Tomatoes are the most important glasshouse crop, taking up over 8 million sq. ft. of the total glasshouse area of 8.9 million sq. ft. (Department of Agriculture estimate). Other main glasshouse crops include cucumbers (0.46 million sq. ft.), French beans (0.083 million sq. ft.), grapes (0.405 million sq. ft.), and lettuce. Auckland has the largest area of glasshouses (2,834,800 sq. ft.), followed by Christchurch (1,152,838 sq. ft.) and Nelson (1,387,000 sq. ft.). There are commercial glasshouses in most districts of New Zealand. About 40 per cent of glasshouses are heated.
Glasshouse production units are small by English and European standards, the average being four to six glasshouses. Single-span 30 ft × 100 ft glasshouses are preferred, heated mainly by hot water, though hot air heating is coming into favour in some districts. Trickle irrigation is popular because it saves time in watering and feeding and helps to control plant growth and development more closely. The soil is usually sterilised each year by steam or special chemicals. Some southern growers who have difficulty in using chemical soil sterilants because of low soil temperatures resoil their glasshouses annually. Paint-spray equipment is used extensively to apply therapeutants.