Creating a black hole complementarity-themed outdoor plant box is a fascinating way to merge cosmic inspiration with gardening. This unique concept draws from the mysterious allure of black holes, emphasizing contrast, depth, and dark aesthetics. Here are the best plants to bring this theme to life:

1. Black Mondo Grass (Ophiopogon planiscapus 'Nigrescens') – Its deep, almost black foliage mimics the darkness of a black hole, creating a striking visual anchor.

2. Dark Opal Basil (Ocimum basilicum 'Dark Opal') – With its purple-black leaves, this herb adds texture and a touch of edible intrigue.

3. Ebony Iris (Iris germanica 'Superstition') – Its velvety, dark blooms evoke the enigmatic beauty of cosmic phenomena.

4. Black Coral Elephant Ear (Colocasia esculenta 'Black Coral') – Large, dramatic leaves with a dark sheen enhance the otherworldly vibe.

5. Midnight Rose Heuchera (Heuchera 'Midnight Rose') – Its dark leaves with pink speckles add a subtle contrast, symbolizing the duality of black hole complementarity.

Pair these plants with silver or white accents like Dusty Miller or Artemisia to represent the event horizon's glow. This theme thrives on balance—dark foliage against lighter elements—mirroring the interplay between light and darkness in black hole theory.

For maintenance, ensure well-draining soil and partial to full sun exposure, depending on the plants chosen. Water consistently but avoid over-saturation, as many dark-themed plants prefer slightly drier conditions.

A black hole complementarity-themed plant box isn’t just a garden—it’s a conversation starter, blending science, art, and nature into one captivating space.