The rattlesnake plant has a unique, intriguing aura. It is closely associated with preserving tranquility and expanding imaginative thinking. It is commonly believed to be compatible with an East-facing direction. This is because East signifies growth and revitalization, similar to the lively presence of the rattlesnake plant that symbolizes constant evolution and renewal.

The common bird's-foot trefoil is generally thought to convey a balance of Yin and Yang energies. It might be especially harmonious when oriented to the North, a direction linked to water's fluidity, in concert with the common bird's-foot trefoil's adaptive nature. As in Feng Shui interpretations, this compatibility might vary on a case-by-case basis.

The scarlet sage harmonizes well with a south-facing setting, one of the resonances being its vibrant red hues that align with the Fire element, typically associated with the South in Feng Shui. This connection may boost positive energy flow or 'chi'. However, Feng Shui interpretations vary significantly, hence the effect might differ.

Traditionally, the sweet pea is seen as a harmonious entity in Feng Shui. Its positive attributes including inducing calmness, enhancing emotional well-being, and promoting restoration align well with the South-facing direction, converging the energies with the notion of ‘Li’, representing fame and reputation in the Feng Shui BaGua. Nonetheless, personal experiences with Feng Shui may vary, and the guidance here serves only as a broad reference.

The calla lily is suggested to have a gentle congruity with the North-facing direction. The reasons are largely related to the symbolism of water inherent to that direction in Feng Shui. The calla lily, with its soothing colors and water-like spots, can act as a subtle enhancer of such properties, further softening and harmonizing the energy flow.

The spiny sowthistle holds moderate harmony when situated in the Eastern part of the house. This is attributed to the resilient nature of the plant that resonates with the wood element, typically associated with East. However, individual experiences may diverge based on other variables often involved in Feng Shui practices, such as the plant's health and the overall energy flow in the house.

In Feng Shui, the bull thistle is seen as a powerful force of resilience and growth. Its prickly nature might suggest a repelling of negative energies. Facing North, it might tap into the elemental energy of water, enhancing its spiritual resilience. However, its interpretation can vary greatly.

The red box exhibits moderate Feng Shui compatibility. Its vibrant energy aids in releasing stagnant chi, enhancing vitality. For the North direction, it can subtly enhance water element owing to its rustling leaves symbolizing the sound of water - a fundamental force in directing energy flow. However, personal experiences might vary due to the intricate nature of Feng Shui.