Perennial Gardening: Designing Perennials Gardens

May 5, 2011Gardens, PlantsBy Green Guys

Perennial plants can live many years, so careful planning is required. Determine garden size by available space and the amount of time you have for maintenance. Perennial gardens should be functional, simple to maintain, accessible, and supply a progression of flower colors and textures all season.

When access is available from two sides, a maximum width of 8 feet works well. Use stepping stones to allow easy access through the garden space and to prevent soil compaction.

To begin the design, measure the proposed site. On graph paper, sketch the layout to scale, using a scale of 1 inch = 4 feet or 1 inch = 2 feet, depending on the size of your area. Then proceed with the following steps:

Locate existing structures, walls, fences, walks, etc.
Locate existing plants, such as trees or shrubs. Take into consideration their mature size. These larger plants can be focal points in the Garden.
Sketch the desired outline of the bed. It is often helpful to place a Garden hose around the area to visualize the shape. Measure the line from known reference points to put it on the plan.

Figure 1: Two-sided planting. Each dot = 1 plant.

Figure 2: Island planting. Each dot = 1 plant.

After deciding on the space, follow these basic design principles:

Place plants of the same variety in groups of three, five or seven (odd numbers) to increase the effect of color and texture.
Repeat groups of the same plant type two or three times throughout the space, to give it continuity and create harmony.
Use tall plants at the back of a two-sided garden or in the middle of an island bed.
Complement tall plants by gradually placing shorter plants towards the outer perimeter, ending with low border plants at the edge of the bed. This gives a smooth transition from tall heights down to the border plants. Bring occasional plants forward from their height line to increase variation.
Use various colors, textures and forms to add interest to the garden. Too much variety, however, will over-stimulate the viewer. Consider using more plants of fewer varieties for a simpler, more pleasing effect. However, don’t overuse one type of perennial.
Consider bloom time and foliage (color and texture) to create a succession of interest throughout the seasons.
Complement perennials with annuals and bulbs for bright focal points and accents during low bloom periods.
Leave room for plant growth and allow for individual plant growth habits. In general, plant tall perennials 18 to 36 inches apart, intermediates 12 to 18 inches apart, and dwarfs 6 to 12 inches apart.
Don’t place plants in straight rows — use a scattered or triangular spacing so one mass blends into another.

Two-sided planting
Table 1: Suggested plants for two-sided and island plantings.
Key	Botanical name	Common name	No. plants needed	Size
1	Delphinium hybrid	Delphinium ‘Pacific Giant’	6	#1 pot
2	Paeonia hybrid	Peony (numerous colors)	3	#1 pot
3	Dendranthema x grandiflorum	Shasta daisy	5	#1 pot
4	Aquilegia hybrids	Columbine ‘Songbird’ (blue)	6	#1 pot
5	Leucanthemum hybrids	Hardy fall mum	3	#1 pot
6	Hemerocallis hybrids	Daylily	3	#1 pot
7	Saponaria ocymoides	Rock soapwort	14	2 1/4 in.
8	Oenothera macrocarpa	Ozark sundrop	5	#1 pot
9	Geranium sanguineum	Bloodred cranesbill	6	#1 pot
10	Iberis sempervirens	Candytuft	12	#1 pot
Island planting
1	Heliopsis helianthoides scabra	False sunflower	5	#1 pot
2	Salvia x superba	Salvia ‘Blue Queen’	11	#1 pot
3	Scabiosa caucasica	Pincushion flower (blue)	7	#1 pot
4	Aquilegia hybrids	Columbine ‘Songbird’ (blue)	6	#1 pot
5	Oenothera macrocarpa	Ozark sundrop	10	#1 pot
6	Nepeta x faassenii	Catmint	14	2 1/4 in.
7	Armeria maritima	Sea pink	14	2 1/4 in.
8	Artemisia schmidtiana	Silver mound sage	5	#1 pot
9	Iberis sempervirens	Candytuft	5	#1 pot
10	Hemerocallis hybrids	Daylily	3	#1 pot