By: Natalie Hamilton
Gymnocladus dioicus, also known as the Kentucky coffeetree, is a commonly used shade and ornamental species. It is native throughout the northeast and central United States under USDA plant hardiness zones 3-8. Although it does not produce coffee beans, early settlers of Kentucky gave this tree its name as the beans it produces resemble those of coffee trees.
The Kentucky coffeetree can reach heights of up to 60-75 feet and has an upright and wide spreading canopy. This tree has a slow to moderate growth rate and displays beautiful bright yellow foliage in the autumn. This species can tolerate a wide range of site conditions and Is free of insect and disease problems. These reasons make it a good street or boulevard shade tree for urban areas. Kentucky coffeetrees have deeply furrowed dark brown bark that appears to peel in strips vertically along the tree. Female trees produce 5-10 inch long pods that contain hard leathery seeds, which are poisonous if ingested raw. This species also produces massive, opposite bi-pinnately compound leaves that are 3 feet by 2 feet long. These unique characteristics make the Kentucky coffeetree stand out as striking and aesthetically pleasing throughout all four seasons.
A cultivar is a variety of a plant that has been selected and bred for desirable traits. Current popular Kentucky coffeetree cultivars include Espresso, Prairie Titan, and Stately Manor. All three of these cultivars are male varieties and therefore do not produce seed pods, which some homeowners find undesirable. If you are interested in planting one of these cultivars in your own yard, know that the availability may be varied. Research may be required to find a nursery near you sells Kentucky coffeetrees.
- Espresso™ (Gymnocladus dioicus 'Espresso'): Male cultivar with oval or vase shaped branching spread
- Prairie Titan™ (Gymnocladus dioicus ‘J.C McDaniel'): Male cultivar with a more upright spreading branch habit. Introduced by the University of Illinois.
- Stately Manor (Gymnocladus dioicus 'Stately Manor'): Male cultivar with a narrow, upright form which may more desireable in compact urban spaces. Introduced by the University of Minnesota.
Germination and The Megafauna Theory
Scarification is a process of weakening the coat of a seed. Many seeds, including those of the Kentucky coffee tree, require scarification in order to trigger germination.The Kentucky coffeetrees seed coat is particularly tough and is often soaked in a weak acid in labs to enduce scarification. In nature when a seed pod and seed coat are extremely tough, large animals with strong jaws, such as an elephant or rhinoceros, naturally take care of this. The chewing, ingestion, and passage through the animal's digestive track acomplishes scarification. Today, however, there are no animals within the native range of the Kentucky coffeetree that are capable of doing this. This puzzling phenomenon has made scientists wonder how the Kentucky coffeetree has been able to survive naturally without human intervention. One theory is that the pods of the kentucky coffeetree were once eaten by extinct megafauna. Giant herbivorous mammals, such as the giant ground sloth, once roamed the North American landscape. Scientists believe this overlap in range makes it plausable that these now extinct animals were the ones to scarify and disperse the Kentucky coffeetree's seeds.
All photos and references are used for educational purposes only.
- Arbor Day Foundation. "Kentucky Coffeetree: Gymnocladus Dioicus." N.p., 2016. Web. 10 Jan. 2017. <http://bit.ly/2id3E6R>.
- Department of Horticulture. "Kentucky Coffeetree." University of Kentucky, 1 Nov. 2016. Web. 10 Jan. 2017. <http://bit.ly/2j21Yku>.
- ISU Forestry Extension. "Kentucky Coffeetree (Gymnocladus Dioicus)." Trees of Iowa: An Interactive Key. Iowa State University, 17 Aug. 2015. Web. 10 Jan. 2017. <http://bit.ly/2j2fUee>.
- Missouri Botanical Garden. "Gymnocladus Dioica." N.p., n.d. Web. 10 Jan. 2017. <http://bit.ly/1tjRC0W>.
- The Morton Arboretum. "Kentucky Coffeetree." N.p., n.d. Web. 10 Jan. 2017. <http://bit.ly/2j4IwEo>.
- Zaya, David N., and Henry F. Howe. The Anomalous Kentucky Coffeetree: Megafaunal Fruit Sinking to Extinction? (2009): n. pag. Oecologia. U.S. National Library of Medicine. Web. 20 Jan. 2017. <http://bit.ly/2jy0tZv>.
