summer if they are safe. I have a faller booked to take them down tomorrow. Should I cancel?
I'm replying just in case Dr Deb does not get a chance to answer before your arboristarrives. It would be a shame if your trees were removed needlessly, especially if they are well established.
I work in botany, and while I am not familiar with many North American species (we are concerned mostly with Australian natives and weeds), I am accustomed to searching for plant information on the web.
A quick search does not yield any information suggesting Acer macrophyllum is toxic to horses or any other organism. In fact there are plenty of references that A. macrophyllum sap, bark, shoots and leaves can be eaten by people and livestock which suggests that it doesn’t contain large quantities of toxic compounds. It is certainly not as toxic as A. rubrum (Red Maple), which is well documented as being extremely poisonous to horses.
Have you received information that A. macrophyllum could be toxic?
I’m interested to hear yours and others take on Maples as pasture trees, Dr Deb. Does anyone have maples in their pasture? Do you horses eat the leaves? Or the bark? I have a maple near my horse’s paddocks and, before it was fenced off in a paddock restructure, my horses loved to eat the autumn leaves as they fell. I presume they are high in sugar, which is not much of an issue for my TB types, but may be if you have horses prone to founder. I have forgotten which species it is (certainly not rubrum).
I’d wait to here back from Dr Deb, and perhaps obtain some more local information, before you decide to remove your trees.
Yes, Emma, what you've said is correct so far as I can determine too. The only species of Acer (Maple) that has reported toxic properties is Acer rubrum, the Red Maple.
Red Maple leaves are toxic when they blow down from the tree -- in other words, they are toxic when passing from the green to the brown, dried-up state. Thus it is the kind of blow-down you would get in a high wind, which might tear branches and twigs off the tree that had leaves on them that were still green. Then those green leaves lie on the ground and they are toxic as they then go through the process of becoming dried. No one yet knows what the toxic principle in Red Maple actually is, although it does appear to be the plant itself and not some fungus growing on or in the plant.
So -- the main issue here is to be absolutely sure that the trees in Vancouver are not Red Maple. If they are any other species of Maple, they will be OK and it will not be necessary to cut them down. -- Dr. Deb
My trees thank you as well. I will leave the big beautiful trees as I am certain that they are not Red Maples. I did multiple web searches as well and although I found numerous articles on the red maple I was unable to find anything concrete on the big-leaf species.