The common Hoptree harmonizes favorably when placed in the Southeast direction. This is based on Feng Shui principles that believe tree and wood elements support wealth and prosperity, commonly associated with the Southeast. However, experiences may vary, thus personal interpretation is advised.

The adlay plant is deemed harmonious with the Northeast direction in Feng Shui culture. This stems from the plant's earthy, grounding energy, which resonates with the Earth element dominant in that direction. However, interpretations can vary, respecting the fluid nature of Feng Shui perspectives.

The steeplebush plant tends to flourish under well-lit conditions, aligning it harmoniously with north-facing arrangements, as this direction promotes clarity and insight according to Feng Shui principles. However, the strength of this compatibility may be subjective, shifting under differing perspectives.

The mexican Lobelia holds a fascinating aura with neutral Feng Shui energy, which makes it a palatable addition to various spaces. Working harmoniously with a North-facing direction, it snugly fits into Water element's domain, symbolizing career growth and wisdom. Its warm thriving nature subtly echoes the Feng Shui principle of fluidity and movement. Please note that the balance it brings can vary, reflecting the intricate subjectivity of Feng Shui.

The rough maidenhair fern plant embodies a steady growth and distinct tranquility, which complements the energy of the East direction. As per Feng Shui principles, the East represents dawn and renewal - a harmony that rough maidenhair fern resonates with, potentially influencing a positive flow of Qi in your space.

The engelmann daisy boasts a strong affinity to the South, likely due to its vibrant yellow blooms that symbolize 'fire' in Feng Shui, much like the Southern direction. This plant can encourage positive energy when placed in South-facing positions. However, perception and results might vary, reflecting the uniqueness of every individual's chi.

The rose cactus is generally seen as auspicious in Feng Shui due to its vibrant blooms symbolizing vitality and energy. This plant is notably compatible with the Southwest-facing direction, which represents relationships, love, and the feminine aspect in Feng Shui. Rose cactus's radiant energy can harmonize with this space, enhancing interpersonal dynamics and sparks of romance. However, its compatibility should also be evaluated based on personalized Feng Shui elements for finer adjustment.

The proso millet is an intriguing choice for Feng Shui applications. Its propensity for robust growth symbolizes determination and perseverance. Situated in the Northwest direction, it could foster the energies of helpful people and travel, as in Feng Shui, Northwest is connected to these aspects. Always remember, each placement resonates differently to individual users, diligence in personal observation is advised.