It really depends on what the differences between each off shoot could be (I don't know too much about plants, so I'm being quite general). On the one hand, they're all identical in that they're an off-shoot from one specific plant, but other differences could make listing and managing expectations difficult. (Not only that, without a store or being registered as a business, you can't list multiples in the one listing).

So, your official options are actually only one per listing. To list more than one at a time, and not breach the duplicate listing policy (where more than one identical listing is not allowed at a time - that's for Buy It Now listings, you can list multiple auctions, but there's restrictions on that as well, so I wouldn't try any more than a couple at a time http://pages.ebay.com.au/help/policies/search-manipulation.html - scroll down to the end for the auction duplication policy).

I would look at how I could differentiate between them. Perhaps something really basic like small, medium and large off-shoot, or if there's any other key differences that will make each listing unique, then re-list as each one sells for however many you have.

I'm assuming you qualify for 30 free listings per month, so  keep in mind that re-lists etc will use 1 and that once the 30 free are used, it's 50c for a start price up to $19.99, and $1.50 for a start price $20-$99.99