- Davis, Janet. Gymnocladus dioicus-Kentucky Coffeetree. n.d. Web. 4 Jan. 2017. http://bit.ly/2iQ5YCh
- Spencer’s Garden Center. Kentucky Coffee tree :(Gymnocladus Dioicus). n.d. Web. 4 Jan. 2017. http://bit.ly/2jah3kY
- Galvan, Jeff. Coffeetree, Kentucky – Trunk. 2016. Web. 4 Jan. 2017. http://bit.ly/2hRMWyF
- AQ Nature. Kentucky Coffee-Tree (Gymnocladus dioicus) Leaf Appearance. n.d. Web. Jan 4. 2017. http://bit.ly/2ibupt1
- Portrait of the Earth. Seed pods. n.d. Jan 4. 2017. http://bit.ly/2iEz340
- Denver Museum of Nature & Science. Giant Ground Sloth. Nov 30. 2010. Web. Jan 4. 2017. http://bit.ly/2iB8xKH
Just a few days before Halloween I had a unique and wonderful opportunity to share my passion for arboriculture with a group of Masters of Fine Arts students enrolled in the Nomad 9 MFA program at the Hartford Art School.
The Nomad 9 group had just wrapped up a week-long residency with my co-host and Friendship Forest originator Amanda Lovelee; Friendship Forest was the last stop on their Minnesota visit. Friendship Forest was planted this June in cooperation with City of Saint Paul, and Mississippi Park Connections and provided ample opportunities to discus the art of tree care with these students. We spent the day talking about pruning young trees, the complex relationship between trees and the soil, and the important interactions that exist between trees and humans in urban and community forests.
Looking towards Downtown Saint Paul from within the Friendship Forest
Friendship Forest begins just east of the Lafayette Bridge at Lower Landing Park. The Mississippi River provided water for our new trees planted with the Nomad 9 students.
The morning started out with a overview of tree biology and basic tutorial on tree pruning. Many of the smaller Kentucky coffeetree, river birch, and cottonwood have grown considerably and required some basic developmental pruning to get them growing in the right direction. We closed out the day with planting a few trees to replace some river birch that had died since planting. In the spirit of the original planting, these trees received new Friendship Forest tags adorned with the unique Nomad 9 rabbit logo.
Carol, Director of the Nomad 9 MFA program, tries her hand at pruning a young Kentucky coffeetree.
Bri, an Undergraduate Research Assistant on Team Tree works with Carol and two Nomad 9 students to plant a new river birch. This project utilized the grow tube method using Plantra’s SunFlex system and Greenwell Water Savers.
Friendship Forest tags provide information on each tree with the names of the planters and their name for the tree!
In all I found this event and the interaction with this group of students refreshing, inspiring, and thoroughly enjoyable. Radical creativity, fine arts, and arboriculture are a good mix!
A group of students enjoying a moment in the sun with their newly planted river birch.
by Nick Perry
When you see or hear the word autumn, what is the first image you have? Many people immediately think of the spectacular color changes in the foliage. The magnificent reds, yellows and oranges can really be prominent during sunny autumn days.
This week’s “Tree of the Week” does not disappoint when it comes to displaying brilliant fall coloring.
The Highland Park Maple, Acer grandidentatum x saccharum ‘Hipzam’, is part of the Sugar Maple family and is native to North America. It is classified as a Zone 4 tree on the USDA hardiness map and can be grown in the majority of Minnesota.
The Highland Park Maple is not a very large tree in size. It can grow between 30 and 50 feet in height and its spread can vary from 20 to 25 feet. With a pyramidal growth habit, it can be used in both group plantings or as a stand-alone accent tree in a residential yard. It requires full sunlight and grows at a medium rate. Because it can handle adverse growing conditions, this maple may be able to grow where other similar maples do not fare as well. The capability to tolerate dry soils and urban pollution allows it to grow in commercial and residential environments. The ability to resist pests and diseases also add to its allure. It shouldn’t be considered for boulevard plantings, as it does not fare well in saline soils and its lateral branches typically arise roughly 78 feet off the ground.
