The horse chestnut tree derives its nutrients and energy from photosynthesis.  For more on this process see Nutrition.  Therefore, it is very important that the efficiency and amount of photosynthesis being done is maximized.  All throughout the plant kingdom we see adaptations to increase the surface area of photosynthetic areas of the plants.  In Aesculus hippocastanum, this increased surface area is seen in the unique and aesthetic leaves.  The leaves are palmately compound, meaning that they have multiple leaflets coming from one single point at the point of the petiole.  Horse chestnut leaves usually contain about 7 leaflets which usually display more chlorophyll on the side facing upwards than on the bottom side.  This is due to the greater quantity of light received by the top surface.  The leaflets are usually 10 to 20 cm (approx. 4-8 in) long.  This provides more than adequate surface area on which light can be received to undergo photosynthesis.
The fruits of the horse chestnut are disputably the most interesting features of the tree, though not completely unique to this species.  They are highly adapted to provide support and protection for the encased embryo.  One characteristic of the seed that contributes to this protection is the spines that coat the outside of the seed.  Secondly, not only are the seed coverings very hard, the seeds themselves are very resistant.  In fact, there is an entire sport based off trying to break these seeds.  For more on these games see Interactions. Another level of protection these fruits provide for the enclosed embryos is the toxin it contains to avoid predation.  For more on this toxin see Health & Horse Chestnuts.

Secondary growth is the phenomenon in which plants increase in girth, not height.  This process begins with the procambium growing together to make a concentric path around the length of the trunk.  This new layer is called the vascular cambium and ultimately excretes the secondary xylem towards the pith of the tree and the secondary phloem towards the bark.  As time progresses the xylem takes up a continuously larger amount of area and forces the vascular cambium to continuously get grow outwards. Therefore, if you could observe the layers of the trunk of the horse chestnut tree from the outside to the center you would first see the bark including the secondary phloem, the vascular cambium, the secondary xylem, and then the pith of the tree.  This ability is shared among dicots and gymnosperms.  Plants with secondary growth are allowed much more support and protection than those with only primary growth. 

In general, flowers are in angiosperms and function as reproductive organs.  The horse chestnut blooms in spring with large white flowers with yellow and/or red spots.  The flowers are arranged into a "spike" measuring to about 5 to 13 cm (approx. 2-5 in) wide and 13 to 30 cm (approx. 5-12 in) high. Each individual flower consists of 5 petals.  These flowers usually appear in May and final development and ripening of the seeds begins in late August or early September.  This adaptation not only supplies us with an aesthetic tree, but attract pollinators and are the sites of eventual fertilization of the egg by the sperm.   If you think these flowers are pretty, take a look at the flowers on Kiwifruit!

Go Home.                                            Go to top of page.                                          Learn about nutrition.