Selecting Perennials
Light Level Guide
|
Level |
Location |
Amount of sun or shade |
|
Sun |
Open beds, south- or west-facing beds |
No more than 3 hours of shade |
|
Part shade |
East-facing beds |
At least 6 hours of full sun |
|
Shade |
North-facing beds, woodlands |
Essentially no full sun |
Names
Each perennial has a single, specific botanical name that includes a genus, which is capitalized, followed by a species, which is written in lowercase letters. Perennials may have one or several different common names that differ from one region to another. Frequently, the genus is used as a common name, such as delphinium, hosta or iris. When many species within a single genus are being discussed, the abbreviation "spp." follows the genus.
To help you use the tables in this bulletin and order perennial stock, a cross-reference index is included at the back of this bulletin (p. 29) that lists common names followed by botanical names.
Colors
These include currently available flower colors. New culti-vars are released every year that will add to this list. Many seed and nursery catalogs indicate the latest selections available. For plants grown primarily for foliage, the selection and care guide lists foliage color.
Height
The height of perennials varies considerably from species to species, and from one particular environment to the next. Also, many dwarf cul-tivars are available. Plants will often be taller in shade or in rich soil. The guide gives the common range for plants in flower. Foliage height may be much less.
Spread
It is necessary to allow sufficient room for perennials to develop properly. Spread tells you the mature spacing recommended between the center of one plant and the center of the next. For a complete look sooner, plant closer together and remove extra plants before crowding occurs.
Bloom Period
The time and duration of flowering for a given perennial is important to consider when designing a garden. Actual dates of bloom can vary up to 3 weeks from year to year, depending on the weather. Regional climatic conditions, location of the garden and proximity to large lakes can also influence this timing. The dates given are for the central part of the north central region (Detroit, Chicago, Dubuque). These dates will vary by at least 1 month earlier farther south or 1 month later in the northernmost areas of the region. For plants grown for foliage, such as some ornamental grasses, this is the period of significant ornamental value.
Light
Most perennials prefer full sun to light shade. Some tolerate different light levels, and a few require either full sun or deep shade. The guide indicates the optimum light level or range of light levels for each plant. Three light levels are used: sun, part shade and shade.
Hardiness
The number listed in the table indicates the minimum hardiness zone (see hardiness zone map on page 32) recommended for growing a particular plant. It is based on the USDA map of climate zones. Average annual minimum air temperatures for Zone 3 are: -40°F to -30°F; Zone 4: -30°F to -20°F; Zone 5: -20°F to -10°F; Zone 6: -10°F to 0°F.
This system is only an approximate indication because it is based on minimum air temperatures and not on soil temperatures belowground where most perennials overwinter.
Light Level Guide
Hardiness can often be improved by planting in well drained soil and using a winter mulch.
Division/ Propagation
The recommendations given are based on needs for rejuvenating plants and controlling size, not simply propagation. The best time of year to divide a particular plant is given, as well as an average of how frequently it should be divided. A blank in this column indicates that the specific plant does not need to be divided except for propagation. " No" indicates that the plant should not normally be divided.
Special Notes
This category includes miscellaneous care instructions, suggestions for use and special features, as well as undesirable characteristics. Plants that self-seed may be propagated by transplanting seedlings. However, the new plants may not be true to type.
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