In addition to the early appearance of leaves, bush honeysuckle can be identified by the opposite branching pattern of the twigs and leaves (most of our native shrubs are alternate).
When walking through the forest sometimes you run across a tree with a strange lump, almost like a tumor. These woody outgrowths are known as burls (also known as burrs). No one is entirely certain what causes them, but it is believed that most are triggered when the tree undergoes some sort of stress - from certain types of mold or insect infestations, physical damage, and possibly genetic susceptibility. Some burls can grow quite large, and the wood is prized by artists and furniture makers for the unique and beautiful woodgrain patterns. The bark of the Cork Elm (Ulmus thomasii) is squishy, and indeed, very corklike! The bark grows in layers, typical of most elm bark. According to wikipedia, the Cork Elm is susceptible to Dutch Elm Disease, which may explain why we only seem to find a few small trees in the park.
If you're a tree hugger by nature, you might want to consider giving this tree a friendly, careful pat instead! These impressive thorny growths are found on the Honey Locust tree (Gleditsia triacanthos), making it a very easy tree to identify, even in the winter. The "honey" the tree is named for comes from the sweet pulp of the long bean pods the tree produces in fall, used for food and even fermented into beer by Native Americans. The pulp of the Black Locust tree bean pod is toxic, so be sure you have the right tree if you ever decide to taste it. Thornless varieties of the Honey Locust are often sold in plant nurseries for landscaping.