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Tree Flowers (and fruits) 


Everybody loves sweetgum trees because of the fun time they have raking up the spiny clusters of fruits from lawns, sidewalks, etc. Liquidambar styraciflua (family Altingiaceae, although older works, including many still in use, place sweetgum in the Hamamelidaceae) is native to Ohio, but just barely, as it is primarily a southeastern swamp tree seen here mostly along streets and on lawns. There's one in the Clintonville neighborhood of Columbus that seems to produce delightfully larger-than-average gumballs, shown here flowering in April, 2006.

Like many trees, sweetgum is monoecious, producing unisexual flowers different parts of the same tree.


Sweetgum flowering, April 26, 2006, Columbus, OH.
Sweetgum's staminate flowers are produced in spherical heads presented in upright elongate clusters of about a dozen heads each. The pistilate flowers are also in heads, but the heads are solitary. The use of the word "heads" is used here as a colloquial synonym for "capitulum." A capitulum is a kind of infloresence in which many usually small flowers are all attached at the same point on the flowering stem (the peduncle), and the individual flowers are stalkless (sessile).  
sweetgum flowering

Sweetgum flowering, April 26, 2006, Columbus, OH. Staminate capitula are numerous and pressented upright, whereas the pistillate capitula are solitary and dangling. 
sweetgum pistilate capitulumsweetgum stamens on sidewalk

Sweetgum flowers. Left: pistillate capitulum, April 26, 2006. The elongate and eleborate stigmas are all that are evident. Right: Staminate flower clusters on the ground just a few days after flowering (May 1, 2006.) 

sweetgum flowers talkikng

Sweetgum pistillate flower head and a persistent fruiut from last year, April 26, 2006, Columbus, OH.

These big spiny things of which there are five shown below are not the fruits per se, but are multiples of many small fruits. Each 2-parted sub-unit, of which there seem to be about 60 per gumball, is a dry fruit all on its own, which originally was the ovary of a tiny individual flower. (A fruit is a ripened ovary containing seeds.) Since they stay together at maturity the gumball is an example of a multiple fruit. More precisely, it is a multiple of capsules, as the little units are in fact capsules, i.e., dry fruits that split open along more than one seam to release seeds.   

sweetgum fruits

Sweetgum multiple fruits, November 27, 2007.