Your options are to appeal the appraisal, make it agricultural (community garden or farm crops), raise bees or anythng like that to get the taxes down.

in the SF peninsula and down to Cupertino there was a builder who built about 30k homes in the 50s and 60s  called Eickler these were modern heat in the floor tons of glass interior walk ways with gardens in them etc etc.. very unique ..

Or a garden shed, art studio, etc...Just a thought... 

We're able to afford the place as a 2 flat, but still pondering legal options for monetizing the garden unit, if any exist. 

Upkeep and maintenance, landscaping, garden and fencing in the backyard.

So it's a long road before you have any income coming in from that garden and there is absolutely no guarantee it will ever even get upzoned. 

-They handle all aspects of property management, allowing you to enjoy a steady income with no stress.Some Top Areas to Invest in Orlando:-Winter Park-Windermere-Winter Garden-East Orlando-OviedoEach of these areas offers a blend of amenities, a desirable neighborhood atmosphere, and property appreciation potential, making them prime locations for passive income investments.

This is why a machine cannot calculate for the irrationality of a person buying a house over value because they like the cute garden. 

A good use for scrap counters/stone is breaking them up with a sledge and using them for garden stepping stones, borders & "mosaics".

I'm particularly passionate about Multifamily Units and New Builds.Outside of real estate, I enjoy exercising and gardening!!