Hello Toedtoes,
Your vision for the space sounds fantastic and your use of tiered beds is an excellent idea to deal with the irregular terrain and make the best of the area you have. I appreciate the thought you've given to the project, and your consideration of plant requirements and aesthetics should result in a beautiful and functional space.
Regarding the proposed depth of your tiers, I think your initial estimate should work quite well. Remember, deeper beds mean more soil and potentially more moisture, which might not be ideal given your wish to have drought-tolerant plants and keep the space low maintenance. However, if you're planning to grow deeper-rooted plants or small shrubs, you might want to consider deeper beds for those.
The layout you're considering - with the tallest tier at the south fence and descending towards the garage - could potentially help with sun exposure. The taller plants at the back wouldn't shade the shorter ones in front as much. Also, your idea of a winding bench that provides a walkway is an attractive one and could make the space more inviting and usable.
As for plant suggestions, here are a few that should thrive in your zone and meet your criteria:
Tall Grasses/Back Tier: Consider varieties like Miscanthus sinensis 'Gracillimus' or 'Morning Light', which are non-invasive, tall, and drought tolerant.
Middle Tier: Salvia greggii (Autumn Sage) could work well for year-round color, as it blooms from spring to fall and is a hummingbird and butterfly favorite. Agastache (Hyssop) is another great option, attracting pollinators and offering an extended bloom season.
Lower Tier: For vegetables, consider compact varieties that are suited for container gardening, like 'Patio Baby' eggplant or 'Tiny Tim' tomatoes. As for perennials, Echinacea purpurea (Purple Coneflower) or Rudbeckia fulgida (Black-eyed Susan) might be nice choices.
Remember to choose plants with similar sun and water needs for each tier to make maintenance easier.
Regarding maintenance, remember to mulch well to preserve moisture and suppress weeds. This can go a long way towards making the garden low-maintenance.
Please don't hesitate to ask if you need further advice, and keep us updated on your progress. I look forward to seeing how your garden develops!
Rubi
