We all recognize a rose. It looks like this.
Or perhaps these.
When we imagine a rose, we typically envision a flower with a multitude of petals—perhaps a perfect tea rose or a “cabbage” rose. But wild roses, such as this Colorado native (Rosa woodsia, right), only have five. The rest is due to extensive breeding, which has resulted in thousands of named cultivars.
Yet, there are many more members of the rose family (Rosaceae) than just these familiar flowers. In fact, rose family members may be herbaceous (as opposed to woody) plants, shrubs, or even trees. Apples are members. So are stone fruits (peaches, apricots, etc.), raspberries and other brambles, firethorn (Pyracantha), Cotoneaster, and Mountain Ash trees (Sorbus), to name just a few of the more than 5,000 species grouped into 91 genera.
While seemingly diverse, all Rosaceae species share some traits in common. For example, at least in their original form, they all have five petals, supported by five sepals.
In the center of those petals you’ll find a cluster of bright yellow stamens (male) and pistils (female). You may have to part the petals to find them, but they’re there.
Often, rose leaves are compound—comprised of many leaflets attached to a middle stem. Alternately, some rose family species have palmate leaves, such as those in the genus Rubus (raspberries and other bramble fruits). Typically, the edges are somewhat serrated.
While most roses are grown for their stunning flowers, some also feature a fall show of rose hips. If you’ve ever looked closely at a rose hip, you know it closely resembles a tiny apple. Many rose family members also have apple-like fruit.
If you are a gardener, it’s helpful to know which plants are members of this huge family. That’s because they not only share certain traits, but they also share some pests.
During my tenure as a Colorado Master Gardener, I often fielded calls at the county help desk. One of my most memorable conversations started with,
“Hello? I have UFOs in my garden. I think I’m being invaded by aliens!”
The caller went on to describe a strange growth on his junipers. “It’s bright orange and it has tentacles! Is it dangerous? What can I do to make it go away?”
It turned out that this homeowner also had a number of Rosaceae species in his yard, which told me my initial diagnosis was likely correct.
“It’s not an alien. Your juniper has a fungus—Cedar-Apple Rust. It alternates host plants, switching between junipers and other related conifers, and apples and other members of the rose family. It won’t hurt your juniper. If you don’t like it, just wash it off.”
Rosaceae is an important family of plants, valued for both for their fruit and their beauty. The next time you enjoy a bouquet of roses, remember to appreciate all their relatives as well.
Cedar-apple rust photo by PookieFugglestein [CC0]; https://commons.wikimedia.org/wiki/File:Juniper-apple_rust_gall.jpg