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What Are Bulbs?
A bulb is a rounded part at the base of certain plants’ stems that stores energy while the plants are dormant—think of a bulb as a giant seed that the plants grow back from year after year. At the center of the bulb is the plant shoot itself, surrounded by layers of fleshy scales and connected at the base by a compact stem called the basal plate. The plants that grow from these bulbs are called “bulb plants,” or even simply “bulbs.”
Corms, tubers, tuberous roots, and rhizomes are all bulb-like storage organs but are not true bulbs. However, many gardeners still refer to these plants (like peonies, dahlias, daylily plants, begonias, cannas, anemones, ranunculus, elephant ears, and freesia) as bulbs, and they even share similar planting methods.
Types of Bulbs: Spring vs. Summer
There are two main types of bulb plants:
- Spring bulbs. Spring-flowering bulbs bloom in early spring, but they require at least a few weeks of cold weather to bloom. These hardy bulbs benefit from their time in the cold winter soil and should be planted in fall to give them time to settle before spring. When spring bulbs’ foliage wilts in the summer or fall, you can trim away some of the dead plant matter, but leave the bulbs in the ground to bloom and naturalize (or spread new plants) next spring. Spring-blooming bulbs include tulip bulbs, Narcissus (daffodils), Fritillaria, Muscari (grape hyacinths), alliums, crocuses, Scilla, Galanthus (snowdrops), and Hyacinthus orientalis (Dutch hyacinths).
- Summer bulbs. Summer-flowering bulbs are more delicate than spring bulbs and cannot survive underground in the winter. When the ground freezes, these tender summer bloomers may rot if left in the ground. After the growing season, once tender summer-flowering bulbs have wilted in the fall, dig them up before the first frost and store them indoors in a dry place during their winter dormancy. Summer bulbs include Amaryllis, calla lily bulbs, and Gladiolus.
When to Plant Bulbs
The best planting time for bulbs depends on the type of bulb you plan to grow:
- Plant spring bulbs in the fall. Since spring bulbs require a few weeks of winter weather to bloom, their best planting time is in early fall when soil temperatures cool to 60 degrees Fahrenheit; in the United States, this can be anywhere from September to November, depending on where you live. By planting your spring bulbs in fall, they’ll have plenty of time to establish roots and settle in for the winter, and they’ll start to bloom happily as the weather warms for spring.
- Plant summer bulbs in the spring. Summer bulbs can’t handle freezing weather, so the best time to plant them is in early or late spring or even early summer to give them time to establish roots and bloom in the warm summer weather.
How to Plant Bulbs
While there are many different kinds of bulbs, most are easy to grow and share similar planting methods. Once the weather is right in your area, you can begin planting bulbs.
- Choose the site. Flower bulb plants bloom best in full sun, so choose a spot that gets at least six hours a day in the spring; in partial shade, your plants may not bloom as much and will instead grow more green leaves.
- Prepare the soil. Well-draining soil is crucial for keeping your bulbs healthy—while they can handle brief droughts, they are much less tolerant of soggy soil and may rot if the soil stays too wet.
- Dig holes for your bulbs. Before planting, dig holes in each area where you want to plant a bulb, keeping at least three inches between them. The depth of the hole depends on the bulb; read the package or look online for planting instructions for your particular bulb. To plant many bulbs in a line, dig an entire row to plant along. When planting indoors, you won’t have to bury your daffodils as deeply in the soil. Simply, create a hole where that allows you to half-bury your bulb in the soil.
- Plant and mulch bulbs. When planting bulbs, place the bulbs pointy-end-up in the holes (this is the end that will sprout leaves). Cover with soil, and add a layer of mulch to help insulate the soil, discourage weeds, and retain moisture. If you’re planting the bulbs in pots, simply place the bulb pointy-side-up in the pot and half-bury it with soil.
- Water. Water immediately after planting to settle the soil around the new bulbs. Water once a week for about four weeks to encourage root growth.
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