How To: Install bulbs
There's nothing quite like the burst of color that spring bulbs provide. Bold and beautiful, these show-offs provide vibrant spring color to help your clients cure their winter blues. For repeat customers, they help start the year off on a good note, with a splash of color that says, “Hey, the efforts of our company are making your life better.” Like any other ornamental planting, to produce positive results, it takes a little planning and creativity.
Classic uses of bulbs
By their very nature, bulbs are attention-getters. Many locations in the landscape benefit from focus and accent, such as the main entrance to a shopping mall, along the cart path to the #1 tee on a golf course or the front door of a home. When used correctly in mass and contrast, these plants direct the view of visitors and provide appeal for the owner as well. Realtors report that a house or commercial property with well-placed spring bulbs is much easier to sell than one that sits waiting for the installation of annuals until the threat of frost is past.
In addition to enhancement of “open” or stand-alone areas, bulbs serve as the perfect understory plant material for spring color. In the summer landscape, the presence of shade-tolerant shrubs, perennials and groundcovers offers depth to space under deciduous trees. Because these plants generally leaf out about the same as trees, however, they may offer little in the way of early spring appeal to the landscape. Bulbs offer bright splashes of color and texture when many other plants are still dormant.
Successful bulb plantings require proper installation and care. But it all begins with a good design. When designing with bulbs, you must keep several key factors in mind. The first and foremost is massing. There is nothing weaker from a design perspective than a line of widely spaced tulips along a pathway or foundation. Instead of adding color to a large area, this approach dilutes the color so that it is no longer an enhancement. If your resources are limited, design smaller beds with the bulbs grouped together, and place them strategically in the landscape. Fewer masses of plants offer much more impact than scattered bulbs or narrow lines of bulbs that wind through the space.
For permanent plantings, ensure that you choose bulb species that naturalize. Many varieties do not rebloom reliably in subsequent years (certain tulips, especially). This is no problem for one-shot plantings, but you'll do better with other types if you're planning on a permanent planting.
Landscape “depth” is an important design principle. Landscapes with a groundcover next to perennial flowers or shrubs that grow in the shade of large trees offer a complete and finished look, serving to soften corners and provide opportunity for integration of color, texture, form and function with human activity. Just as it is important to design a landscape with several different heights or levels of plant material, you should strive for a similar effect with the planting of bulbs. Plan to use the technique of gradation — bulbs of increasing sizes next to one another — to enhance depth and rhythm in the early spring landscape. The most common approach is to place the larger bulbs, such as tulips and daffodils, towards the back of a planting, with hyacinth and grape muscari as mid-level plants and crocus in the foreground.
It's one thing to use color, and quite another to use it well. For the most part, classic and formal bulb displays are best designed with multiple rows or masses of single colors that make a statement. The use of multi-colored plantings can be distracting to the eye unless careful thought is given to the colors. Bi-color displays are quite striking, as long as you use colors with strong contrast (blue-yellow, red-green and purple-orange). When you mix three or more colors between or within masses, consider using “similar” colors (i.e., use all pastels or all bright colors, all “hot” or all “cold” colors).
Another strong design principle that makes sense for bulbs is repetition. It's a strong part of unity, a classic design concept that ensures everything “fits together” and makes sense in a landscape. The best way to repeat with bulbs is to use similar color or texture masses in various or notable parts of the landscape, such as at the front entrance, the mailbox and in the understory at the corner of a house or building. In general, informal designs should use the “unity of three” principle, in that the repetition should be in odd-numbered masses (3, 5 or 7), while formal displays should contain even-numbered groups.
- Bloom time
Because most bulb blossoms last only a few weeks, try to incorporate several bloom dates in your design. With the cultivars that are currently on the market, it's quite possible to plant early, mid-season and late-blooming tulips and daffodils. Most of the other species provide less range in bloom times, but offer more flexibility than you might think. With a little homework, bulbs can be on display for several months in most areas of the country. Additional season length can be created by combining bulbs with other cool-season flowers, such as violas, pansies and ornamental kale. These offer similar advantages in terms of early spring color.
- Put it on paper
Get started with your design by using a “bubble diagram.” This is a simple, straightforward process for defining the spaces where bulbs will be planted. Again, there are differences between formal and informal designs. Formal displays are reflective of landscapes in the Middle Ages. European and Mideastern monasteries, palaces and cloisters were adorned with these types of plantings. In a formal design, straight lines and geometric shapes predominate. The bubbles on your first drawings would reflect these shapes. It's quite common to see linear displays on either or both sides of clipped boxwood, juniper or holly hedges, as the evergreen plant material reinforces the formality of the design, especially when two or more sizes of bulbs are planted. Another classic example is a low-medium-low planting that surrounds a rectangular reflecting pool.
Informal designs have historic origins as well. Trade with the Orient in the 1700s introduced the concept of “symbolic naturalism.” These Japanese and Chinese influences resulted in the naturalizing of bulbs beneath trees, along paths and in free-form drifts and clumps on hillsides. Bubble diagrams for informal displays would, of course, be more “free-form” in shape. Ovals, kidneys and circles are common in these designs.
- Site and soil
The installation of bulbs is similar to other ornamental plants in terms of site and soil. Getting to know the site is paramount to success with spring flowering bulbs. Many factors affect the success of bulbs, but the one that is probably most important is sun exposure. Bulbs generally need a minimum of 6 hours of direct sunlight after the foliage emerges to ensure vigorous plants, strong blooms and energy storage for the following season. Visit the area at several different times of the day to get a feel for the number of hours of sunlight it receives.
Understory bulbs will still receive sunlight before the trees leaf out, so consider the time of year when you're assessing the site. Also remember that bulbs used for just one bloom, such as tulips in a formal planting, should provide an adequate bloom even in some shade. You don't need to worry about growth and food storage for the following year if you're just going to discard the bulb after it blooms.
