Garden plants or trees — plants that are planted in a garden (often decorative trees/shrubs).
庭の植木を冬に剪定した。
I pruned the garden plants in winter.
裏庭の植木が去年よりずっと大きくなった。
The garden plants in the backyard have grown much bigger than last year.
公園の植木が春に花を咲かせた。
The park's planted trees/flowers bloomed in spring.
Potted plants — small plants grown in pots or displayed in stores; can refer to indoor ornamental plants.
部屋の植木に毎朝水をやっている。
I water the potted plants in my room every morning.
店先の小さな植木が道行く人の目を引いていた。
The small potted plants at the shop front were attracting passersby.