Planting bedding plants directly on top of bulbs is a common and effective layering technique used to ensure continuous color in a flower bed. This method typically involves spring-flowering bulbs, such as tulips and daffodils, beneath shallow-rooted annuals that provide summer interest. This combination allows a seamless transition from the spring bulb display to a vibrant summer garden. The annuals fill the space and mask the dying foliage of the spring bulbs as they enter dormancy.
Coordinating Bulb and Bedding Plant Cycles
The timing of planting bedding plants depends on the spring bulb’s natural life cycle. Spring bulbs, such as daffodils and hyacinths, require a period after flowering to store energy for the next year’s bloom. This energy-storing process happens in the foliage, which must be left intact until it naturally yellows and dies back. This can take anywhere from six weeks to a couple of months following the end of the bloom period.
Wait to introduce summer annuals until the bulb foliage is visibly fading or has been cut back after fully yellowing. Planting annuals too early risks damaging the green bulb leaves, interrupting the photosynthesis process and weakening the bulb. This interruption can result in a reduced flower display the following spring. By late spring or early summer, when the bulb foliage is nearing its complete die-back, conditions become ideal for planting the summer annuals.
Techniques for Safe Installation
Avoiding physical damage to the dormant bulbs is the primary concern when planting annuals above them. Spring bulbs are usually planted deep enough that shallow-rooted annuals can be installed safely above them. Use a small hand trowel, not a large spade or shovel, for digging the planting holes for the annuals.
Dig carefully and shallowly, creating a pocket just large enough for the bedding plant’s root ball. Position the new plants in the spaces between the known locations of the dormant bulbs, rather than directly over them. If you encounter resistance while digging, stop immediately and shift the planting spot slightly to avoid piercing the bulb, which can introduce disease or cause rot. Leaving a short stub of the yellowed bulb foliage can also serve as a visual marker to help you avoid the exact location of the bulb.
Selecting Complementary Plants
Successful layering requires selecting annuals that thrive in the same conditions as the underlying bulbs without aggressive competition. The most suitable bedding plants have shallow, fibrous root systems that will not penetrate deep into the soil where the bulbs are resting. Excellent choices include:
- Impatiens
- Petunias
- Sweet alyssum
- Pansies
Matching the light and water requirements between the two layers is important for a thriving display. If the area receives full sun in the spring, select summer annuals that also prefer full sun. If the spot becomes shaded by nearby trees in the summer, choose shade-tolerant annuals. Selecting annuals with low to moderate water needs is beneficial, as excessive moisture can lead to rot for the dormant bulbs below.
Post-Bloom Care and Maintenance
Once the bedding plants are installed, maintaining the proper moisture balance is important for the health of both layers. The annuals require consistent watering throughout the summer, but the dormant bulbs beneath need a relatively drier environment to prevent fungal diseases and rot. A targeted watering approach, focusing water directly on the annuals’ root zones, helps satisfy the summer plants without unduly saturating the deeper soil.
It is necessary to leave the bulb foliage intact until it becomes completely brown and withered, even as the annuals grow around and over it. This yellowing process is the final stage of the bulb’s vegetative cycle, where the leaves transfer stored energy from photosynthesis back into the bulb for the next season’s bloom. Prematurely cutting the green foliage severely depletes the bulb’s energy reserves. Light fertilization with a balanced fertilizer is acceptable for the annuals, but avoid high-nitrogen formulas, as they can encourage excessive foliage growth on the bulbs at the expense of flower production.