The Malus Collection

By Jon Peter, Curator & Plant Records Manager, Royal Botanical Gardens

The genus Malus is a member of the Rose Family (Rosaceae) and includes edible apples, ornamental crabapples, and wild species apples/crabapples. It is a diverse group of trees and shrubs represented globally by 30 – 55 species which are native throughout the northern hemisphere. There are also hundreds of introduced named cultivars.

Crabapples are durable, small trees or large shrubs that work well in urban landscapes. Crabapples will thrive in a variety of soil types (preference for well-drained) in full sun locations. Generally, they will tolerate the cold winters and hot, dry summers. Crabapples have been selected and hybridized for centuries to improve flowering characteristics, fruit colour, size, and quality, for increased hardiness and most importantly for disease resistance. As with most members of the Rose Family, disease is often an issue.

At RBG, our Malus collection focuses on the ornamental crabapples and not domesticated culinary apples. Crabapples flower in mid spring in a variety of colours, sizes, and fragrances.  They develop small fruits which ripen between July and November, with some fruits persisting on the trees until the following spring. By definition, Malus are considered crabapples if they produce fruits from ¼” to 2” in size.

Crabapples have been planted in RBG’s gardens since 1930 when a Malus baccata (RBG accession 30035*A) was planted in the Rock Garden. Our official Malus collection is concentrated at the Arboretum, near the Nature Interpretive Centre, continuing north towards the propagation facility. This was the first collection to be initiated in the Arboretum with 55 types acquired in 1954 and laid out and planted in spring of 1956.

Although our Malus collection may seem like a random sampling of beautiful trees, there is some logic behind the arrangement of plantings. When the collection was started, it was laid out in sections with avenues running through it, in a similar design to the rest of the Arboretum (see map from 1968). The areas were planted based on where the crabapples originated from (‘American Crabapples’, ‘Chinese Crabapples’ and ‘European Crabapples’). Over time, the objective evolved to feature groups of species and cultivars with the same form (vase shape, tree form, shrub form, upright/columnar and weeping forms) close to one another. There are also clusters of trees focused on characteristics like ‘good fruiting’ and ‘purple foliage’. Lastly, there is an educational goal to connect to visitors with recommendations for their own landscapes by featuring cultivars ‘selected/hybridized in Canada’, for ‘recent introductions’ and a grouping at the front of the collection featuring cultivars which were ‘currently recommended’ (see map from 2016). Although the avenues have not been preserved, planting in the collection still follows the guidelines previously set.

We had significant plantings added to this collection in each decade from 1950s through the early 1990s then additions dropped off until more recently. In the previous two seasons (2018-2019), this collection saw its most growth since the early 1980’s with a total of 26 trees representing 16 taxa (all new to the collection) planted in the appropriate arrangements. Currently, the Malus collection features 186 individual trees, representing 120 accessions and 84 taxa (unique types) across all garden spaces. The concentrated Malus collection in the Arboretum features 103 individual trees, representing 76 accessions and 64 taxa.

Although most crabapples are not native to Ontario, you will find flowering specimens buzzing with pollinators taking advantage of the pollen and nectar resources. The fruits will also attract wildlife to your garden, especially smaller fruits which are easy to consume by birds like the American Robin (Turdus migratorius). Crabapple fruits which persist on the trees into winter become more palatable after several freeze thaw cycles and are a favourite source of food for Blue Jays (Cyanocitta cristata), Cedar Waxwings (Bombycilla cedrorum), and even some woodpeckers.

This historical collection can be categorized by RBG Living Collections Policy as a Horticultural, Taxonomic, Morphological and Economic Collection and is relevant to Science, Education and Horticulture in every way. It is a pleasure to explore during spring flowering, summer growth, and fall/winter fruiting, and is an amazing resource of beautiful trees and shrubs at any time of year.