This site is operated by Botana. Contact: hello@botana.app. There is no account.
The plants you pick stay in the page address. They are not saved on a server. If you choose a language, that choice is stored on this device so the next visit can open it.
If you install Botana, a copy of the app is saved on this device so it can open offline. That happens only after you choose Install.
Advertising cookies are used only if you allow them. Google may then store cookies to show and measure ads. The legal basis is your consent. You can refuse, and you can withdraw consent at any time with Cookies. Refusing ads does not change the planting guide.
You can ask what data is held about you, and you can complain to your data protection authority.