Ivy Growing up a Maple Tree

I must comment on an article I recently read in a free gardening newsletter found in a diner. I hope this is not where most gardeners find their information. In the newsletter there was a question and answer column with highly suspect advice. The questioner wrote in asking if English Ivy

    Hedera helix

was hurting his maple tree as it was climbing up the trunk. I think the question was, maybe, wondering if the vine was some kind of parasite.

I have observed ivy climbing many houses, trees, fences, etc. and I can fairly well state that unless the tree is really weak and would fall down from the weight of the vine, it is really fine. The vine is just using the tree, or whatever, as support and is in no way a parasite*. It also cannot possibly overwhelm a big tree like a maple or oak.

Let me quote the fine answer this columnist gave:

“The plant is an aggressive climbing vine.”…”As the ivy climbs in search of increased light, it consumes and kills branches by blocking light from the tree’s leaves.”

I have never seen this occur. I have, however, seen ivy with no damage to the branches/trees for over fifty years of growing up the trunks. The columnist does not mention one slight problem with vines growing up a tree trunk and that is gypsy moth.

In the “old days” when gypsy moth was in its glory days and just moving into the midwest, it munched on many species of trees in residential areas. After feeding, the females seek a secret area to lay eggs. Since the pregnant females can hardly walk, they are so full of eggs, they like to walk down the trunks of trees and lay eggs under the cover of vines which are growing up the trunk. I would often find eggmasses hidden amoungst English ivy leaves.

This is

    not now

a real problem since gypsy moth has settled into a more moderate pest status with predators, parasites and diseases keeping it in check.

Back to this fine article:

“On the ground, English Ivy forms dense monocultures that exclude native plants, not just weeds. It also serves as a host for bacterial leaf scorch, a pathogen harmful to elms, oaks, maples, and other native plants.”

It does neither. I suppose this author has never supervised a landscape crew pulling weeds and “native” plants out of a bed of ivy. As for the unnamed bacterial leaf scorch, I know of no pathogen that attacks that wide of an array of plants and certainly not that array and ivy doesn’t get anything. Bizarre.

This goes on:

“Maple roots…With a mat of ivy on top are short-changed of water, and nutrients.”

Well, except for the fact that a maple tree has roots going all over in a very wide pattern and the ivy is usually in a small planting bed around the tree. I guess if the ivy was planted in a really huge bed, it would steal food from the tree about 5% but it doesn’t have the ability to block water that much. As for nutrients, that tree will get food just fine. The ivy is not that heavy a feeder.

I am weary of this odd question and answer. One of the things I have always disliked about gardening is there is a lot of wacky advice out there. I will put this article in my category of “wives’ tales.” Here is my advice to my loyal readers, do not get your gardening information from your local diner.

*Regarding parasitic vines, the reader may want to view a previous post on the true parasitic plant, Dodder.



One interesting plant found in Florida is the Golden Dodder, Cuscuta pentagona.  It is a parasitic plant that twines right handedly around the stem of its victim.  It rarely photosynthesizes for food, in fact some species cannot even make chlorophyll.  It sends root-like fingers called haustoria into the host and lives off the juices.  It can become so severe, the host does very poorly and dies.  Ususally parasites do not kill their host because it will put them out of business too.  Dodder is a seasonal plant that dies off in very cold weather, so they usually do not have time to kill their host in a season.  The severe cases I have seen in Florida must be multiple year infestations and the mild winters are not killing the dodder off as much. 

Dodder look like yellow spaghetti except for the flowers.  They are a flowering plant, and as such they produce seeds.  The seeds are long-lived in the soil and will germinate for years after an infestation has been cleared.  The seeds are an important weed seed that seed producers are always on the look out for.  It is a bad plant to come along with, for example, grass seed.  The customers would not want to get dodder from a contaminated batch of seed. 

I have only seen dodder in Michigan on rare occasions.  The type in our northern midwest has always been in Alfalfa.  I believe these pictures are of a different species, however none of it was flowering, so not sure. 

 The only cure for it is to remove or prune out the dodder from the host plant.  The haustoria can give rise to new infestations in the host if just a little bit is left.

In a bizzarre twist, so to speak, in Wiki, there is a bit about dodder being able to smell.  They say that some research has shown it grows toward pheromones emitted from possible host plants.  None of the dodder that I saw was sniffing around but here are some photos of a big mess.