The rose family Rosaceae is a globally recognized plant family, celebrated for its beautiful flowers and edible fruits. If you’ve ever enjoyed the crisp bite of an apple, the sweet fragrance of a rose, or the juicy burst of a strawberry, you’ve experienced the bounty of the Rosaceae family. This diverse family encompasses a wide array of plants, from flowering shrubs and trees to ground-hugging herbs, all sharing a set of common botanical characteristics. Understanding these features is key to identifying members of the rose family Rosaceae in gardens, orchards, and wild landscapes.
Identifying the Rose Family: Key Characteristics
Plants belonging to the rose family Rosaceae exhibit several distinctive traits that aid in their identification. While variations exist across the family’s numerous genera and species, certain floral and leaf structures are consistently observed.
Leaves: Rosaceae leaves are typically alternate along the stem, meaning they don’t grow directly opposite each other. Their form is highly variable, ranging from simple leaves to compound leaves that are trifoliate (with three leaflets), palmate (leaflets radiating from a central point), or pinnate (leaflets arranged along a central axis). A common feature across these leaf types is the frequently oval shape of the whole leaf or individual leaflets, often adorned with serrated or toothed edges. This serration pattern serves as a valuable secondary characteristic for recognizing the rose family Rosaceae.
Flowers: The flowers of the rose family Rosaceae are generally radially symmetrical and often visually striking. A typical flower will have 5 separate sepals and 5 petals, although some species may exhibit variations with 3 to 10 sepals and petals. The stamen count is a crucial identifier: there are always at least 5 stamens, but many species boast numerous stamens, often in multiples of five. The center of the flower, the pistil, can be structured in two main ways within the rose family Rosaceae. Many, especially in the Rose subfamily, have multiple simple pistils, creating a fuzzy central cluster. Alternatively, the pistils may be fused at their base, with separate styles emerging, forming a compound pistil with multiple styles. Both configurations result in a characteristic fuzzy center surrounded by a ring of stamens.
Fruits: The rose family Rosaceae is remarkably diverse in its fruit production. Members of this family produce a wide range of fruit types, from fleshy fruits we commonly consume to dry seeds, capsules, or follicles. This fruit diversity is a testament to the evolutionary adaptability of the family.
Globally, the rose family Rosaceae is substantial, comprising approximately 100 genera and 3,000 species. In North America alone, around 50 genera are represented. Beyond their ornamental appeal, the rose family Rosaceae is economically significant, providing numerous edible fruits. Many Rosaceae plants contain tannins, contributing to astringent properties. It’s also important to note that some species contain cyanide compounds in their leaves and fruits.
A Brief History of Rosaceae Classification
In the early 20th century, botanical classifications underwent revisions, leading to the reclassification of the Spirea, Plum, and Apple families as subfamilies within the broader rose family Rosaceae. This change, while scientifically driven, humorously prompted the poet Robert Frost to reflect on the evolving nature of botanical understanding, questioning what might “next prove a rose.”
Modern taxonomy has further refined the classification within the rose family Rosaceae, determining that the Spiraea, Plum, and Apple groups were not genetically distinct enough to warrant separate subfamilies. They are now more accurately combined into a single subfamily known as the Almond subfamily, Amygdaloideae.
When identifying a plant specimen, understanding these subfamilies within the rose family Rosaceae is a helpful step in narrowing down identification possibilities.
Key Identification Features: 5 sepals and 5 petals, numerous stamens, oval, serrated leaves.
Subfamilies of the Rose Family
The rose family Rosaceae is organized into several subfamilies, each with its own set of characteristics. Here, we explore three key subfamilies: the Rose Subfamily (Rosoideae), the Dryad Subfamily (Dryadoideae), and the Almond Subfamily (Amygdaloideae), which includes the Spiraea, Plum, and Apple groups.
Rose Subfamily: Rosoideae
The Rose Subfamily (Rosoideae) is characterized by members with numerous stamens and numerous styles.
Rosa woodsii. Wood’s Rose, showcasing the numerous stamens characteristic of the Rose Subfamily.
Flowers in the Rosoideae subfamily often feature a slightly domed receptacle beneath the pistils. Some species might superficially resemble Buttercups (Ranunculaceae) due to their numerous stamens and simple pistils attached to a cone-like receptacle. However, a key distinguishing feature is the presence of stipules at the base of leaves in the Rose subfamily, which are absent in Buttercups. Stipules are small, leaf-like appendages found at the base of leaf stems.