The tree does not produce any showy flowers or fruit. It does, however, have very nice foliage. The leaves are sturdy and tatterproof. In the spring and summer, they are a rich dark green. In the fall, they begin to change color producing gorgeous reds, yellows and oranges.
Young, red branches also add an attractive element to the landscape throughout the year. The red branches can really look picturesque against the freshly fallen snow.
The University of Minnesota has successfully grown the Highland Park Maple species at their St. Paul field location. They will provide several of these specimens to local areas including the City of St. Paul and the Minneapolis Park and Recreation Board.
- Plant Finder: Highland Park Bigtooth Maple. (n.d.). Chalet Nursery website. Retrieved from: http://plants.chaletnursery.com/12120004/Plant/11343/Highland_Park_Bigtooth_Maple
- The Tree Farm: Highland Park Bigtooth Maple. (2010). The Tree Farm website. Retrieved from: http://www.thetreefarm.com/maple-bigtooth-highland-park
- Acer grandidentata. ‘Highland Park’ Bigtooth Maple. (n.d.). Robinson Nursery website. Retrieved from http://www.robinsonnursery.com/wpcontent/uploads/2012/02/Acergrand.HighlandPark.pdf
- As Tough As Nails. (2010). Lake County Nursery website. Retrieved from: http://www.lakecountynursery.com/newsroomprElaeagnusTitanAcerHighlandPark.html
- Photo Courtesy of Willoway Nurseries, Inc. Willoway Nurseries Inc. Acer grandidentatum ‘Hipazam’ – Highland Park Maple. 2015. Willoway Nurseries inc. Avon, OH. Willoway Marketing. Web. 23 October, 2015. Retrieved from: http://www.willowaymarketing.com/index.cfm?fuseaction=plants.plantDetail&plant_id=101277
by Natalie Hamilton
Photo courtesy of the city of Portland Oregon Parks and Recreation Department
This week’s tree is Cercidiphyllum japonicum, or the katsura tree. Although it is native to Japan and China, it does well in areas designated under USDA plant hardiness zones 4b-8. This means it would thrive in our cooler midwestern climate. These trees typically grow to around 40-60 feet tall but have been known to reach heights of 100 feet tall or more in special circumstances. Katsuras prefer moist soil and should be planted in areas where they can receive partial to full sun.
Photo courtesy of Heritage Seedlings & Liners
The katsura is known to be a moderate-to-fast growing tree with a pyramidal to a more arched form at maturity. This tree has brilliant autumn foliage, making it a particularly attractive ornamental choice. The leaves can be shades of yellow-gold, bright orange, and deep red. It’s said to have a spicy, almost brown sugar, scent before the leaves drop for winter. Living in a state where salt is used on the road throughout the winter months can make plant and tree selections burdensome. Many plants suffer dieback injury and stunted growth by overexposure to salt spray. This tree, however, is salt tolerant, making it even more appealing.
In 2015 the UFORE lab received its first tree nursery stock. Soon after, we planted a trial in Minneapolis to test and become more familiar with the katsura’s hardiness and growth habit in our local area. A new trial will be planted this year in downtown St. Paul. We are continuously producing our own seedlings from seeds, which will be used for grow tube trials.
Photo courtesy of Jean-Pol Grandmont
An article called “The Five Percent Solution,” written by South Dakota University’s Professor John Ball, discusses selecting climatic adaptive species in the north central region of the United States, and stresses the importance of expanding species diversity. The katsura tree would be an excellent example of a tree that would broaden Minnesota’s species diversity, as well as make a great rendition to any landscaped area or home owners yard as a beautiful ornamental shade tree.
- Kelly, Bridget. “What Is a Katsura Tree?” Home Guides. Demand Media, n.d. Web. 10 Feb. 2016. <http://sfg.ly/1nZdQTt>.
- Grant, Bonnie L. “Katsura Tree Care – Information About Growing Katsura Trees.” Gardening Know How, 25 May 2014. Web. 10 Feb. 2016. <http://bit.ly/1Q9fWg5>.
