A is for (whoever gets Z starts the next theme)

[twyngwyn]

Grows on a tree

A is for Almond

[twyngwyn]

R is for Rhubarb leaves

[crosbystills]

S is for Strychnine

[twyngwyn]

T is for Thorn apple

[oldie2]

U is for unripe fruit

[twyngwyn]

V is for Veratrum

[electric*mayhem*band]

W is for Wolfsbane.

[crosbystills]

X is for Xenon (only toxic in large quantities)

[twyngwyn]

Y is for Yew

[electric*mayhem*band]

Z is for Zantedeschia.

Next theme: Oz Marine Life. (You people should be OK - it's me that should have trouble). 

A is for Anglerfish.

[crosbystills]

B is for Barramundi