Plants of the Rose subfamily have multiple separate pistils (sometimes united at the base). Botanically, each pistil’s ovary develops into an individual fruit. In most roses, this fruit is a dry seed called an achene. However, the Rosoideae subfamily also presents fascinating examples of false fruits. In a rose hip, for instance, each ovary produces a dry seed, but these seeds are enclosed within a fleshy receptacle that resembles a fleshy ovary. Strawberries exhibit a similar, yet inverted structure, with dry seeds embedded on the surface of a fleshy receptacle. Raspberries, in contrast, produce true fleshy fruits; the ovary of each simple pistil swells to form an aggregate fruit covering a domed receptacle.
| Rosa acicularis. Prickly Rose. | Rosa acicularis. Prickly Rose. |
|---|---|
| Rosa woodsii. Wood’s Rose. | Rosa woodsii. Wood’s Rose. |
| Rosa sp. Wild Rose Hips. Pony, Montana. | Rosa gymnocarpa. Baldhip Rose. Fruits drop sepals, unlike other species. |
| Fragaria vesca. Wild Strawberry. | Frageria virginiana. Wild Strawberry. |
| Fragaria sp. Wild Strawberries. | Fragaria sp. Wild Strawberries. |
| [Duchesnea indica (Potentilla indica). Mock Strawberry with yellow flowers, introduced from Asia. | |
| Fallugia paradoxa. Apache Plume, native to the American Southwest. | Geum macrophyllum. Yellow Avens. |
| Geum triflorum. Prairie Smoke. | Geum triflorum. Prairie Smoke. |
| Potentilla anserina. Silverweed Cinquefoil, Harrison Lake, Montana. | Potentilla glandulosa. Sticky Cinquefoil. |
| Potentilla recta. Sulphur Cinquefoil, introduced and invasive. | Potentilla recta. Sulphur Cinquefoil. |
| Pentaphylloides floribunda (Potentilla fruticosa) Shrubby Cinquefoil, Tobacco Root Mountains, Montana. | Pentaphylloides floribunda (Potentilla fruticosa) Shrubby Cinquefoil. |
| Rubus parviflorus. Thimble Berry. | Rubus parviflorus. Thimble Berry fruit. |
| Rubus armeniacus (Rubus discolor). Himalayan Blackberry. | Rubus armeniacus (Rubus discolor). Himalayan Blackberry. |
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| Rubus leucodermis. Blackcap Raspberry. | Rubus laciniatus. Cutleaf Evergreen Blackberry. |
| Rubus idaeus. Raspberry. | Rubus spectabilis. Salmonberry. |
Dryad Subfamily: Dryadoideae
In the Dryad Subfamily (Dryadoideae), the ovary of the flowers matures into a dry seed, or achene.
Dryas octopetala. Mountain Avens, showcasing the feathery plumes on the seeds, a Dryad Subfamily characteristic.
A defining feature of this subfamily is the persistent style, which remains attached to the ovary and typically develops into a feathery plume connected to each seed. This feathery plume characteristic is also observed in Geum triflorum and Fallugia paradoxa within the Rose subfamily.
Dryads share an ecological trait with members of the Pea family (Fabaceae): they engage in a symbiotic relationship with nitrogen-fixing bacteria in the soil. These bacteria reside in root nodules, converting atmospheric nitrogen into a form usable by the plants. In return, the plants provide sugars to the bacteria, produced through photosynthesis.
| Dryas octopetala. Mountain Avens. | Dryas octopetala. Mountain Avens, an alpine flower. |
|---|---|
| Cercocarpus montanus. Mountain Mahogany. | Cercocarpus montanus. Mountain Mahogany, photographed in Red Rocks Park, Colorado, common in the Rocky Mountains. |
| Purshia tridentata. Bitterbrush. | Purshia tridentata. Bitterbrush. |
Almond Subfamily: Amygdaloideae – Spiraeas, Plums, and Apples
The Almond Subfamily (Amygdaloideae) represents a consolidation of the former Spiraea, Plum, and Apple subfamilies.
Spiraea betulifolia. Birch Leaf Spiraea, a representative of the Spiraea group within the Almond Subfamily.
Genetic research revealed overlaps between these groups, leading to their combination. While some genera were previously classified as Spiraeas, they showed closer genetic links to Plums or Apples. Despite this reclassification, the traditional groupings of Spiraeas, Plums, and Apples remain practically useful for plant identification.
Spiraea Group: Spiraea-type plants are predominantly shrubs, known for their dense, foamy clusters of small white or pink flowers. Stamens often extend beyond the petals, adding to their delicate appearance. Unlike the Rose subfamily, Spiraea group plants lack stipules on their leaves. The ovary is superior, with 2 to 5 (sometimes 1 to 12) simple pistils that may be partially fused at the base. Fruits in this group vary and include capsules, follicles (dry fruits splitting along a seam), and occasionally achenes.
| Spiraea betulifolia. Birch Leaf Spiraea. | Spiraea betulifolia. Birch Leaf Spirea, Tobacco Root Mountains, Montana. |
|---|---|
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| Spiraea douglasii. Western Spiraea. | Douglas spirea: Spiraea douglasii. Western spirea, native to western North America, photographed as an introduced plant in Sweden. |
| Physocarpus malvaceus. Ninebark. | Physocarpus malvaceus. Ninebark, a common shrub in Rocky Mountain forests. |
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Plum Group: The Plum group within Amygdaloideae includes plums, cherries, apricots, peaches, nectarines, and almonds, all classified under the genus Prunus.
