The more you know

All plants can, some plants just can't thrive if they are too close together.

This is a good article about garden plants that explains some of the problems certain plants cause others.
http://www.gardeningknowhow.com/edible/vegetables/vgen/incompatible-garden-plants.htm

An explanation of the 'allergy' between cedar and apple, though it's actually a fungus http://nysipm.cornell.edu/factsheets/treefruit/diseases/car/car.asp

Its a fungal growth, I posted a couple links.

Wait.. a fungi??

Yep.

But some how you still want to stare at it.