http://visual.merriam-webster.com/

Its by Merriam Webster and it is a visual dictionary. You can find the names of all kinds things, even little technical things you, as a native speaker, may not know.

Seriously, explore the site a bit and see what I mean. It's free.

I must admit peduncle, epicalyx, and achene are all new words to me

I guess I'm a little old school...

I've been using www.dictionary.com for about 10 years. Should I update my dictionary website selection?