If you plan to sell the domain then spend a little time marketing it, say 2-3 months, then make sure you have the Directors/owners names, email addresses, telephone numbers of all the major plant nurseries, online gardening sites, major home improvement retail stores, gardening equipment manufacturers, etc. (it is actually a HUGE niche), in ALL major English speaking countries.
Contact them directly by snail mail and by email. Explain that you own the domain name and are considering developing the domain into an internationally niche killer website and you are looking for potential advertisers or partners for the site and would they be interested in either and who to speak to further about it. (If your aim is to solicit bids to buy the domain then explain you are contacting all the major players in the field - this will let the contact know he could lose out by not trying to purchase/lease the domain from you.
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If you want an evaluation I will give you several.
Undeveloped and just the domain name, sold to a domainer at somewhere like TRAFFIC then a minimum of $500,000 and possibly up to $1,500,000. (May I suggest that you contact Rick Schwartz immediately by the way if this is something you are considering, I am sure he will talk to you about how to handle the sale and get the major publicity possible for it.)
To an end-user the domain undeveloped could achieve between $2,000,000 and $4,000,000, though of course the higher the figure the harder it would be to sell as it would reduce the number of businesses able to afford it. This brings me to leasing or renting the domain out to an end user. I would think that somewhere between $400,000 - $750,000 a year could be achievable in rental income.
Now the biggy!
As a properly developed site, with advertising nationally based around the world, I would imagine that you could be looking at revenue from affiliate sales and advertising in excess of $20,000,000 a year within 2 years. Of course against this would be major costs, the initial site being the largest cost, but you would break even within the first 2 years if done correctly and showing a profit against running cost in your first year.
This is just my opinion, but you have got a gold mine that may if handled correctly also produce platinum.
My advice. Think long and hard what route you want to take before you take it.
Am I jealous? Hell YES. But do I wish you all the best, of course I do.