The mystery of Autumn Blaze maple unraveled
In this week's installment of "Growing Together," Don weighs in after a flurry of questions about the Autumn Blaze maple.
FARGO — I’ve received more questions about one plant than any other in recent memory. Those questions even outnumber inquiries about tomato blight and rhubarb.
The subject of all the discussion is the Autumn Blaze maple. Success with this tree type is truly a roll of the dice in large areas of North Dakota and a portion of Minnesota. Curiously, an Autumn Blaze maple can be spectacularly healthy in one yard, while a block away the same cultivar struggles continually with sickly yellow leaves, unnatural bark cracks and numerous dead or dying branches.
Why does success with Autumn Blaze seem to be a feast-or-famine situation? It’s easy to see why Autumn Blaze maple has caught the attention of anyone wanting a tree. The cultivar is fast growing, nicely shaped and the fall color is among the most intense of any shade tree with its glowing, long-lasting, deep scarlet color tones.
Autumn Blaze belongs to a group called Freeman maples, named after Oliver Freeman, who first created a hybrid group in 1933 by crossing two species: silver maple and red maple. Autumn Blaze is the most common of the hybrids, discovered in the 1960s and introduced into the nursery trade in 1982 by Poplar Farms Inc. of Waterman, Ill.
Like its silver maple parent, which is native in North Dakota and Minnesota, Autumn Blaze grows quickly, eventually becoming a large shade tree 40 to 50 feet high and wide, where adapted. Its shape is oval to rounded with a well-defined central leader. Its stronger branch angles make it less susceptible to storm damage than its weaker silver maple parent is, yet the wood genes it inherited from the silver maple make it a weaker tree than harder-wooded trees like sugar maple.
Autumn Blaze consistently develops brilliant orange-red fall color. The intense, vivid color, plus its rapid growth rate, give ample reasons to choose Autumn Blaze for a yard or boulevard tree.
So what’s the problem? Dr. Todd West, professor with North Dakota State University’s Woody Plant Improvement program, says about Autumn Blaze, “It can be an amazing tree or a complete failure. The reason it is such a hit-or-miss tree is because the tree doesn’t match our climate. Waterman, Ill., where it was developed, is classified as USDA Hardiness zone 5b, which explains the variable hardiness in North Dakota’s hardiness zones 3 and 4. The soil pH in Waterman is neutral and doesn’t match our alkaline soil.”
NDSU Extension Forester Dr. Joe Zeleznik further adds, “Autumn Blaze maple in this region is hit-or-miss, with more misses than hits. The iron chlorosis issue causes the worst problems. Where Autumn Blaze ‘hits,’ it’s fantastic with its beautiful color and very fast growth. Outside the Red River Valley to the east into Minnesota, where the soils are more forest-type with lower pH (slightly acidic), the tree does just fine.”
Slight differences in soil quality from yard to yard can explain why Autumn Blaze is hit-or-miss within close locations. Soil compaction during home construction, plus the mixing of topsoil and subsoil that often accompanies construction, result in variable soil. Favorable microclimates within neighborhoods can help Autumn Blaze escape winter injury.
Is there anything that can be done to increase the odds of success?
- Amending the existing soil to match Autumn Blaze’s requirements is nearly impossible. Tree roots quickly spread horizontally in the soil, reaching a considerable distance from the tree itself. Attempting to change the quality or pH of a massive soil amount is like trying to change the color of the ocean by adding a little food coloring.
- Follow these important steps when planting: Remove the tree from its pot and gently pull all circling roots outward from the edges and base of the soil ball. Dig into the rootball to find the top flare root branching from the trunk, and situate the tree at a depth so that root is barely covered with soil, which might require scraping away soil from the surface of the root ball. Planting holes need to be wide, but not deep. Circling roots and too-deep planting are common causes of tree failure.
- Observe young Autumn Blaze carefully for signs of iron deficiency chlorosis, in which leaves become yellow, while the veins remain green. Treat immediately with chelated iron, available at garden centers, following label for directions and frequency of application.
- Mulch around trees with shredded bark to eliminate mower and trimmer injury.
Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at firstname.lastname@example.org or call 701-241-5707.