Sun exposure is not the only site-related issue to look at. It's also critical to consider the prevailing winds, other nearby plants and the soil conditions. While certain bulbs may prefer sunnier or shadier conditions, variability is not the case with drainage. All bulbs require good drainage. If soil tests of the site indicate a heavy clay content, then modify it with liberal additions of compost. This material has the magical quality of loosening heavy clay or silty soils, yet providing water-holding capacity to sandy, excessively well-drained soils. In severe cases of poor drainage, you may need to install an underground drainage system.
- Planting depth
Proper depth is crucial to the long-term success of the planting. If planted too shallow, bulbs may not survive the cold temperatures of winter. Deeper-than-recommended installations may result in weak, spindly stems or root rot. Fortunately, due to a close relationship between the Netherlands Bulb Information Center and bulb suppliers, guidelines for each species are widely available. In general, the larger the bulb, the deeper it should be planted, but check for planting depths specific to the species you're using.
As mentioned, liberal additions of compost or other organic matter are helpful in establishment. So, excavate the planting area, amend the soil and lay out the bulbs. To achieve the straight line and geometric style of a formal design, use stakes and string to align the bulbs according to the lines of the landscape design. Be sure to keep the recommended spacing in mind when you place the bulbs.
For informal designs, use landscape marking paint to spray out a shape on the soil and then evenly distribute the bulbs in the shape. Another popular approach is to simply toss them into the shape, and plant them where they fall for a more natural effect.
Your designs don't have to be one-shot, one-bloom displays. Plan some multi-season or extended season appeal with multi-species plantings. Install the bulbs that require the deepest planting first, such as daffodils or tulips. Next, backfill with about 3 to 4 inches of amended soil over the tops, and add some snowdrops or hyacinths. Place more soil over these and finish the job with grape muscari or crocus. Of course, make sure that the bloom sequence of the bulbs doesn't overlap too much. An added benefit of this approach is that the unattractive foliage of a short, early bloomer (such as crocus) will be hidden by a later blooming tulip.
Once the glory of the blooms have faded, some simple maintenance steps will keep a permanent planting attractive for many years to come. Post-bloom care is largely dominated by five procedures: deadheading, dealing with fading foliage, transition to annuals, weed control and fertilization.
After the blossoms have faded and the petals are dropping, remove the flower stems. This removes the unattractive stalks and allows the plants to redirect resources back to the bulbs for stronger regrowth the following year. Otherwise, some resources would be devoted to ripening unwanted seeds.
- Fading foliage
The next plant parts to fade are the leaves. They remain green for several weeks after bloom, making and storing food. Eventually, they will begin to turn yellow and brown. At this point, you have a couple of options. You can use rubber bands or twist ties to gather the foliage together, which minimizes the ugliness of the display, while keeping the leaves at least partly exposed to sunlight. The other possibility is to simply remove the foliage altogether, opting for a cleaner looking bed.
Your choice in leaf removal may depend on what is planted in the bed afterwards. In the transition to annuals, bundled up bulb leaves may get in the way of planting summer bedding. When installing the summer material, take care not to injure the spring bulbs remaining in the ground. Be sure to plant a bit off to the side of the bulbs rather than directly on top.
For annual bulb plantings — in those beds that get a fresh rotation every season — you have two choices; either dig up the bulbs and remove them, or spray them with a systemic herbicide and leave them in the ground. Either way, you want to be sure leftover bulbs do not regrow, with or without flowering, because this will interfere with subsequent planting designs.
- Weed control
Once the next set of plants are in, weed control and fertilization become important. An attractive organic mulch will go a long way towards suppressing weeds. If weed pressure has been heavy in previous years, consider an application of a pre-emergence herbicide.
If you have amended the bed as described for the planting of the bulbs, then the fertility level of the soil should be quite good. However, after you remove the flower stems, it is a good idea to take a soil sample. It is better to know fertilizer requirements than to guess at them. Adding only the needed nutrients in the right amounts will ensure good plant growth without risking overapplying any material.
John C. Fech is an extension horticulturist and Steven N. Rodie is an associate professor and extension landscape specialist, both with the University of Nebraska (Lincoln, Nebr.).
DON'T WORRY ABOUT REGIONAL DIFFERENCES … JUST CHILL!
Some factors affect all bulb plantings, and others are region-specific. So it pays to know what matters in your region. The factors that tend to be regional in nature are soil pH, soil fertility, the number of days of frost in the soil and planting date.
In general, soils in the eastern United States tend to be acidic, with those in the Midwest being slightly alkaline and the West quite variable. Soil tests will indicate the need for additions of lime and sulfur to correct the pH to a desirable neutral-to-slightly-acidic soil.
An interesting artifact of tradition should be noted: For years, many popular magazines and gardening texts have extolled the virtues of adding bone meal. If you look closely at where they are published, you'll notice that most of them are in the eastern United States. This explains the bias towards adding bone meal, which increases soil pH when incorporated. The bottom line: run a soil test, and make adjustments accordingly. It's possible that bone meal could run counter to the actual needs of your soil.
With the exception of paper white narcissus, most bulbs need 4 to 8 weeks of exposure to soil temperatures below 45°F in order to bloom. This poses a problem in the South, where this requirement often isn't met. Thus, perennial bulb plantings are not always successful in the South. Annual displays are, of course. But you must make sure you obtain “pre-chilled” bulbs from your supplier (or chill them yourself).
Spring flowering bulbs should be installed prior to soil freeze-up, but after the heat of summer is past. In general, mid-fall is best, but soil freezes at different times depending on your latitude and elevation, so plan accordingly.
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