Yes, when the applicable award requires it. For casual horticulture work, overtime is not paid just because a shift goes past a generic ordinary day, and weekend work is not automatically a penalty rate.
Under the Horticulture Award, ordinary hours for a casual can fall on any day of the week between 5:00am and 8:30pm. Overtime generally applies if you work more than 12 hours in an engagement, more than 12 hours in a day, or more than 304 ordinary hours in an 8-week period. Public holidays and some other situations have separate rates.
We pay according to the award classification and the terms of each engagement. Check Fair Work’s Pay and Conditions Tool for the current figures for your classification.