Growing Japanese Maples in Wisconsin
Japanese Maples are a highly coveted landscape plant for many good reasons. They have a lot going for them, such as distinctive foliage in leaf form and color, interesting shape, overall size, and beautiful fall color. They are sure to inspire awe and are some of the easiest trees to identify.
What is a Japanese Maple?
The term “Japanese Maple” is somewhat of a misleading name; it has two meanings. One is applied in the nursery industry to a group of small ornamental trees. For the serious dendrologist, the second meaning indicates all the species of the genus Acer which are endemic to Japan and portions of neighboring regions. Many species labeled as Japanese Maple may also be native to China, Korea, eastern Mongolia, and even southeast Russia. In the United States, all cultivars of a few species of Acer are grouped into this general term of Japanese Maples. Included are all the cultivars and forms of Acer palmatum; however, we also find listed cultivars of A. japonicum, A. sieboldianum, A. psuedosieboldianum, and in some cases, A. buergerianum and A. crataegifolium.
A. palmatum (like the ‘Bloodgood’ variety shown above) and A. japonicum are at the center of this labeling. The cultivars and variations of these two species have been bred, selected, and propagated for over 400 years by the Japanese resulting in more than 250 cultivars between these two species alone.
During the last 200 years, these cultivars have found their way into horticultural collections, arboreta, and the nursery industry. Today, there are at least a thousand varieties of Japanese Maples. The genus all maples come from, Acer, is known to readily interbreed, crossing with one another easily, which further creates a considerable variation in their form, habit, bark, leaf shape, and color.
Throughout this article, we will use the term “Japanese Maple” when referring to the many different maple species commonly called Japanese Maples, not one species in particular. Japanese Maples thrive best in zones 5-9 but can be successfully grown in colder climates. Check out our article on USDA Hardiness Zones if you would like to understand better what hardiness zones are, how they work, and to see a map.
Despite much of Southeastern Wisconsin being listed as zone 5, our windy winters and late spring frosts make growing Japanese Maples tricky. Wisconsin’s winter winds are often closer to temperatures in zones 4 and sometimes even 3. For this reason, Japanese Maples are considered marginally hardy in Wisconsin. But don’t despair! They can and have thrived here, but only under ideal conditions. You can succeed in growing zone 5 hardy Japanese Maples, but special precautions must be taken to increase the chances of survival and longevity.
Ideal light conditions for a Japanese Maple would be dappled light or part shade. Japanese Maples can grow in full sun but will still need some shade throughout the day as those grown in full sun are prone to leaf scorch, especially in hot and dry locations. Some varieties are less tolerant than others of full sun, such as dissectum Japanese Maples, which are especially prone to leaf scorch. Dissectum Japanese Maples are easy to tell apart from others as the foliage looks like lace from a distance, but up close, you’ll see that the leaves have long, slender “fingers” that are deeply lobed. With foliage much finer than other Japanese Maples, intense sunlight can burn leaves quickly if allowed to dry out.
Japanese Maples need a couple of hours of unfiltered sun, but if the planting location is primarily shady, you will have a much happier plant.
Examples of dissectum Japanese Maples include:
- Crimson Queen (Acer palmatum var. dissectum ‘Crimson Queen’)
- Red Dragon (Acer palmatum var. dissectum ‘Red Dragon’)
- Waterfall (Acer palmatum var. dissectum ‘Waterfall’)
- Tamukeyama’ (Acer palmatum var. dissectum ‘Tamukeyama’)
Dissectum maples often have a weeping form but are not exclusively found as such.
How to Protect Your Japanese Maples in Winter
Wisconsin’s Winter Winds
Successfully growing Japanese Maples in Wisconsin begins with proper siting. You'll want to choose a planting location that will naturally give your tree permanent protection from the winter winds. The prevailing wind direction in Wisconsin is from the West. The best spots to plant a Japanese Maple are those on the eastern sides of things like buildings or evergreen hedges. This protects the tree from sweeping western winds and strong sun. In general, Japanese Maples are best grown on the South to Southeast side of your home.
You will also need to apply a generous layer of bark mulch over the tree's root zone and water it thoroughly throughout the fall before the ground freezes. Your tree will benefit from having more water stored up going into the winter season and will come out of dormancy refreshed and ready to grow.
It is important to keep in mind that you should refrain from using rock or stone mulch as it can harm the health of the Japanese Maple. Rock and stone mulch raises the temperature of the soil, can change the pH level to be more alkaline, and because it doesn’t break down, provides no benefit to the soil in the way that wood mulch does.
Other Common Winter Issues
In addition to cold temperatures, sunscald and frost cracks are also issues that can impact the health of Japanese Maples.
Sunscald happens during sunny, cold winter days on the south to the southwest side of the tree. When the bark on the tree warms up on sunny days, the dormant cells within the plant become active in response to the sun's warmth. The activated cells lose some of their cold hardiness and are injured when the temperatures drop during the nighttime. This damage can cause cells to die, leading to the discoloration of the bark. The repeated switch from warm to freezing temperatures causes the inner layers of bark to expand and shrink repeatedly; eventually, this tension causes a frost crack.
Frost cracks themselves likely won't kill a tree, but they are an open invitation for insects and disease. Younger trees have thin bark, making them more susceptible to this damage. As most trees mature, they develop thicker bark and become less prone to sunscald or frost crack injury.
Fortunately, protecting trees from this kind of damage is easy and inexpensive. Sunscald and frost cracking can be prevented by wrapping the tree trunk with a white or light-colored guard to reflect the sun and will also keep the bark at a more consistent temperature. Don't use brown paper tree wraps or black-colored guards as they absorb heat from the sun. The best time to put on a guard is in the fall, removing it in the spring after the last frost.
Being mindful of your landscape can help avoid these types of injuries. Consider using any buildings for protection or plant evergreens to the south to southwest of your Japanese Maple for additional shelter. If your tree does suffer a wound from sunscald or frost cracks, don’t panic! Trees have an incredible ability to seal their wounds. Through a process called compartmentalization, trees will cover the wound with tissue and produce new, healthy wood over the once-damaged area. They don’t exactly “heal” the wound but form new healthy tissue over it.
Consider Alternatives to Japanese Maples
If your property does not have a suitable location for a Japanese Maple, consider an alternative such as other East-Asian Maples hardy to zone 4. For example, Paperbark Maple (Acer griseum), Three-flower Maple (Acer triflorum), and Korean Maple (Acer pseudosieboldianum) are all wonderful alternatives that are more cold-hardy, and just as beautiful and unique.
As Maples interbreed so readily, there are hybrid Maples bred from crossing Zone 5 Japanese Maples with maples hardy to zone 4, resulting in a tree hardy to zone 4 with some of the sought-after ornamental characteristics of Japanese Maples.
Japanese x Korean maple hybrids are perhaps the most commonly seen, such as:
- Northern Glow (Acer pseudosieboldianum x palmatum ‘Hasselkus’), developed by Professor Ed Hasselkus in Madison, Wisconsin
- Arctic Jade (Acer psuedosiboldianum ‘Arctic Jade’)
- North Wind (Acer x pseudosieboldianum ‘North Wind’)
- Final Fire (Acer x pseudosieboldianum ‘Final Fire’)
Although there are other Japanese Maple hybrids hardy to zone 4, they are far less common than Korean Maple hybrids and include the Gingerbread Maple, which is a cross between Acer griseum, the Paperbark Maple, and Acer maximowiczianum, formally known as Acer nikoense, the Nikko maple.