Wednesday, September 21, 2011

Types of tree fruit

Ginkgo (Ginkgo biloba) "fruit" is a naked seed covered by sarcotesta (aka Cycad seed coat)
Lately we have been noticing tree fruits: Ginkgo, London planetree, crabapple, and dogwood are among the ones we have photographed.  In addition to trees, we are enjoying sightings of rose hips and juniper berries.

Image: Dogwood (Cornus) fruit (a drupe)
The juniper berry is not a berry but rather is a fleshy cone of "merged scales".  Despite its fleshy appearance, the juniper's berry has a naked seed typical of gymnosperms.  Peter Thomas in Trees: Their Natural History defines the naked seed of the conifer as follows: "The scales of conifer cones can be bent apart to reveal the seeds without physically breaking anything apart".  This is not the case for angiosperms (also referred to as hardwoods by Thomas) where "the seed is completely enclosed by the fruit and cannot be seen without breaking into the fruit, whether it is dry nut or a fleshy plum" (Thomas).

Image: London planetree (Platanus acerifolia) seed ball (a capsule)
Thomas groups hardwood tree fruit into four categories: (1) dehiscent dry fruit; (2) indehiscent dry fruit; (3) succulent fruit; and (4) false fruits.  It should be noted that not all fruit are fleshy and some fruit have been falsely classified as seeds in doing so (H. D. Harrington in How to Identify Plants).  Dehiscent fruit "opens naturally to release the enclosed seed or seeds" while indehiscent fruit "does not open to release the seed or seeds" (Harrington).  Some examples of dehiscent fruit are Acacia (legume); magnolia (follicle); and horse chestnut (capsule).  Example of inhediscent fruit include cashew (acene); oak, beech (nut); maple, ash, linden (samara).


Within the succulent fruit category are three major sub-classes: simple, aggregate, and multiple.  Berries (ex: blackcurrant, banana, date), drupes (ex: plum, cherry; walnuts, almonds), hesperidium (ex: orange), pepos (ex: watermelon), and pomes (ex: apple) are simple succulent fruit; raspberries, blackberries, and rose hips are examples of aggregate succulent fruit; and mulberry is an example of a multiple succulent fruit (Harrington; Thomas; botanical-online.com)


Harrington classifies the apple, rose hip, and fig as false fruits because these fruits are "supplemented with other structures".  Stamens and petals grow "up and around the true fruit" of the apple (a pome), the rose hip (an achene), and the fig (contains a drupe).

What tree fruits are you seeing?

8 comments:

  1. My favorite of the moment is Callicarpa americana.

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  2. It's pawpaw season!!! When I moved in February, I moved away from all the places I had found pawpaws. So this weekend I want to hit up some parks and see if I find some new hiding spots of the trees.

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  3. I like juniper berries, because they make gin!

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  4. I'm looking after our neighbours' garden while they are on holiday, and this includes a wonderful fig tree which has just burst with ripe figs during their absence.. I have been fascinated by their sheer beauty but also their strangeness as I was unaware until I looked them up that they are not fruit so much as a kind of inside out flower? Thank you for this excellent post about the different types of fruit, very informative.

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  5. Great! thanks for letting me know about the post...

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  6. I am trying to identify a fruiting tree found in the yard of my new home. It has a simple serrated leaf medium sized, paper bark that is loose, a one inch bumpy berry type fruit that is pale green then ripens to light red pink juicy. Amyone recognise this fruit tree?

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  7. local ecologistSeptember 02, 2012

    Anonymous: please submit a photo here (you can include a link in a comment) or email it to info @ localecology.org.

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