- “Katsura Tree.” Trees & Plants. The Morton Arboretum, n.d. Web. 10 Feb. 2016. <http://bit.ly/1PDlHNK>.
- Grandmont, Jean-Pol. Cercidiphyllum Japonicum. 2007. Web. 10 Feb. 2016. <http://bit.ly/1LhtDCv>.
- Heritage Seedlings & Liners. Katsura Tree. N.d. Cercidiphyllum Japonicum. Web. 10 Feb. 2016. <http://bit.ly/1V4gAtA>.
- Parks and Recreation Department of Portland Oregon. Tree#159. N.d. Cercidiphyllum Japonicum. Web. 10 Feb. 2016. <http://bit.ly/1T84sIL>.
by Nick Perry
When it comes to producing brilliant fall foliage, few trees can compete with the Sugar Maple. A small maple, native to the Rocky Mountains, definitely gives the Sugar Maple a run for its money. This week’s tree of the week is the Rocky Mountain Glow Maple, Acer grandidentatum ‘Schmidt’. It is a variety of the Bigtooth Maple and was introduced by J. Frank Schmidt Nurseries.
The Glow maple consists of Bigtooth Maple stock grafted onto Sugar Maple rootstock. When mature, it is smaller and more compact than the Sugar Maple. The mature height ranges between 20’ to 30’ and the spread reaches between 15’ to 30’. The growth rate is slow to medium and the canopy develops into a tight, oval shape.
The leaves of the Glow Maple resemble Sugar Maple leaves, but are smaller in size. In the spring and summer they are a rich, dark green. In the fall, they begin to change color producing vibrant reds, yellows and oranges and the tree can appear to “glow”. The trunk and young branches of the developing tree are red and aesthetically add to the landscape year-round. Mature bark turns gray and develops long, irregular furrows and plates that also add to the visual aesthetics of the tree. Spring flowers are not showy and, when fertilized, produce a common samara.
Growing the Glow Maple requires partial to full-sun. Though it can grow in partial shade, it thrives best in full-sun locations. Soil conditions are also an important factor to consider. Soils need to be moderately moist and the roots need to be occasionally deep-soaked to produce healthy stock. The hardiness of the Glow Maple is zone 3, meaning it can tolerate extremely cold soils.
Issues concerning the Glow Maple are minimum, but include chlorosis, sun-scald and the development of decay fungi. Simply growing the maple in the correct landscape and keeping it healthy can eliminate most of these common issues.
Site locations need to be considered first before planting this maple. Planting on streets and boulevards should be avoided for several reasons, including the size of the mature tree, the susceptibility to soil compaction and the exposure to deicing salts. Because it tolerates other urban pollutants, this tree works well in residential yards and city parks. It can be used as a stand-alone specimen or in a group of multi-stemmed trees to provide a vegetative screen.
The University of Minnesota is currently producing the Rocky Mountain Glow Maple at their St. Paul research nursery. Though in production, the tree still has yet to be engaged in replicated trials or tested for regional adaptability.
- The Tree Farm. Rocky Mountain Glow Bigtooth Maple.(2010). Arbotanics,Inc.dba.Retrieved from: http://www.thetreefarm.com/maple-rocky-mountain-glow-bigtooth
- J.Frank Schmidt & Sons Co. Acer grandidentatum, Rocky Mountain Glow Maple.(2015).J.Frank Schmidt & Sons Co. Retrieved from: http://www.jfschmidt.com/introductions/rockymtnglow/index.html
- Conservation Garden Park. Rocky Mountain Glow Maple. (2015). Jordan Valley Conservation Gardens and Jordan Valley Water Conservancy District Website. Retrieved from http://conservationgardenpark.org/plants/1152/rocky-mountain-glow-maple/
- Frank Schmidt & Sons Co. JFS Introductions, Acer grandidentatum ‘Schmidt’ Rocky Mountain Glow Maple. (2015). J. Frank Schmidt & Sons Co. Website. Retrieved from http://www.jfschmidt.com/introductions/rockymtnglow/index.html
- Farmington Gardens. Maples-The Smaller Varieties. (2011). Farmington Gardens Website. Retrieved from http://www.farmingtongardens.com/pdf/infostation/50_maples_smaller.pdf