With Botanical Identification level 1 or better, there is a chance that you may find a bulb when you harvest the odd weed. When planted, it will give you one of the basic varieties of Sand Blooms.
Without Botanical Identification, the message on examining the Odd Weed is...
Hmm, there might have been something there, but you just make a mess of it. You need Botanical Identification, preferably level-2, to avoid destroying the delicate weed.