The common vervain plant is deemed suitable for North-facing areas, according to Feng Shui principles. This is majorly attributed to its 'water' energy that aligns seamlessly with the symbol of 'water' often tied to the Northern direction in Feng Shui. However, planetary forces can be unique in each scenario, leading to different degrees of compatibility based on personal context.

In Feng Shui, the barley aligns with tranquility, nourishment, and resilience. It could bestow an energy of calm stability when situated in the Northeast direction. This placement has been associated with the earth element, reflecting the barley's inherent link to soil and sustenance. As always, individual results may vary, and the effect is subject to the unique interaction of energies in your environment. Therefore, it's recommended to consult a Feng Shui professional for personalized advice.

The pigeon pea harmonizes well with the Southwest-facing direction. This is due to its robust and woody nature, which relates symbolically to the Earth element that governs the Southwest according to Feng Shui principles. However, each individual's energy may result in unique interactions.

The threadleaf bluestar may harmoniously align with Feng Shui practices when placed in a North-facing position. Its blue hues echo an element of Water, commonly associated with the North. Please note that Feng Shui interpretations vary and this suggestion is merely one perspective.

The pickerelweed plant is regarded as flexible in Feng Shui, harmonizing with North-facing settings. The inherent adaptability of the plant symbolizes resilience and mirrors the constant flow of the northern Water Element. However, each individual still needs to interpret this in light of their unique energies and settings.

The mountain witch alder aligns particularly well with Northwest-facing homes. This plant embodies strong, grounding energy, resonating with the earth element influential in this direction. Keep in mind, Feng Shui compatibility varies greatly and this advice should be adapted to individual circumstances.

The italian bugloss, with its vibrant colors, is classically compatible in east-facing areas. The reason being, in Feng Shui, the east symbolizes health and balance, colours of italian bugloss signifies renewal and life, hence amplifying the region's Chi. However, each setting invokes a unique energy pattern, calling for personal contemplation and judgment.

The false-gold-flower rhododendron is deemed harmonious in Feng Shui practice, largely due to its lustrous gold-like flowers symbolizing wealth and prosperity. Its compatibility with the south-facing direction is appreciable as this is linked to the element of fire in Feng Shui, aligning with the plant's vivacious energy and vibrant bloom. However, interpretations can vary based on personal aura and environment.