Rosaceae Fruit
Rosaceae Fruit
Whilst recently researching the wildflower families, I fell down a fruit-shaped rabbit hole. And it is because of the amount of variety shown in the fruit of the Rosaceae, or rose family.
Japanese rose Rosa rugosa
For more on what makes a plant a member of the Rosaceae, check out my recent blog Wildflower families: Rosaceae.
Where to start? There’s a lot of variety, and taking a look at my Fruit variety and terminology blog might help.
Rosaceae Fruit: Aggregate Fruit
Rosaceae fruit are one to two seeded, and often form together into aggregates, or aggregate fruit. Think of a blackberry or a raspberry. Each of those little lumps (or drupelets) houses a seed. They clump together to form what we see as one fruit, although it is an aggregate of many. Think how many seeds you find when eating one blackberry!
Jersey Post copyright 2027 Jersey bramble Rubus caesarius
If you have time to spare, have a look at my step by step blog on painting a blackberry.
Rosaceae Fruits: Drupes
Some other Rosaceae grow drupes. A drupe is a fleshy fruit which has a thin skin and grows around a central hard stone. Inside the stone (or pip, or kernel) is the seed.
Plum Prunus prunus fruit
Plums and cherries are drupes. In the states, the term “stone fruit” is used. This refers to any soft fruit with a woody stone, such as apricots and peaches.
Peach Prunus persica with stone (and seed) removed
Rosaceae fruits: Aggregates of Achenes
Some have aggregates of single-seeded achenes. Some of these have spines which catch onto fur for seed dispersal. These are actually called awns, and are formed from the persistent remains of the style.
Piri Piri bur Acaena novae-zelandiae seedhead and individual achene with awns
Other examples include Herb bennet, Geum, and Mountain avens.
Water avens Geum rivale showing flower and seed head with awned achenes
Others, like Meadowsweet, twist their achenes together into a spiral.
Potentilla seed heads look a lot like those of the Ranunculaceae family, an assembly of achenes borne in a globe-like arrangement.
Rosaceae Fruit: The Pseudo-fruit (Rosehip)
Rosehips are not made from the carpels of a flower. The seeds within are formed from carpels, with their thin coats. But the red or orange fleshy part of a rosehip is called a hypanthium. It is just a fleshy shell, housing the real fruit, the achenes (formed from carpels), each bearing one seed. The hypanthium is formed from swollen receptacle flesh.
Japanese Rose Rosa rugosa rosehip cross section
The receptacle is the part of the plant where the flowering parts are attached, not the female flower parts themselves. Receptacles lie below the flowering structure, and explains why we see that distinctive brown bit at the “bottom” of a rosehip. They are the remnants of the calyx and other flowering structures, and if you look closely you can sometimes see old stamens. Which makes that the “top” of the pseudo fruit, I suppose.
Rosaceae Fruit: The Pome
One of the most commercially important Rosaceae, the apple, carries its’ seeds in a Pome. A pome is a swelling of the receptacle, not the carpel. It is built of several hypanthium (enlarged receptacle) which have grown together.
At the centre of this we find the pericarp which contains five to thirteen seeds (it’s commonly known as the apple core), depending on how successful pollination was.
Diagram showing the structure of the Pome (apple)
So next time you eat an apple or a pear, remember that the distinctive brown bit at the “bottom” is the residual flowering parts, specifically the calyx.
Pear sprig with blossom and fruit Pyrus communis
For more on pomes, check out this blog from Where the spruce eats. To be sure you can tell your pome from your drupe, take a look at this blog from Toronto botanical garden.
Rosaceae Fruit: The Strawberry
The strawberry bears its’ seeds on the outside, and in fact every yellow seed is a strawberry fruit. The fleshy part (which we eat so cheerily) is made from swollen receptacle tissue, rather like the apple (a pome).
Wild strawberry Fragaria vesca with external fruits and seeds on a swollen receptacle
However, the big difference is that the seeds of the strawberry are on the outside not the inside, and it is the only fruit which does this. It is therefore not only delicious but also remarkable.
Conclusion
This blog is far from exhaustive, and I have no doubt I could find enough to write an entire blog about the core of an apple. I hope this serves as an introduction to the variety and fascinating structures of the fruit of the Rosaceae.
Sketchbook study of the Dog rose Rosa canina
