I’ve lots of thoughts. My 2 cents compounded:
If you’re not there on assignment and being paid, you’re not a professional. If you’re there to get wedding shots, portraits, etc., and are using their grounds, why shouldn’t they be compensated? You don’t get space in a portrait studio for free–why should they be required to give it all away?
If you’re using the space often, build it into your fees (at whatever level breaks you even), and take the street cred of an ID card (which if you proudly display might get you some ‘street’ traffic while there on assignment or not by other visitors), and bonus: A free lanyard! That alone is worth $3 at most places.
If you don’t use it often, you can rent by the hour. And siting the location seems fair–you’d not want your art displayed without proper accreditation, and their garden sounds like it’s designed with the art of landscape in mind.
The astro shots I’ve been taking are from Tonto National Forest, at Bartlett Lake. They charge $6 a day, and I gladly pay it (I bought ahead, 5 lottery-style cards available at most every local merchant; when you arrive you scratch off the date/month/year, good for 24 hours and valid ahead of time to 2013. It’s $96 for a yearly, so had I bought one in January before I’d been there 4 times, by the end of the year I’d be paying $5.25; in the long run, I save. As it is, I’d break even. If it’s worth shooting as a background, it’s worth paying for. And that only makes it more exclusive to offer portraiture from.
