This year we're teaming up again with Saint Paul Parks & Recreation to add a few more flowering cherry trees at the Mannheimer Memorial in historic Como Park.

Last year, we had the great honor of taking care of the Spring Wonder flowering cherries (Prunus sargentii 'Hokkaido Normandal') prior to the planting that celebrated the 100th Anniversary of the original donation to the United States from Japan in 1912.   

I finally got our stereoscope linked up with our digital camera and thought to share some VERY close up photos from our flowering cherry collection.  Photos like this really help me appreciate the wonder of spring and how great and beautiful things are possible from such simple beginnings!

Kwanzan (Prunus serrulata 'Kwanzan')

Yoshino (Prunus x yedoensis)

Pink Flair (Prunus sargentii 'JFS-KW58')
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Check out this neat time-lapse video of our elm grafting process! Created by our very own J.W. Fillmore...and featuring American elm roostocks from our friends at Three Rivers Parks District Nursery.

Have you heard of Prairie Horizon Manchurian alder?  Not many have, but Minneapolis Park & Recreation Board got a big dose last fall during the installation of a new research project in the Armatage neighborhood in southwest Minneapolis.

Prairie Horizon cut its teeth on the tough and dry plains at NDSU's woody plant breeding program led by Dr. Dale Hermann (ret.)  We've had some great previous success in Armatage with Prairie Horizon, so we decided it was time for a little expansion.

We took Prairie Horizon grown in both the gravel bed and RootTrapper fabric containers and planted them in typical Minneapolis boulevard conditions with different combinations of SylvaSoil (an organic compost product) as an amendment.

Armatage is known for its high concentration of ash, so being prepared for potential losses due to EAB is really important.  With results from this research we hope to find more trees that will fill open planting sites and create soil conditions that will enhance their long-term survival and establishment.

See above and below for a photo-essay of my days entrenched with the arborists of MPRB!

Last fall I had the opportunity to join Mr. Don Willeke in observing the removal of a large 'Iowa State' American elm at his neighbor's house in the Dean Park area of Minneapolis. This large tree was planted in 1978, shortly after Don grafted it onto a wild American elm seedling.  Unfortunately, the tree had developed major defects over the years (it had already been cabled and braced) and required removal for safety purposes. 

Don is a local elm aficionado and has been "speaking for the trees" since the 1970s. He has been my host on many visits to the forest of elm trees (amongst other species) in and around his Dean Park home.

'Iowa State' was discovered and screened by Prof. Sandy McNabb at Iowa State University from the late 1960s to early 1970s where it proved to be quite resistant to Dutch elm disease (DED) when inoculated with the fungus. While not widely released (at least to my knowledge) this tree remains an important reminder of those lucky escapes - native American elms with high tolerance to DED. Unfortunately, the structure of this tree is less than ideal as it has a tendency to form weak branch unions due to inclusions and very acute angles of attachment.

In my ongoing efforts to make-lemonade-outta-lemons I worked with Don and Jay Linn from Log and Limbs Company (who was performing the removal) to collect some prime cuttings material for cloning of this now rare tree.  

By the end of the removal process Don and I were able to collect some vigorous vegetative shoots from the very top of the tree, which I brought back to the University for propagation and inclusion into our elm program.

Now, weeks later, I transplanted some of the first rooted cuttings of 'Iowa State' and can now add this tree to the growing collection of elms at the University of Minnesota.

Plants are also slated for distribution to the USDA National Arboretum in Maryland for inclusion into their continuing work on the American elm.

This December Jonathon and I (Greg) trekked out around Minneapolis collecting cuttings for asexual propagation for the Heritage project and came across this champion black willow (Salix nigra). Willow is considered to be a short lived tree that is prone to decay and failure because it grows too quickly for its own good. That is a good thing if you need a large tree fast but not if you want a tree that will last longer than you. This champion willow is located right across from the main parking lot of Lake Nokomis by field #5 if you care to see it up close. The circumference of the trunk is 379 inches and it stands 70ft. tall with an average canopy spread of 73.5ft! What a monster!

Jonathon Standing IN the monster!

Even with decay regularly pruned out this tree is still huge!

For the tree of the week, I chose the Minneapolis Heritage Horse Chestnut (Aesculus hippocastanum). This is the largest Horse Chestnut in the city, and it is right in front of Folwell hall on East Bank Campus! I would walk right by this tree every day, and until recently never took the time to notice it. It used to have another similar Horse Chestnut across the sidewalk, but that has been replaced with a new tree.

Horse Chestnuts are native to Greece and Albania, but are now widely cultivated in parks and urban areas. They grow very slowly, but can reach 50' to 75' on average, with some up to 100'. They grow taller than they are wide, and have a dome shaped or oval final form. The name comes from their large, hard seeds, that were once believed to cure horse chest ailments, but have since been proven to be poisonous. The seeds, which can be messy, and dangerous if ingested, along with their tendency to grow to massive size are the main concern when planting a horse chestnut.

Despite this, they enjoy enormous popularity.They are hardy trees, in zone 3, making them great candidates for Minneapolis. They also do well in most soil types, preferring moist roomy soil. The trees have showy white, yellow, and red flowers and rich foliage.

