Tickets cannot be purchased for "Grand Harlingen Garden" as it does not exist as a public attraction.
Since "Grand Harlingen Garden" is not a recognized public attraction in Harlingen, there are no tickets to be purchased, either on-site or online. For actual attractions, the availability of on-site ticket purchases varies.
Many popular tourist sites now encourage or require online ticket purchases in advance to manage crowd levels and reduce waiting times. Some smaller or less busy attractions may still offer ticket sales exclusively at the entrance. It is always best practice to check the official website of any real attraction for their current ticketing policies and options to avoid disappointment upon arrival.