Comments on: Frederick Dobbs On The Sub-Zero Garden

By: Frederick Dobbs

Frederick Dobbs — Tue, 23 Feb 2010 01:17:24 +0000

Dear Sabra, Thanks for your comment. I would agree that yarrow is pretty easy to grow generally, and it’s endemic pretty much everywhere in North America. I think allelopathy is probably not what’s going on. Had you not mentioned pH, I would have. Oak will of course happily grow a pH much lower than yarrow. Yarrow likes a sunny spot with good drainage and light soil. Could the problem be something as simple as this?

By: Sabra Ewing

Sabra Ewing — Tue, 23 Feb 2010 00:58:05 +0000

Hello,
I would like to share that we have wondered if a red oak adjacent to a 30 x 30 mixed perennial island bed, is the culprit responsible for the partial stunting to perishing of all types of Yarrow. Of course this is the clients favorite flower! Yarrow does just fine in our other gardens in a 30 mile radius that have the same ph levels. Also, of all plants yarrow does just fine in the wild here in Vermont most nursery men and women respond ‘Yarrow?” but that’s easy to grow!”

By: Frederick Dobbs

Frederick Dobbs — Mon, 15 Feb 2010 19:35:41 +0000

Thanks for your kind words, pk.

By: pk

pk — Mon, 15 Feb 2010 19:17:42 +0000

I am amazed at your intelligence. Gotta love what you do…thanks for the lesson.

By: Frederick Dobbs

Frederick Dobbs — Sat, 13 Feb 2010 21:33:09 +0000

Great question, Claudine. I don’t know that anyone has stated how long a plant must have been growing in a region to be considered “native”. Is Kentucky blue grass native? It came to the USA with the colonists nearly 400 years ago. I’ve heard the argument made that a species is not really native if the germplasm didn’t actually come from the area where it is being cultivated; I’m talking about counties here. So, it may depend on whom you’re talking to.

No doubt, as mountains rise and the climate changes (over eons), our current native plants have supplanted our former native plants. Quite rapid evolution (10,000 years say) is seen in Arctostaphylos spp. (manzanita). See http://www.cnps.org/cnps/publications/fremontia/Fremontia_Vol35-No4.pdf.

I think you’re also quite right about native plants; they’re probably invasive as much as they’re opportunistic and maybe aggressive colonizer. Not all exotics are invasive. It’s only a small subset that show greater abundance, density, or competitive dominance in their introduced ranges—garlic mustard, purple loosestrife, and knapweed come to mind. But there are plenty of native plants that are opportunistic and aggressive colonizers. Common ragweed is an example and I believe it’s native to all 48 lower states—no one of course would think of using it horticulturally, but you get my meaning.

By: Claudine

Claudine — Sat, 13 Feb 2010 20:39:50 +0000

A very interesting article.
I have a question that seems unrelated, but as the natives go. During my studies as a landscape designer, emphasis was on natives, which I use as often as possible. For me, though, some are invasive. Do we know for how long those plants have been growing on the US territory and could it be that they prevailed over more ancient plants?
Seeds come from boats, logs, birds, wind, etc

By: Frederick Dobbs

Frederick Dobbs — Sat, 13 Feb 2010 18:31:26 +0000

Dear Dennis, Good observation. I believe that the toxic compound(s) produced by tree of heaven do persist in the soil, so you may well be right. I found one reference that might be useful, if you feel like persuing it—Lawrence et al. (1991). The ecological impact of allelopathy in Ailanthus altissima (Simaroubaceae). Am. J. Bot. 78:948–958. It may be available on the internet, but if not and you’re in Madison, you can certainly get it at Steenbock Library.

Lake Park is lovely this time of year.

By: Dennis

Dennis — Sat, 13 Feb 2010 18:05:10 +0000

I am suspicious of an alletropic effect from Tree of Heaven (Ailanthus altissima).
In Lake Park (designed by Fredrick Law Olmsted)here in Milwaukee, a matched pair of Redbuds were planted on either side of the grand staircase about 10 years ago. The one on the south side of the staircase is half the size of the one on the north side. A tree of heaven had been removed prior to planting on the south side and may have contaminated the soil. All other growing conditions are identical.

By: Pat

Pat — Sat, 13 Feb 2010 17:27:00 +0000

A very good article. Just shows we don’t know everything yet and there is much work to do.

By: Frederick Dobbs

Frederick Dobbs — Sat, 13 Feb 2010 01:29:17 +0000

Dear Cara, There are commercial inoculants, but I don’t know how well (or if at all) they work. Overly cultivating your garden can disrupt mycorrhizal fungi, and some plants (cabbage-type plants) can suppress mycorrhizal fungi. Probably the simplest way to encourage mycorrhizal fungi in your garden is through mulches and composts. Mulches and composts improve soil and plant health and control weeds. They improve drainage, lower soil temperature in the summer, and insulate roots from cold in winter. They inhibit undesirable microorganisms such as soilborne pathogens and stimulate beneficial microorganisms, including mycorrhizal fungi.