Last summer was a sit, wait and worry, summer. The previous winter of ‘16-‘17 was a hard one here. Because my Butia capitata had been sailing through its previous nine winters, in this location, without damage, I assumed it would be OK this time, but it wasn’t. Our 12” snowfall weighted the fronds down splaying it open and no doubt allowing moisture, ice etc. to penetrate down into the trunk to the meristem, the critical tissue from which all growth in the plant begins. Last summer not one new frond emerged, an indicator that the meristem was damaged or killed. The good thing was that there was no sign of rot. The new ‘spear’ could not be pulled free….The same winter killed my Trachycarpus martianus darkening and shattering much of the fronds’ cell walls and structure in a way typical of many freeze damaged plants. Its center spear, the newly emerging fronds, pulled free. My Butia spent last summer in a kind of limbo. This last winter was much more mild. Now, finally, with the heat settling in around us, those old spears are growing again, their leaflets opening wide, while their long rachis/stems, fully extend and arch! New spears are forming still pressed tightly against the most vertical and longest of these whose leaflets you can see below just beginning to fan open. This is slower growing than the Trachys, working on opening its third frond of the year! Typically my Trachycarpus fortuneii form 15-20 fronds in a year. I’m wondering now how this lost year of growth will effect the Butia’s trunk diameter. Because of how Palms as monocots grow, I suspect that it will result in a narrowing of its ‘waist’, with a swelling back to normal above when more normal winters prevail.
As monocots Palms do not have cambium tissue. They cannot add circumferential growth over time. They don’t form ‘rings’ in their ‘wood’, nor do they form ‘bark’. You cannot kill a Palm by girdling it, there is no cambial tissue to damage. Their trunks are comprised of a more or less uniform cortex material that contains scattered xylem and phloem vessels. Their growth initiates from the basal meristem, the cortex and vascular tissues, the fronds/leaves and their large inflorescences. Fronds/spears arise continuously extending and expanding to their mature form over time and then ‘migrate’ outward’ as newer/younger fronds continue to emerge. Each new frond pushes slightly higher than the previous while the trunk/cortex tissue rises and expands supporting the maturing fronds and inflorescences. The inflorescences emerge in the Spring all at once from older cortex tissue, outside and below the ever emerging spear.. Both of these continue moving outward as the trunk/cortex continues to rise and expand. In cases of severe drought growth is reduced and the expanding cortex does not attain its typical diameter. When conditions become more favorable the growth rate increases and the trunk/cortex is again able to expand to its normal diameter leaving a ‘narrow waist’ below the extending trunk in a way similar to the tighter rings in the wood of dicot woody trees when they are drought stressed. In my Butia there was no vertical growth, no emergence of spears or the accompaning inflorescences last summer…but there appears to have been some growth of the cortex.
My suspicion is that the cold damaged my meristem, but not severely, and cortex tissue with its dispersed xylem and phloem vessels continued to expand, at least at its periphery. This has resulted in what appears to be a ‘flattening’ of the leading tip of the trunk. Normally the new growth emerges in sharply tapering growth. In my Butia the outer region of the trunk seems to have ‘caught up’ somewhat with the emerging center. It is also my speculation that the meristem, has over time, been able to grow back, covering the damaged portion in a manner similar to the way woody dicots add growth and callous tissue surrounding and ‘including’ wounds. If any portion of the meristem died and began to rot, that damage was limited and contained. This would explain the return of healthy growth. It would also follow that a significant distortion in the trunk will become evident as growth continues over the coming years. While dicots ‘record’ their growth history through their rings and the resultant layer of ‘wood’ enveloping the entire woody structure over time, Palms express their stress physically in a more linear fashion by being shorter and narrower over those periods, broader and taller over periods of supportive conditions. We shall see! For now I’m just happy that my Butia seems to have returned to the land of the living.
If you’re curious as to what our winter of ’16-’17 was like, the introductory section of my previous post, “The Strength to Stand: Surviving the Load of Ice and Snow in Portland”, discusses it.
For a discussion of the growth and performance of my Butia capitata prior to this, see “Butia x Jubea: A Pinnate Palm for Portland – First Test…for me”
Another posting, “Palms I Have Grown”, profiles the Palms I’ve grown in my own garden up to that date.
And, finally, this posting, “Palms, Bananas, all Monocots…Oh My” takes a more detailed look at the growth and characteristics of the group of plants long identified as Monocots, including the Palms, and their differences within this group. This posting looks at Monocots as a group by examining their leaves, stems, flowers, roots and growth as a group. It doesn’t break out Palms, Bulbs, Grasses, Bamboos, Orchids, etc. separately which requires the reader to peruse each section to find the specific discussion of each sub-group…sorry, but I was attempting to establish the links, commonality, between all of these plants.