Discovering Botanical Families: Rosaceae

Our first foray into the world of botanical families begins today with the no less famous Rosaceae family.

If they’re synonymous with nobility, refined fragrance and the promise of fruit, plants belonging to the Rosaceae family are also responsible for an appreciable horticultural heritage. The eponymous genus Rosa (roses) alone makes this family one of the best known. But other genera have also been added to the family portrait.

The Rosaceae family includes over 3,000 plant species in nearly 100 genera. The floral and vegetative diversity of this family, which includes trees, shrubs and herbaceous plants, as well as its particularly wide geographic distribution in the boreal hemisphere, makes it a favorite among gardeners. You can even bet that several Rosaceae are already part of your landscape.

Let’s take a closer look at the characteristics of this family. Remember that more than one criterion is needed to determine whether a plant belongs to a botanical family. For example, Rosaceae generally have 5-petalled flowers, although not all 5-petalled flowers are Rosaceae.

The Flowers

Rosaceae flowers are hermaphroditic or bisexual, meaning they all have male organs (stamens) and female organs (pistils). They are actinomorphic, meaning that the flower form can be divided along several axes. The flowers also have five petals and a very large number of stamens. It is this last observable characteristic that is particularly unique to plants in the Rosaceae family. Note that although the majority of Rosaceae flowers have five petals, it’s not uncommon to find specimens with more petals – just think of roses. It’s the transformation of the numerous stamens that leads to the birth of more petals. But that’s another story!

Examples Of Flowers

Here are four well-known species of the Rosaceae family. All have five-petaled flowers and several stamens.

And Van Houtte’s Spirea, A Rosacea?

Well, yes! Spiraea x vanhouttei‘s inflorescences are made up of many small flowers, but it also has all the necessary characteristics to be included in this family. Take a good look at each flower.

The Leaves

They are always alternate, exceptionally opposite, and have a blade with a toothed to lobed margin. They may be whole or compound. Stipules are frequently present, sometimes highly visible, but sometimes very small or even absent. Stipules are small structures usually resembling tiny leaves at the very base of the leaf. Here’s an illustration to help you understand.

Fruits: Plenty To Choose From!

This is where things get a little complicated, as there are several types of fruit in this family. In botany, there are several ways of characterizing fruit (fruit being the result of the transformation of the ovary of a flower that has been well pollinated). The literature will tell you that Rosaceae fruits are mainly drupes, piridions, achenes, follicles and even rose hips. That’s a lot of people at the terminology banquet. But let’s take a closer look.

A: Apple and pear trees produce “false fruits” called piridions;

B: Cherry, plum and peach trees produce drupes;

C: Strawberry plants produce achenes (the small seeds that cover the strawberry);

D: Raspberry and mulberry trees make agglomerations of small drupes, drupeoles;

E: Roses make rose hips;

F: Ninebarks make follicles.

It would probably take several articles to describe each of these fruit types, but for now, just know that plants with fruits resembling those named above have a good chance of belonging to this family.

Are you starting to think about the Rosaceae you know? You’ve probably already come across a few. Here’s a list:

Fruit Trees

• Apple tree (Malus domestica)
• Pear tree (Pyrus communis)
• Cherry (Prunus sp.)
• Plum (Prunus domestica)
• Apricot (Prunus armeniaca)
• Peach (Prunus persica)
• Almond tree (Prunus dulcis)

Fruit Bushes

• Raspberry bush (Rubus idaeus)
• Blackberry (Rubus fruticosus)
• Serviceberry (Amelanchier sp.)
• Black chokeberry (Aronia melanocarpa)

Ornamental Trees And Shrubs

• Rowan (Sorbus aucuparia)
• Hawthorn (Crataegus sp.)
• Shrubby cinquefoil (Dasiphora fruticosa)
• Rose (Rosa sp.)
• Cotoneaster (Cotoneaster sp.)
• Ninebark (Physocarpus sp.) 
• Meadowsweets (Spiraea sp.)

Herbaceous Plants

• Lady’s mantles (Alchemilla sp.)
• Goatsbeard (Aruncus dioïcus)
• Queen of the prairie (Filipendula rubra)
• Canadian Burnet (Sanguisorba canadensis)
• Strawberry (Fragaria sp.)

In A Nutshell

To identify whether a plant belongs to the Rosaceae family, you’ll need to observe the presence of more than one of the following criteria:

• 5 petals;
• Several stamens (more than 10);
• Leaves with toothed margins;
• Leaves with stipules at base;
• Several types of fruit.

Roses are the undisputed star of this family, but you now know that other genera are also included, notably our fruit trees. We hope that this short tour of the Rosaceae universe will help you to identify the species that make up the family more easily, and don’t forget to keep your botanical vigilance: the observation of more than one physiological criterion is necessary to classify with certainty the belonging of a plant to a botanical family. Enjoy your observations!

In our next instalment… Asteraceae.