In the garden: Quercus fusiformis 'Quartz Mountain' and the winter of 2019-2020.

Quercus fusiformis, commonly known as the Plateau Live Oak or Escarpment Live Oak, is a close relative of the better-known Quercus virginiana, or Southern Live Oak, the iconic evergreen (hence "live") oak trees of the Deep South. In fact, for a number of years and in some references still, Quercus fusiformis is listed as Quercus virginia fusiformis. Currently the splitters have prevailed over the lumpers, so the Escarpment Live Oak is its own species. But regardless, this relative from Northern Mexico, Central Texas, and Oklahoma has a few advantages over its eastern kin, at least for Colorado gardeners. First, it reportedly has greater cold tolerance than typical Q. virginiana, pretty much a complete growing zone (USDA zone 6a for Q. fusiformis, USDA zone 7a for Q. virginiana). Second, Q. fusiformis, coming from much drier regions than Southern Live Oak, is very drought-tolerant. With a definite preference for calcareous soils, this live oak is suited for Colorado in every way but for one thing: hardiness. But it's awfully close. So, I decided to trial this oak. I sought out a seedling from one of Quercus fusiformis' northernmost populations, the Quartz Mountain region in southwestern Oklahoma, right on the border of USDA zone 7 and zone 6. I received and potted it up in late winter/early spring of 2019, then planted it out in the landscape once my area was past the likelihood of freezing, sometime in late May. It grew an additional few inches last summer, handling dry daytime heat (up to 100F), cool nighttime drops (down to 50F), ice-cube hail, periods of drought -- in general, typical Colorado weather. But my question was, "How is this seedling oak going to handle our winters?" Would it drop its leaves? Would it even survive? To hedge my bets, I covered it with some protection during a couple of our coldest months, but not very often. After all, seedlings just getting established are typically much more sensitive than mature, established plants of the same species. And while we did not see temperatures as low as we did a few years ago (-19F!), we did record -7F once and -5F a couple times. And even though we only hit -7F once, we spent many more hours than average below (usually well-below) 32F. Then, once the weather started to warm late March into April, we were hit with an Arctic blast that dropped the overnight temperature to 13F following almost two weeks of 65F-75F sunny days. The damage? A picture's worth a thousand words, so here's the pic:

Quercus fusiformis 'Quartz Mountain', Milliken, CO. Photo by William Jury.

As you can see, Quercus fusiformis 'Quartz Mountain' is still very green. It did suffer some burn along the edges of some of its leaves, and it did drop a few older leaves, keeping all of the newer leaves it grew last year. It was planted in a south-facing location, meaning the soil had a chance to warm on the few days we actually saw above freezing. Will it survive -19F? It probably depends on what the weather is doing in the days preceding and following those temperatures. But I am hopeful. This is a really cool oak, one of the hardiest evergreen oaks, and I look forward to seeing how it performs in the years to come!