Call numbers are the address for the item, where you will find it in the library.
Landscape Horticulture related books can be found in the SB section:
SB1-1110: Plant culture
SB118.48-118.75: Nurseries. Nursery industry
SB169-172.5: Tree crops
SB403-450.87: Flowers and flower culture. Ornamental plants
SB450.9-467.8: Gardens and gardening
SB469-(476.4): Landscape gardening. Landscape architecture
SB599-990.5: Pests and diseases