Where to take in Europe an elderly parent who loves flowers and gardens?

Taking my elder parent on a 7 day trip to Spain in mid September. May take a 1–2 day trip to Istanbul and Italy each if can find location worth visiting. Where should she go so she can see nature in a small scale (Nothing off the beaten path- prefers small parks and gardens. Please suggest must see locations for her (no art museums, etc., just garden related locations). Thanks.