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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Saturday - May 05, 2012

From: Liberty, TX
Region: Southwest
Topic: Poisonous Plants, Herbs/Forbs
Title: Is wild foxglove poisonous to dogs from Liberty TX
Answered by: Barbara Medford

QUESTION:

Is penstemon cobaea (wild foxglove)poisonous to pets, specifically dogs. I was thinking about adding this to my native Texan wild flower section of my backyard.

ANSWER:

If you look at our webpage on Penstemon cobaea (Wild foxglove), you will note this sentence under Condition Comments:

"Wild foxglove is not related to the true European foxglove."

So, we went looking for information on the European foxglove. Turns out it is from a different genus, Digitalis, not even related to the genus Penstemon, which is our "foxglove." Here is the information from that article on Digitalis purpurea

 Digitalis purpurea (Foxglove) These familiar biennial plants are members of the Snapdragon Family native to southern Europe and Asia, but highly prized in North American gardens for their tall spikes of beautiful, bell-like flowers, in pink, blue, or mauve, with dark spots inside the lip.  Foxgloves are the pharmaceutical source of the heart drug digitalis, which is poisonous in overdose. The plants are also helpful in preserving other species of cut flowers with which they may be arranged in a vase, or in stimulating the growth & endurance of garden root vegetables, especially potatoes, with which they may be planted. Poison is located in the sap, flowers, seeds, and leaves of Foxgloves, but the greatest concentration of the toxin occurs in the leaves, even dried ones.  Poison type: Digitoxin, a glycoside which stimulates the heart.  A carefully prescribed dose often has miraculous effects on people with heart conditions, but an overdoes may be fatal. Poisoning can occur accidentally from consumption of  the leaves or flowers by livestock, or children who are attracted by the showy flowers, or the nectar, both of which contain the glycoside poison. The sugar in the glycoside breaks down during digestion, releasing the active chemical.  Adults are occasionally poisoned by the misuse of herbal preparations- tea from dried Foxglove leaves is traditionally a diuretic- or by overdoses of prescribed digitalis.  Another possible cause of  is misidentification.  The leaves of Foxgloves are easily mistaken for those of Comfrey, which are traditionally brewed for tea; both share the same general form and a coasely hairy surface. Additional confusion occurs because, in its first year, Foxgloves produce only leaves, no flowers.  Foxglove leaves, however, have finely toothed edges, whereas Comfrey leaves are smooth.  Digitoxin is dangerous, so Foxgloves must be treated with caution.  Symptoms of poisoning are increased heart rate, leading to heart failure in the case of overdose. Other symptoms include stomach upset, mental confusion, and convulsions"

Now, let's look at the Penstemon genus, and see if it has any poisonous threats. From a previous Mr. Smarty Plants answer, here is a list of databases that would be useful in searching for poisonous plants. It is usually better to search on the scientific name, so we will look at these databases for Penstemon cobaea.

 

None of these showed any species of Penstemon as poisonous. But, you need to be really sure what you are buying-these common names can be tricky.

 

From the Image Gallery


Prairie penstemon
Penstemon cobaea

Prairie penstemon
Penstemon cobaea

Prairie penstemon
Penstemon cobaea

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