All on-site landscaping shall be maintained in good conditions at all times. Landscaped areas must be kept free of litter, and drainage components maintained in working order. In the event of the loss of any on-site landscaping, the owner of the zoning lot shall replace such landscaping by the next appropriate planting season. All landscaped areas must contain a built-in irrigation system or supply hose bibs within 100 feet of all planting islands.