Tuesday, September 8, 2009

Ivy League Ignorance

This is the Boston Ivy, Parthenocissus tricuspidata, that climbs up the cementitious shingles of my building. I didn't plant it; it somehow survived years of herbicides used to kill weeds that grew in this spot before I moved in. It grows up this brightly sunlit wall with no help from me.

This is some of that Boston Ivy. The landlord's men pulled it down and left it atop my perennials, still attached to its roots -so really not extinguishing it. I decided, then to cut it out, pulling up what roots I could. It'll come back again next year, it always does.

I like Boston Ivy. It cools the building by shading it, it's more attractive than my building, and it generally does no harm. Yes, I have to control it. I clip it where it grows underneath my perennials, but that's about it. If I owned the building, I would keep my eyes out for stems where I did not want them. 

Now that it's been pulled, the ugly painted brick foundation is not decorated with green leaves.

Landlords and owners of buildings worry that vines will work roots into the building, promoting wood rot or cracking the masonry. But Boston Ivy doesn't root from the vine.

Boston Ivy has little "suction cups" or disks that attach to the surfaces. They do not "root" the way an English Ivy roots into structures -all the roots of Boston Ivy are underground. It is possible that these roots could work their way into your masonry foundation, although they are likely to run along the wall as opposed to working their way through sound masonry. Of course, the question is -do you have a sound foundation?

Others worry that the vines are highways for insects. In fact, that is true for, say, ants. But those ants don't need a vine highway to get to your kitchen sugar or fat. They'll make their way through all the other holes and highways into your apartment. I cannot say I have ever had insects making their way in via vines. I have had ants in my place, but on the north, ivy-less side of the house (the bedroom! Old Halloween costume. Another time).

You might read on the web that the ivies produce an acid at its attachment points, etching the masonry, which slowly deteriorates your building. I cannot verify this claim, although decaying plants can produce humic acid and that could have some, albeit little, impact on your mortar.

The fact is that atmospheric gases, such as carbon dioxide, sulfur dioxide, and nitrogen dioxide, probably weaken masonry structures more than the humic acids derived from plant decay. Carbonic acid, nitric acid, and sulfuric acid are common components of rain water in industrial areas. As these acids accumulate in the wet areas of masonry, they react with the carbonates in the mortar, creating salts which accumulate and crystallize as the water evaporates. The crystallization of these salts creates what is known as spalling -the flaking off of pieces of masonry or stone. Brownstones are made with a type of sandstone and are especially susceptible to spalling.

It seems to me that people who complain that Boston Ivy's grip is so strong that it will pull masonry off buildings are confusing correlation with causation. The day a building owner goes to yank the Boston Ivy off the wall is the day he realizes that his wall is deteriorated, then blames the ivy, not our industrial society.

If you're the type to worry about masonry maintenance, it's just best that you do not plant any ivies on or near your buildings. If you have a wood-sided home, you may want to keep it clear of ivy for the sake of painting and other wood maintenance issues. But, do not plant any large shrubs or trees next to your home either -and we're talking closer than 20 feet. Boston Ivy is an easy target, but a poorly placed tree will send roots into your masonry foundation and shade your woodwork as well as any vine.

If you are a romantic, a plant lover, a greenery-softened home enthusiast, I bet you just may plant Boston Ivy or leave it well alone if it's already growing.


  1. I never knew that ivy was such a pest. I always wanted some growing on the side of my house but after seeing what a pain it can be then I shall avoid it at all costs.

  2. Unfortunately, being a nut for natives, I don't love Boston ivy, because it isn't a native. I wonder if Virginia creeper would be a suitable substitute? Both attach with suckers; both turn lovely colors in the Fall. I have seen one brick building with a thick coating of Virginia creeper on it, and it was beautiful.

  3. I and the stately homes of England thank you for digging into the mortar on that one.

  4. Michelle,

    Virginia Creeper is a relative, turns red, just has five-fingered leaves instead of three. I think it may be less aggressive up walls, but still can do the same work. Make it V. Creeper then!


    Of late been deep into chemistry anyhow. I poured Sulfuric acid into my drain to clear a clog. Plus, have made many a concrete thing, have seen the salt damage -people do not understand the nature of salts. They don't get mineral salts, dissolved salts, crystal salts, how salts are made- and lets not get into cation in the soil. OY! I hated chemistry in high school!

  5. I have a question. Hopefully you see this. My Daughter and her Friend just pulled down my 3rd year old Boston Ivy. It's still rooted but they pulled it all off my wall. Is there anyway to reattach or is it a lost cause???


If I do not respond to your comment right away, it is only because I am busy pulling out buckthorn, creeping charlie, and garlic mustard...