Acer saccharum 'skutchii' - Mexican Mountain Sugar Maple
This is a somewhat extended version of some notes on a plant we‟ve been impressed with for some time. The cloud forest sugar maple, Acer saccharum ssp. skutchii, occurs as five disjunct populations, with four in Mexico and one in Guatemala. First described in Guatemala in 1936, this species is the southernmost sugar maple, a rare relic from the Miocene era, probably separated from those in North America in the Pleistocene. While there‟s very little information available, an internet search reveals an excellent thesis on Acer skutchii by Yalma Luisa Vargas-Rodriguez who graduated from Louisiana State University in 1995. For those readers interested in the ecology and natural range of the species, this is the ultimate source of research information.
The tree is similar in many respects to Acer saccharum, sugar maple, and Acer saccharum var. floridanum (syn. A. barbatum), the Florida maple, but features larger leaves, and perhaps the biggest samaras found in Aceraceae. Our oldest tree is located on the north side of the headhouse in the SFA Mast Arboretum and was planted in 1994, an acquisition made by Carl Schoenfeld and John Fairey of Yuccadoo Nursery who collected seed from trees in Tamilupas, Mexico. In spite of intense competition with a Chinese juniper, long since gone, our Skuch maple thrived without irrigation or much attention during the first few establishment years. This tree has been through extended droughts. Now over forty feet tall with a 49” circumference about four feet above the ground, this tree sports excellent fall foliage color, varying from butterscotch yellow in some years to reds, oranges and yellows in others. New growth can be quite striking on some clones, varying from ruddy bronzes to pinks and salmons. The bottom image on this page is via Brian Upchurch, a young tree featuring salmon colored new growth. A queen of marcescents, this tree can hold leaves a very long time into the winter. The two images at the top of the document are early winter shots - 2009 and 2010. Over the years, we‟ve shared this species with our gardening friends in Austin, San Antonio and Fredericksburg and they report it‟s quite alkaline and drought tolerant, certainly a plus for maplephiles in those regions. However, Dr. Mike Arnold, Texas A and M University, reports that Acer skutchii has failed to deal with the high salinity irrigation water in College Station (250 PPM Na and 500 PPM Bicarbonates). Whether irrigated by sprinkler or microsprinklers, growth was poor. Leaves were cupped and took on a bluish cast, and the trees failed to survive in their container trials. I have personally seen the same thing here in Nacogdoches County and find the species leaf intolerant to irrigation water that is burdened with either Ca, Mg, or Na. Quite tolerant if dripped or micro sprinkled and foliage is unaffected by the irrigation system.
We have germinated seed and have had some success rooting cuttings. In the Fall of 2009, after the samaras had fallen from our sole tree, we applied about an inch of composted pine bark fines over the entire root zone. Lo and behold, several thousand seedlings emerged which were carefully dug and shipped to a wide variety of gardens, nurseries and researchers in the USA. Typically, ten percent or less of our tree‟s seed are viable, most are empty. As far as we know, SFA may be the sole seed source in the world!
To improve on seed availability, viability and to seek out superior clones, SFA Gardens planted 277 young one gallon seedlings in a planting at SFA‟s Science Research Center which is about five miles from campus. This is a cooperative project with the College of Science and Mathematics and SFA‟s Physical Plant, an agreement to use this space for plant evaluation. Dr. Bea Clack is the lead contact on this project in that College. Trees were planted on a 15‟ X 15‟ spacing in Dec 2010. Weed control via backpack sprayer application with glyphosate. In February 2011, Lijing Zhou, Graduate research assistant in the Arthur Temple College of Forestry and Agriculture, applied fertilizer via one cup of 13-13-13, a complete fertilizer.
After a record dry fall and winter 2010 – and spring 2011, the decision was made to install a drip irrigation system. We used ¾ inch black poly pipe with ½ gph Netafim emitters which was nstalled in mid-April 2011. Bone dry subsoil. The irrigation system guarantees survival of this important plant material and once the trees are a year or two old, they should be able to deal with droughts and dry times. This project is yet to be successful. Will someone send some real rain (April 26, 2011 note to file). Success! Plan is to provide 4 to 6 gallons per week at the plant – the total applied in two applications per week.
Other maples: Of course, there are other maples suitable for central and western regions of Texas. Dr. Mike Arnold, Texas A & M University, reports that in their work at College Station, an Ed McWilliams selection of Acer rubrum var. drummondii, the Drummond red maple, has been particularly tolerant of the high pH soils of College Station - and tolerant to very poor quality water. A. buergerianum, Trident maple, has shown some promise in western sites and there may be clones still untested that might surprise our industry. Mike also reports that the Amur maple, A. tataricum ssp. ginnala (syn. A. ginnala), has been a surprise in their inhospitable garden site. The Amur maple has performed well here in Nacogdoches for over twenty years with bright red to burgundy fall color. I have personally observed A. truncatum, Purpleblow or Shantung maple, doing better under higher soil pH conditions than I expected, and Greenleaf Nursery will soon be marketing a Keith Johanssen clone named „Fire Dragon‟ (Metro Maples) that features red fall foliage. Many years ago, Benny Simpson and Billy Hipps reported (American Nurseryman 177(5):26-35) that certain provenances of A. grandidentatum, Bigtooth maple, and the Caddo maple, a unique genotype of A. saccharum from southwestern Oklahoma, were particularly good performers in higher pH soils. There are two superior varieties of Caddo maple, „John Pair‟ and “Autumn Splendor‟. Still, when the dust settles on maples for western climes, the list is not a long one. Skutch maple may be just another possibility.
January 2012 status – Out of 277 plants set, we lost about twenty, which were replaced in December 2011 from our inventory of container plants at the SFA Mast Arboretum. Half of the plants lost were due to deer damage and the other half succumbed to something else. With 35 inches in 2010 and the same in 2011, this site has been extremely dry and hot this first summer. The drip system operated flawlessly. The image of the planting above was taken in December 2011 and dramatically shows several pines in the background that are now victims of this terrible drought. Now that the trees have survived the first critical establishment year, we‟re expecting some great growth in 2012!
Dave Creech, Director SFA Gardens