Have I ever guessed right on some unknown tree? Oh well, here's another. I can find only two hits from google on Quercus palustris Variegata (it didn't really show how to write that as it was all in upper case), which the grower described as "The unbelievable rare 'Variegated Pin Oak' ". Is that what these are? These are two private condo plantings east of Burrard St near False Creek. They're not mentioned in Straley's Trees of Vancouver (1992) - maybe not even planted yet? Two of the four trees at this location are variegated. There is a little mottling on the other two trees, so I wondered if they'd reverted. At this other building two blocks away, there are five trees, two of which are clearly variegated; the other three have a few areas with some mottling.
I did wonder about that, and whether the green ones were what was planted, but I convinced myself that not all variegation is evidence of distress, and the pattern is so regular and attractive that I talked myself out of the disease angle.
Highly doubtful that the one (or two) was planted as a named cultivar. There was a 'Mills Variegated' patented in 1969 but it was "Not known to be in commerce" (Jacobson, North American Landscape Trees, 1996, Ten Speed, Berkeley). http://patimg2.uspto.gov/.piw?docid...1=PP02899.PN.%26OS=PN/PP02899%26RS=PN/PP02899 Even if the one looks like a described named form it is probably an independent occurrence. White-mottled seedling variants are frequent among some much-grown trees such as Amur maple, English oak, golden rain tree and Japanese pagoda tree. Often this leaf color variation quickly disappears, sometimes not. I have a seed-raised Pagoda tree on Camano Island that is now above head height and still producing partly whitish leaves.
Well, three days ago I had never heard of pin oaks, and now I'm seeing them every place I go, and it seems almost all of them have this kind of colouration to some degree. Now I wonder if that's just what the new leaves do. Or maybe this is just a white mottled leaf year? None of the other trees has been as striking as the one in the first posting. The first photo is at the Aquatic Centre, pin oak leaves in front of a red oak. The other two photos are on a road at False Creek. I think in the next photo, the tree on the left was also pin oak, but pretty much green; the leaves in the last photo are from the tree that appears to the right of that one in the second photo.
So you mean the leaves could be examined to see if the yellowing were due to virus infection or soil deficiency, or was hereditary indicating true variegation? I have no idea how to go about having that done. Do I just show up at UBCBG with some leaves?
In the Vancouver area, when we have a long period of cool weather in spring, many trees from warm-spring regions exhibit this kind of chlorosis. This has been one of the coolest, wettest springs on record. I suspect that cold soil is the problem and that the mobility of soil magnesium or iron, or nitrate availability may be the cause of the yellowing. On my way to work, I pass by a group of large red oak (Quercus rubra) trees. The leaves on these trees all looked a bit yellow when they emerged this spring. One of the trees is still showing distinct chlorosis in the upper branches, which makes it appear that the top of the tree is in sun, and the adjacent foliage is in shade.
Frequent on Syringa reticulata in this area, another hot climate species. This year whitish mottling of new growth of various kinds of trees and shrubs can be seen. A presumably related phenomenon I have noticed in recent years is marked greening up as summer approaches, presumably due to warming of the soil and increased nitrogen availability.
Here is a pin oak I saw at UBCBG today, in the Carolinian forest. If the first tree I posted had looked as irregular as this, I think I'd have recognized it for chlorosis. I'm not saying I don't buy your story. I'm just saying my cholorsis is prettier than your chlorosis. Pretty enough that it had me fooled.
The result of phosphate overfertilizing is leaf chlorosis. Phosphorus is known to compete with iron and manganese uptake by roots, and deficiencies of these two metal micronutrients causes interveinal yellowing. It's my belief that many of the chlorotic shrubs we see in urban landscapes are suffering indirect iron (or manganese) deficiency from overapplication of phosphorus http://www.puyallup.wsu.edu/~linda chalker-scott/Horticultural Myths_files/Myths/Phosphate.pdf
I have a great deal of respect for Linda Chalker-Scott, and I often agree with her well-researched, sensible diagnoses; in this case, however, I don't think phosphorus is the culprit (or the main culprit, anyway). As I've been seeing this sort of chlorosis quite a bit in areas where I doubt there have been any phosphorus additions, I'm of the opinion that saturated, poorly oxygenated soils are likely to blame. Such soils, especially those excessively amended with inherently iron-deficient organic matter, are tough on many plants. I certainly wouldn't rule out phosphorus, but in the case of the Carolinian Forest Garden pin oak shown above, I'm pretty sure it's excessive incorporation of wood chips (and low oxygen) that is the affecting the plant.
I don't know that she thinks this early season variegation has anything to do with phosphorus, what I put here is the extent of her remarks on the subject (phosphorus-induced chlorosis) that I have seen.
Fair enough. I've certainly seen chlorosis in the landscape that could have been caused by excess phosphorus, particularly in higher pH soils. I recall that the rose garden at a local garden had to have some of its soil replaced as the years of accumulated bonemeal (a handful at the bottom of the planting hole for every rose) had created a phosphate toxicity.
I was very interested to find no scientific evidence that suggests roses need high levels of phosphate for any reason. As I’ve mentioned in this column previously, perennial landscape plants in urban areas are rarely deficient in any nutrient other than nitrogen. In our landscape restoration projects at the University of Washington, soil tests have routinely shown that phosphate levels are at least adequate and sometimes more than adequate for normal plant growth. Addition of any non-deficient nutrient to a landscape is a waste of time and money, and can injure soil organisms. This is particularly true of the mycorrhizal associations that occur between various fungi and plant roots http://www.puyallup.wsu.edu/~Linda ...ral Myths_files/Myths/Roses and phosphate.pdf
