When my husband and I moved into our St. Louis suburban home in 2001 we inherited a south-facing, 18-foot tall, very steep, lawn-covered hill. I looked at that hill and saw it as a great opportunity. The grade itself provides privacy from neighbors, and the hill faces the house so I knew that we would get the full visual benefit of turning it into a garden. My husband looked at it and wasn’t convinced!
Before even beginning my landscape planning, I knew I needed to get a jump-start on screening the surrounding houses, so right away I planted several ‘Keteleeri’ upright juniper on the top eastern corner of the hill. These large evergreen shrubs would eventually satisfy my need for a 12-foot screen, without overgrowing the space.
In order to create the formal look I desired for the rest of the yard, and to define the lower edge of the hill, we had a 4’ tall concrete block retaining wall installed. By cutting into the hill, the wall also helped to expand the flat, useable area of my yard. I resisted multiple terraces, because I wanted the area above the wall to be dominated by plants, not hardscape.
I kept my choice of plants to those with very fine foliage, small flowers, and a mature height of less than 3 feet tall. This makes the plants appear farther away and the property appear larger. I also wanted to create the feeling of an alpine meadow, which requires adhering to a specialized color scheme of mostly bluish purple, true pink, and red, with just a dab of clear yellow. Most importantly, the plants had to be drought and sun tolerant. To that end, I used a mixture of native and adapted plants.
I implemented the first round of planting over 2 years, starting with small wholesale liner plugs (72 plants to a flat). Additionally, I fill in every year with new plants to replace what has not done well, or just for the fun of trying something new.
Each year, in the very early spring, my husband and I cut back all the plants on the hill. We don’t remove any of the dead and dried plant material, we simply shred it and leave it to decompose between the plants and return the nutrients to the soil. In mid spring, before the plants fill out, we hand weed quite a bit. Mainly we tackle the woody trees sprouting up. We battle honeysuckle, maples and red bud trying to turn my prairie like hill garden back into a woodland forest! The more we pull during the early spring, the less we have to do the rest of the year in terms of maintenance. But by the time the plants fill out in late spring, if we have done a good job of weeding to that point, there is little weed competition for the rest of the year. I fertilize with an organic slow release fertilizer annually, and water about once a week.
The three main initial grass varieties on the hill were the backbone of the design: Pennisetum orentale ‘Karley Rose’, Panicum virgatum ‘Shenandoah’ , and to a lesser extent the Miscanthus sinensis ‘purpurascens’ (which is a beautiful grass, but hasn’t thrived for me).
The perennials successes are led by the Nepeta (Catmint), Salvia greggii ‘maraschino’ (which surprisingly has come back for me for years despite it being only rated hardy to zone 7) and Amsonia hubrechtii, which has a fantastic golden fall color. Pink Missouri primrose, several types of lavender and Plains Coreopsis (a self seeding native annual) also have established well.
Another species that is thriving is Rhus Glabra, the only woody species on the hill. It is a native suckering shrub that I planted in the opposite corner from the evergreens to visually balance their height. It has an outstanding fall color and is doing very well (maybe too well as it also wants to take over now…but it is pretty, and native, and for the most part the sumac and I are friends).
I’ve also had a few disappointments – the Gaura ‘siskiyou pink’ and the Agastache rupestris I tried, both bloomed beautifully the first year and looked fantastic by my design criteria, but died out after only a year. I’ve had little luck with Russian sage surprisingly, and also have been disappointed by several types of Penstemon, although last year I planted more Penstemon, so we’ll see if I fare better this summer.
I considered the Hill portion of the hill garden mature when it was 3 years old…about 2007. The surrounding woody plants, the smooth sumac, the junipers, and many of the trees and shrubs in the rest of the yard have been growing now for over a decade, and although the hill itself still looks a lot like it did in 2007, the perimeter of the yard has gotten much larger and the yard is very private now.
Our planning and work has paid off, as you can see in the photos. Instead of a bland, hard-to-mow steep slope of turf grass, we have an ever-changing view of diverse and colorful plants to enjoy throughout the year. We’ve provided a nice sized area for local bird and pollinator insect populations, and a pleasant backdrop to the various activities in and around our suburban home. Most of the winter we have a resident fox who likes to sleep in the hillside sun…and, for a plant lover like me, I’ve created a wonderful place to test and enjoy a variety of grasses and wildflowers in my own backyard paradise.
The hill changes with every season. Here are a few more of my favorite photos of the hill garden, enjoy!
Mary Francois Deweese is a Registered Landscape Architect and Owner of Acorn Landscapes in St. Louis.