Creating a chocolate-themed garden in outdoor plant boxes is a delightful way to combine aesthetics with aromatic pleasure. Here are the best plants to include for a lush, cocoa-inspired oasis:

1. Cocoa Plant (Theobroma cacao) – The star of any chocolate garden, this tropical plant thrives in warm, humid conditions. While it requires careful attention in cooler climates, it can flourish in large outdoor plant boxes with partial shade.

2. Chocolate Mint (Mentha × piperita 'Chocolate') – A fragrant herb with dark leaves and a rich chocolatey aroma, perfect for edging plant boxes. It grows vigorously and adds a sensory delight to your garden.

3. Chocolate Cosmos (Cosmos atrosanguineus) – Known for its deep maroon flowers and subtle chocolate scent, this perennial thrives in well-drained soil and full sun, making it ideal for sunny spots in your plant boxes.

4. Chocolate Vine (Akebia quinata) – A fast-growing climber with purple-brown flowers and a sweet cocoa-like fragrance. It’s perfect for vertical gardening in larger outdoor planters.

5. Black Mondo Grass (Ophiopogon planiscapus 'Nigrescens') – While not chocolate-scented, its dark foliage complements the theme beautifully, adding contrast and depth to your plant box arrangements.

For optimal growth, ensure your plant boxes have good drainage and are placed in locations matching each plant’s light requirements. Pairing these plants with mulch or cocoa bean shells can enhance the chocolate garden vibe while retaining soil moisture. Happy gardening!