Q.large elm tree peeling bark, leafing late
What is causing my beautiful 50 yr. old backyard shade elm to be losing its bark in lots of small chunks? Is it normal shedding or is there something attacking it? Also, why does it consistently leaf out much later than other elms in the neighborhood? Since it’s now late January, if it needs treatment, what would the treatment be and when would be the best time to do it? Or, if the tree is ok, what can I do to ensure continued good health?

Though it is normal for some types of trees to shed their bark. Some varieties of Elm do shed bark.
If this is new to your tree you need to investigate a bit further.
Is the tree suffering damage from rodents such as squirrels?
Is the tree under stress from weather or watering issues?
Are there other signs of disease or insects? Yellowing leaves, damage to leaves, leaf drop?
Elm trees are susceptible to several diseases with Dutch Elm disease being reported throughout the country.
I would encourage you to have the tree examined by a certified Arborist.
Here are several links for you with more information.
https://www.gardeningknowhow.com/ornamental/trees/tgen/peeling-bark-on-trees.htm
http://www.na.fs.fed.us/spfo/pubs/howtos/ht_ded/ht_ded.htm#symptoms
https://extension.psu.edu/pests/plant-diseases/all-fact-sheets/elm-diseases
http://www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/DISEASES/dutchelmdis.html