Biochar is attracting a lot of attention as it is considered a novel, renewable, and bio-based filler that can be used specifically for developing and manufacturing “bioplastics” for growing plants such as mulch films and plant accessories. The manufacturing of “bioplastics” uses biopolymers but also various additives such as fillers, which are primarily used to replace some of the expensive biopolymers in a biocomposite composition and/or to improve the mechanical properties of the final products. This review aims to demonstrate the applications of biochar as a filler in bioplastics, specifically for horticultural uses; summarize the most recent findings; and discuss future research directions. With this review, we address some of the most important issues related to the requirements for biochar as a filler for bio-based and biodegradable plastics, the effect of biochar properties and loading rates on the properties of biocomposites, and the suitability of biochar for manufacturing of “bioplastics” for horticultural use. We also discuss the advantages as well as challenges and limitations to the use of biochar for manufacturing bio-based and biodegradable plastics for horticultural uses.