The wild service tree presents an intriguing compatibility with a Southwest positioning. Acknowledged for its robust structure, this tree aligns perfectly with the earth element commonly associated with the Southwest according to Feng Shui principles. The impact is anticipated to be largely positive, creating a harmonious and balanced environment, yet this can vary based upon individual circumstances.

The welsh onion is often perceived as harmonious in the Southwest-facing direction. This outlook subscribes to the timeless Feng Shui principle of 'Earth,' which governs the Southwest. The welsh onion's sturdy, upright growth subtly mirrors the robust, grounding energy of the Earth element, potentially contributing to a sense of stability and balance in the environment. As with all Feng Shui concepts, personal experience is paramount.

The moonflower exhibits a subtle harmonization with the West-facing directionality. It blossoms during the evening, symbolizing the setting sun developing in the West. This creates balanced Yin energies, echoing wisdom and tranquility per Feng Shui principles. However, personal experiences with moonflower may slightly differ, upholding the doctrine of individual vibrational resonance.

The euphorbia contributes subtly to balance when placed in a Southwest-facing direction. This may stem from its inherent earthly energy, which harmonizes well with the Earth element associated with this orientation. As a Feng Shui practice, this does not apply universally and should be reinforced through personal empathy with the plant's vibrancy. The nature of Feng Shui mirrors the concept of uniqueness - what works for one may not work for others.

The mexican creeping zinnia's smaller blooms and spreading habit perfectly harmonize with Feng Shui principles emphasizing balance and modesty. When concerning placement, the South-facing sector will particularly benefit as the mexican creeping zinnia embodies Fire due to its vibrant yellow flowers, a color associated with warmth and inspiration, befitting the South’s corresponding life aspect of fame and reputation. Still, as with all Feng Shui applications, the effect is inherently personal and may diverge depending on individual circumstances.

The blue throatwort is thought by some Feng Shui practitioners to thrive facing North, owing to its affinity with water element which is symbolically associated with North. This though isn't universally accepted. A careful balance must always be maintained; such is the subjective nature of Feng Shui.

The bismarck Palm aligns well with East-facing setups in Feng Shui, believed to be beneficial due to the plant’s robust and majestic nature, which resonates with the Wood element and the Sunrise energy that the East represents. As with any Feng Shui applications, one's individual context and preferences should guide the usage of the bismarck Palm.

The valley oak plant indeed harmonizes well with the Eastern-facing direction in Feng Shui. This is because East symbolizes Wood, which aligns metaphorically with the strong, growing energy of valley oak. It's believed to summon robust health and prosperity. These are broad interpretations and may vary on individual interpretations and distinct settings.