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Brimming With Bulbs: Container Gardens That Capture the Essence of Spring
by Mark Fisher
After a cold, dark winter, we all long for a sign of spring—even something as subtle as a crocus bloom peeking through the snow or the delicious smell of a hyacinth on a bright, cool spring morning. You can capture a little bit of that spring feeling by filling containers, whether barrels, buckets, boxes, pots, jars, or troughs, with spring-flowering bulbs. Pots of spring bulbs expand your garden space and allow you to extend the bloom season in a protected spot on the patio or terrace.
Container Choices
The first step is finding suitable containers. The styles and sizes you choose will form the framework of your design and determine whether your bulb display has a formal, informal, or eclectic feel. I prefer containers made of fiberglass, heavy plastic, or wood to those made of clay, which tend to crack easily if exposed to alternating freezing and thawing during the winter.
No matter what style or material strikes your fancy, be sure to pick pots that are at least 16 inches across and 12 inches deep. The containers need to be large enough to give the bulbs room to develop strong root systems, which will keep them from being forced up and out of the soil as it freezes in winter. The larger the container, the longer the soil will stay moist, and it may not even freeze solid during the coldest days of the year. Adequate drainage holes are another important consideration. A container that's 18 or so inches across should have at least three holes about half an inch wide. Larger containers, 24 inches or more across, often have one 1-inch hole, usually in the center of the base.
A strawberry jar planted for spring: The flowers of Tulipa tarda rise above the top, while the foliage of spent crocuses peeks from the pockets.
Potting Soils
Once you've assembled the containers, it's time to consider the planting medium. Bulbs generally require soil that drains well and retains moisture; they are prone to rot in soggy or heavy soil. The ideal container mix absorbs water quickly and holds its shape when you take a handful and squeeze it.
You can make your own planting medium by mixing compost with sand in a ratio of 2 to 1, or you can use a commercial mix. As most of these are peat-based, they have a tendency to hold a lot of water, so it's usually a good idea to amend them with a little coarse sand to promote drainage. Avoid potting mixes that contain a lot of perlite. Over time the white pellets tend to float to the top of the container, where they look a little out of place.
Bulb Combinations
When it comes to choosing plant combinations for containers, you have tremendous latitude. You can base your design on combinations of colors, bulb varieties and heights, bloom times, and fragrance.
Color sets the mood of your design. Tulip combinations such as purple and orange or red and yellow are brilliant and eye-popping. You can use dark-flowered tulips with taller varieties in lighter shades for a nice effect. Monochromatic schemes using different bulb varieties can create an interesting effect, or you can go for high contrast by mixing white flowers with very dark ones. For a whimsical touch, mix tall, dark maroon varieties with shorter yellow varieties. Plant individual containers with one variety, or mix different bulbs in one pot and group them together.
Choose plants with different blooming heights to give accent and dimension to your composition. One common approach is to plant tall flower varieties toward the center of the container and surround them with shorter plants. If you have a pot that's at least 30 inches across, try planting three groups of taller varieties using five to seven bulbs per group. For example, mix different classes of tulips, such as doubles and single- or lily-flowering varieties. A short pink double tulip planted with a mix of pink lily-flowered tulips and pink Darwin hybrids makes an appealing combination.
No matter what style or material you pick, be sure to choose a pot that's at least 16 inches across and 12 inches deep, so the bulbs have enough room to develop strong root systems. The barrel above is planted with daffodils, tulips, and grape hyacinths.
You can lengthen the bloom season by combining bulb species with different flowering times, all in one pot if you like. As one variety fades, another starts to bloom. This approach requires you to imagine how your composition will unfold over time. Remember that as the blooms of the earlier varieties fade, they will leave their foliage behind. It's a nice idea to soften the coarse foliage of tulips by mixing them with crocuses, which have attractive, grasslike leaves.
Develop a focal point for each container that changes as the season progresses, otherwise you may end up with a "hole" in your design. With careful planning you can create several different combinations that will keep your pot flowering for two to three months. Start your container blooming with early-flowering species crocuses such as Crocus chrysanthus, C. ancyrensis, and C. tommasinianus. As these fade, early varieties of fragrant narcissus or tulips start to open, then wonderfully fragrant hyacinths, followed by later varieties of narcissus and tulips, which will bloom into late May.
Planting the Containers
Once you've determined how you want to combine plants, you are ready to start potting. Spring-flowering bulbs need to be planted in the fall when cool soil temperatures—about 40°F—will prompt rooting, which takes four to six weeks. This means that if you live in the Northeast, for example, you should plant bulbs in pots in early October, about when you remove summer annuals from containers. Most bulbs also require a cold period of about 12 to 16 weeks to get properly established (the length of the cold period varies, depending on the species).
Plant larger bulbs first. Fill the soil level in the container to the correct planting depth for the large bulbs. If you start with tulips, for example, fill a container that's 12 inches deep with 6 inches of soil. Place the bulbs on top of the soil and cover them with about 3 inches of soil. Then plant the smaller bulbs at this level and cover with additional soil.
The rule of thumb is to plant bulbs at a depth three times the diameter of the bulb. In other words, plant tulips, narcissus, and hyacinths about 4 to 6 inches deep measured from the base of the bulb and smaller bulbs such as crocuses, anemones, and glory-of-the-snow (Chionodoxa) 2 to 3 inches deep. For a lush look, set the smaller bulbs close together, just 2 to 3 inches apart. Space larger bulbs 6 inches apart.
When planting tulips, you will notice that one side of the bulb is flattish and the other side more rounded. If you are planting tulips around the edges of a container, turn the bulbs so their flat sides face the wall. As the tulips emerge in spring, the first leaf will unfurl toward the flat portion of the bulb and over the edge of the pot, softening it. With other bulbs, just be sure to plant them with the pointed end facing up. Once you've planted all the bulbs, water them thoroughly. Depending on the size of your pot, you may have to water weekly to keep the soil evenly moist.
When winter arrives, mulch the containers with a 3-inch layer of leaves, shredded bark or coco, or evergreen boughs left over from the holidays (you can pile the branches about 5 inches thick). Mulching will reduce the effects of repeated freezing and thawing, which commonly occurs in early spring and may push the bulbs out of the soil.
Check the container periodically throughout the winter to be sure that the soil is moist—and so that you can witness the emergence of the bulb buds. Start removing most of the mulch when the plants are about an inch tall. Leave a 1-inch layer of bark or coco mulch on the soil to give the container a finished look.
By the time the last of the spring-flowering bulbs fade, the warmer weather will have arrived, and you can start planting your containers with summer flowers.
Mark Fisher has been working at Brooklyn Botanic Garden since 1984, when he started as an instructor in the Education Greenhouses. In the following year he became the curator of the Desert House. Since 1996, Fisher has been the foreman of the Steinhardt Conservatory. He holds a B.S. in Ornamental Horticulture from Colorado State University and has a lifelong interest in gardening and growing bulbs.
Photos: Derek Fell