The key to successful planning for almost all flower bulbs is site selection. The major factors that must be considered are:
The key to successful planning for almost all flower bulbs is site selection.
The major factors that must be considered are:
The soil at the site must be well drained! This is a critical factor for planting flower bulbs. The easiest method to determine if the site drains well is to observe the proposed planting area the day after an intensive rainfall. If water remains in the site, then the soil does not drain adequately. Therefore, either another site needs to be selected or the drainage needs to be improved.
Check soil pH of the site! Once drainage in the site has been assessed, test the soil for the pH level. It should be within a range of 6 to 7. If necessary, adjust the pH level.
Check for perennial noxious weeds! Determine if the site contains weeds such as nutsedge (Cyperus spp.), quackgrass (Elytrigia repens), bermudagrass (Cynodon dactylon), or Johnsongrass (Sorghum halepense). If present, they must be eliminated before any ornamental plants, including flower bulbs, are used. Consult Part A - Section D.3 for advice on weed control.
Check for proper light conditions! Depending on the genus, flower bulbs perform optimally under different light conditions. When De Hertogh and Le Nard (Chapter 6, The Physiology of Flower Bulbs, 1993, Elsevier Science Publishers, Amsterdam) reviewed the literature on light requirements for outdoor usage of flower bulbs, they proposed that five classes be used. This system is used in this Bulletin. The five light conditions are defined as follows:
The higher light intensities are preferred for Northern Climatic Zones (3 to 6) and the lower light intensities for Southern Climatic Zones (7 to 11).
Microclimates
A microclimate is the local modification of the general climate that is imposed
by the special configuration of a small area. It is influenced by topography,
the ground surface and plant
cover, and man-made forms. Knowledge of the microclimate can give important
clues for changing the prevailing climate in a favorable way. An illustration
is the microclimate produced by screening with tall evergreens that provide
a windbreak or shade. Another is the difference in an environment on the south
side of a building versus the north side. Lastly, the influence of planting
next to a heated basement versus an isolated planting bed can affect the flowering
date. Plants can alter the form of the surface, increase the area for radiation
and transpiration, shade the ground, change air movements, and trap air. All
these factors cause a cooler, more humid, and stable microclimate. Gardeners
and landscapers must consider these subtle changes when they select spring bulbs
for specific locations. This is particularly critical for many bulbs, e.g.,
tulips, for USDA Climatic Zones 7 to 10.
Design Considerations
The design effect to be created requires careful consideration when making
bulb selections. This includes factors such as:
Table 1 is divided into five flowering periods: very early (VE), early (E), medium (M), late (L) and very late (VL). Species for each flowering period are listed along with salient characteristics, such as color range, plant heights, etc.
Generally, there are several uses for spring flowering bulbs and most are suitable for two or more. The terms used are described below:
Bed - A large or small cultivated area constructed solely for the purpose of growing ornamental flowers and/or plants, including bulbs. Plants of a given cultivar are generally closely spaced in groups.
Border - A small strip of land in the foreground of an area in which ornamental flowers and/or plants are planted or a wide strip which contains flower bulbs, herbaceous perennials, annuals, ornamental grasses, and woody plants and is called a "Mixed Border".
Cut Flowers - Plants that provide floral spikes suitable for use as either fresh cut or dried flowers.
Exhibition Bulbs - Species and/or cultivars which produce large, majestic flowers and which do well either singly or in small group plantings.
Ground Covers - Species which can be readily perennialized in combination with low growing evergreen plants, e.g., English ivy, 'Blue Rug' juniper.
Lawns - Species which can be perennialized in lawns (usually selected from the VE and E flowering periods) and which flower well before the grass requires regular cutting.
Meadows - An area of grassland in which flowers are allowed to naturalize.
Rock Garden - An area where plants are cultivated with rocks. Plants must be adapted to terrain with shallow pockets of soil, extreme temperature fluctuations and water channeling.
Woodland Gardens - Areas in which species can be planted on the border of or amongst shrubs and trees. They normally flower early in the season (flowering periods VE and E) before shrubs flower and deciduous trees leaf out.
There are several ways to camouflage or reduce the negative impact of senescing bulb foliage. These include:
When the bulb foliage becomes distracting, simply lift the sprawling branch of the shrub upward so the bulb leaves will be under the shrub cover. When developing a garden plan that includes spring flowering bulbs, it is advisable to "Think Spring in Spring". At this time, the most obvious needs can be identified and the area of beds can be photographed for referencing when the garden plan is modified. For additional information on design considerations, consult the books by Hansen and Stahl (1993) and James (1991).