Other than this heritage sample, the Horse Chestnut has enjoyed popularity as a common choice for German beer gardens. It was a common choice because of its wide deep shade, that kept patrons cool. Also, the "Anne Frank Tree", which Anne Frank mentions in her diary multiple times, was a Horse Chestnut. It was locate in the middle of Amsterdam. This tree sadly blew over in 2010, weighting in at 27 metric tons.

Many of my friends assume that I am out of the job now that the snow has fallen, and the 

days are short and cold. Although we don't get outside as much anymore, there is still a lot of work for team tree over the winter months. Recently, we drove out to St. Paul to take data on the High Bridge dog park. There is an earlier article that talks about the dog park in more detail, but it is basically a remidation site where we planted groups of 1 1/2" caliper trees on the site of a former rail yard for a coal plant. The site is a difficult place for trees, with poor soil conditions, and of course, lots of dogs, who may or may not be nice to the trees we planted. We have been taking data for awhile on how well they are growing to see what varieties do well in the adverse conditions.

During our check up on the trees, we were going to collect data on caliper and take photos of 

the trees. 

Sadly, many of the trees have lost all their cambium at some points, which will most likely kill the trees. Chad said that when he originally checked the site out, the trees in the surrounding area showed signs of damage from critters, and there was probably a lot of them living in the area.

The remaining trees that survive the winter will make it to the 2" caliper mark, where the bark usually will become hard and inedible. Also, there was generally less damage on Catalpa, Birch, and Alder than other varieties. 

Team Tree met up with some Saint Paul Forestry after our initial visit and wrapped the stems, so some of the trees will make it to spring!

We say goodbye to another member of Team Tree. Greg was the most senior member of team

 tree, and was a very valuable addition. He was the only one who could give Chad a run for his money on Skiddy, has extensive horticultural knowledge, and lots of nursery experience. Greg graduated with a degree in horticulture and is working at a landcare company in the southwest metro area.

Greg, you will be missed. The best of luck in your future endevors

There is a lot of work we have to do around the nursery to get ready for winter. The trees we 

grow expect, and rely on winter to come, but they are also used to being under the ground, away from the harsh temperatures of the surface during winter. They are also vunerable to animals who will nibble away their cambium, which, if it gets bad enough, will kill the trees. If a tree is small enough, animals will leave you with only a frayed stump. 

When planning to keep trees alive over winter, you need to keep these concerns in mind: to keep them protected from animals, and also to keep them in enough mass that the roots don't freeze and kill the plant. In planning for this, you need to take into account the amount of snow you will get. If you put a 6 inch wrap on a tree and there is 2 feet of snow, the wrap is going to be a foot and a half under, leaving the tree exposed. For our nursery stock, we placed as many as we could in the pot-in-pot section, and for the rest, we packed them in with mulch and then wrapped the stems.

This week's tree of the week is the London Plane Tree (Platanus x acerifolia). The London Plane Tree is a stately shade tree growing to a height of 70 feet tall. The mature bark is a stunning pale grey with exfoliating brown bark. The leaves resemble the look of a maple having a palmately lobed leaf. However, unlike a maple leaf, the London Plane Tree has a fussy back, giving it a unique character.

Being a zone 5 tree, The London Plane Tree is not commonly seen in Minnesota as it is not hardy to the northern climate. However, there are a few London Plane Trees scattered throughout St. Paul and Minneapolis. The slightly warmer temperature of the cities is often just enough for the London Plane Tree to survive the harsh Minnesota winter.

In the team tree fields, we have three varieties of London Plane Tree, Exclamation!™, Columbia, and Bloodgood. All three varieties grew extremely well this season! It was exciting to see the trees grow from small 4-6 foot whips to a sizable 1" caliper trees (left image). This fall, we dug out most the London Plane Trees to prepare to plant in root trapper containers next spring!

The image bellow shows two of the four rows of London Plane Tree at the nursery. The lush, 12 foot strips of grass like plants growing in between the rows of trees are cover crop that team tree uses in all fields to keep the soil as healthy as our trees. The cover crop is a mixture of millet and buckwheat, both fast growing plants. The cover crop is used to maintain moisture in soil, reduce weed population, prevent wind erosion, and finally, increase soil organic matter. Often times, nurseries keep the soil bare by continuously spraying for weeds throughout the season to reduce the competition for resources. However, the benefit cover crop provides for the soil far out weights the marginal decreased caliper growth.

The vigorous growth of the London Plane Tree is quite typical for the tree. The London Plane Tree is often used as street trees in warmer climates due to the vigorous growth and ability to withstand high compaction and atmospheric pollution. The number of tough tree species for urban situations is becoming less with the loss of American elm to Dutch elm disease and the more recent loss of Ash species to emerald ash borer. Both American elm and ash trees were extremely common street trees due to similar tough qualities the London Plane Tree has. With fewer and fewer street trees to withstand the tough street conditions, it is important to test the winter hardiness of different tough trees like team tree is doing with the London Plane Tree.