Prunus virginiana. Chokecherry, a member of the Plum group within the Almond Subfamily.
In most Prunus species, we consume the fleshy fruit and discard the pit. However, in almonds (P. dulcis), we eat the nut inside the pit and discard the fleshy outer fruit. The ovary is mostly or entirely superior and typically consists of a single carpel (unicarpellate), forming a single chamber that matures into a drupe – a fleshy fruit with a stony seed, the pit. A characteristic “seam” on one side of the fruit and the almond-like pit inside are hallmark features of Prunus and its close relatives.
While technically edible, the fruits and nuts of Prunus species contain amygdalin in their nuts, a glycoside that breaks down into benzaldehyde and cyanide. Benzaldehyde provides the bitter almond flavor often used in cooking. The bitterness level is a good indicator of amygdalin concentration in the raw nut. Amygdalin, also known as laetrile or Vitamin B17, is considered beneficial in small doses, but excessive consumption can lead to cyanide poisoning. Cyanide disrupts cellular oxygen utilization, causing asphyxiation at a cellular level. Cooking, drying, or oxidation processes can neutralize the cyanide, making the nut inside the pit safe to eat.
| Prunus virginiana. Chokecherry. | Prunus virginiana. Picking Chokecherries, Twisp, Washington. |
|---|---|
| Prunus mahaleb. Mahaleb Cherry. | Prunus mahaleb. Mahaleb Cherry, Twisp, Washington. |
| Prunus tomentosa. Nanking Cherry. | Prunus tomentosa. Nanking Cherry. |
| Prunus americana. American Wild Plum. | Prunus americana. American Wild Plum. |
| Prunus cerasifera. Cherry plum, native to Europe and Asia, naturalized in parts of North America. | Prunus cerasifera. Cherry plum, Hells Canyon, Idaho. |
| Prunus avium. Sweet Cherry, native to Europe and Asia, naturalized in parts of North America. | Prunus avium. Sweet Cherry, near Kettle Falls, Washington. |
| Prunus armeniaca. Apricot. | Prunus armeniaca. Apricot. |
Apple Group: If you encounter a rose family Rosaceae plant with fleshy fruits exhibiting a five-pointed star at the bottom end, it likely belongs to the Apple group within the Almond Subfamily.
Black Chokeberry: Aronia melanocarpa, showcasing the five-pointed star on the fruit, typical of the Apple group.
The rose hip in the Rose subfamily is the only other Rosaceae fruit with a similar five-pointed star. In apple-type flowers, the ovary is inferior, meaning it is positioned below the attachment point of the petals and sepals. This inferior ovary results in the floral remnants persisting at the tip of the developing fruit. The fruit itself is a pome, a type of false fruit. Instead of developing from a swollen ovary, the fleshy part of a pome originates from the enlarged receptacle surrounding the ovary.
Apple group fruits are generally edible, although some, like mountain ash (Sorbus), can be intensely sour and astringent. Cultivated members of the Apple subfamily include apples (Malus), pears (Pyrus), quince (Cydonia), loquat (Eriobotrya), Christmasberry (Photinia), and Pyracantha. The sweetness of many apple-type fruits intensifies after exposure to frost. It’s worth noting that berries from the Heath family (Ericaceae), specifically the Blueberry subfamily, also exhibit a similar five-pointed star from persistent sepals.
| Black Chokeberry: Aronia melanocarpa. | Cydonia oblonga. Quince fruit, cultivated. |
|---|---|
| Malus fusca. Pacific Crabapple. | Malus fusca. Pacific Crabapple. |
| Amelanchier utahensis. Utah Serviceberry. | Amelanchier utahensis. Utah Serviceberry, Canyon de Chelly National Monument, Arizona. |
| Amelanchier alnifolia. Serviceberry. | Amelanchier alnifolia. Serviceberry. |
| Amelanchier alnifolia. Serviceberry. | Crataegus sp. Hawthorn. |
| Pyracantha sp. Pyracantha, an ornamental shrub, Lake Mead, Nevada. | Pyracantha coccinea. Pyracantha, Spokane, Washington. |
| Sorbus scopulina. Mountain Ash. | Sorbus scopulina. Mountain Ash. |
| Sorbus scopulina. Mountain Ash. | Sorbus sitchensis. Sitka Mountain Ash. |
Explore More: Discover additional Rose Family pictures at PlantSystematics.org.
Plant Identification Resources: Identify plants effectively with Botany in a Day and explore edible plants with Foraging the Mountain West.
Return to: Plant Families Index or the Wildflowers & Weeds Home Page.
