Meet Malus and Pyrus

Go anywhere in Boston in early spring and trees will shower you with white and pink blossoms. They decorate the crabapples (Malus) and pears (Pyrus), both groups belonging to the Rosaceae, or rose, family. As such, they share visible characteristics that make them hard to tell apart until you know what to look for. Both have 5-petaled flowers, are great sources for nectar and pollen, and share similar growth requirements. However, the crabapple tree flowers often display pink/red tones, have yellow anthers with green stigmas, are fragrant sweet smelling, and are loosely clustered on a branch. In contrast, the most common pear tree in Boston, the Callery pear (Pyrus calleryana) has flowers that are pure white, often bloom 1 week earlier than Malus, have red anthers, smell fishy and unpleasant, and grow in a tighter, more upright cluster on a branch. Curiously, pollinators tend to visit Malus flowers more frequently due to higher nectar sugar concentrations, while Pyrus produces higher volumes of lower-sugar nectar.

Although there are some native North American crabapple species (Malus coronaria in the northeast) most apple trees in the US come from introduced European and Asian stock. Indigenous Peoples used native crabapples as food and medicine but quickly adopted European seeds into their culture. The first American variety of apple, Roxbury Russet, emerged around 1635 in Boston and was bred primarily for cider production. Today, most crabapples dotting Boston streets are cultivars such as Sargent crabapple or Donald Wyman crabapple.

Pears are a completely introduced species to North America, but one with important roots in Boston. The most popular pear in the US dates to1799 when several European pear trees were planted in an estate in Roxbury, and a later owner, Enoch Bartlett thought the trees were his own discovery. He began distributing them under his own name, and the Bartlett pear became the standard in North America. Later, the Clapp family from Dorchester created a hybrid of the Bartlett and Flemish Beauty pears creating a new variety named Clapp Favorite Pear. A giant 12-foot-tall bronze Clapp Favorite pear sculpture pays homage to Dorchester’s agricultural history.

Chances are that you will be staring at a Callery pear (Pyrus calleryana) when exploring Boston schoolyards and neighborhoods. This is because Callery pear trees were very popular in the 1950’s and planted extensively in Boston and suburbs. Today, Callery pear trees are banned in the state due to its invasive nature, weak wood, foul smelling flowers and ability to displace native trees and altering soil composition. Ironically, it was the Arnold Arboretum that first introduced Pyrus calleryana to the US! Read about the Rise and Fall of the Ornamental Callery Pear Tree. It’s quite fascinating.

Outdoor Journal Activities

Find a crabapple, pear, cherry or hawthorn tree to observe. These are all part of the Rosaceae family and thus will have similar looking flowers. Make observational drawings of flower parts, and note scents, colors, size, and flower habit.
Ask permission to collect some flowers and press them between newsprint inside thick heavy books (or a plant press!) Add leaves too and label your finds so you can mount them later.
Spend some time observing how many and which types of pollinators visit your trees. Note also whether their pollen baskets are covered in pollen or if their behaviors indicate nectar foraging. Can you tell the difference?

Science Labs

Introduce flower dissection using members of the Rosaceae family. The distinct petals, stamen and pistils make them perfect exemplars for complete flowers. High school students can learn from the Interactive Virtual Flower Dissection Lab module.
Observe pollinator/flower interactions on crabapple vs. pear trees to gather data on flower preference. Start by learning about the power of pollinators. Then go outside to set up your field experiment.
Can your students design an experiment to test this statement: “Curiously, pollinators tend to visit Malus flowers more frequently due to higher nectar sugar concentrations, while Pyrus produces higher volumes of lower-sugar nectar.”

The Arboretum for Educators

Meet Malus and Pyrus