Growing blooms from bulbs is one of the easiest ways to enliven your garden.
They’re in the ground beneath our feet, waiting for warmth to rouse them from sleep. As soon as the days lengthen, the first green spears will emerge: winter aconite and snowdrops, followed by crocus, daffodils and anemones. As the season progresses, tulips, lilies and crocosmia dapple the landscape. We welcome them every year.
Bulbs are a mainstay of our garden thanks to their easy care and varied blooms. We grow them for scent, cut flower bouquets, and local pollinators, but with thousands of varieties to choose from, it can be hard to know where to start. Read on to learn some of the lessons we’ve gleaned over 40 years of growing bulbs in the garden.
What are botanical bulbs anyway?
Bulbs are essentially underground storage systems that contain all the nutrients and energy needed by a plant to grow, bloom, and survive through the dormant season. The main types of bulbs and bulb-like structures include:
- True bulbs: The most familiar type of bulb, true bulbs contain layers, an embryonic shoot, and a protective outer covering. Examples include tulips, daffodils, lilies, and onions.
- Corms: While corms look similar to true bulbs, they lack layers. Instead, they consist of a dense, fleshy mass that gets used up and replaced each season by a new corm that forms on top or beside the original. Common plants that grow from corms include crocuses, gladiolus, and freesias.
- Tubers: The humble potato is probably the most famous tuber. These contain a thickened, underground stem that has multiple growing points, or “eyes,” from which new shoots emerge. Tubers do not have a protective outer covering and can sprout from several locations. Dahlias and begonias are two other well-known examples of tubers.
- Rhizomes: Unlike true bulbs, corms, or tubers, rhizomes spread laterally rather than growing downward, allowing plants to colonize new areas via an underground stem that sends up new shoots and roots along its length. Common plants with rhizomes include irises, ginger, and canna lilies.
Choosing the right bulbs for your climate
There’s nothing worse than planting bulbs in the ground, only to have them rot away and never emerge. We’ve learned the hard way that some bulbs just don’t survive the winter in our area, and no amount of babying will help them live.
To choose the best bulbs for your growing zone, identify your USDA Hardiness Zone or equivalent climate classification to help determine which bulbs can survive your local winter temperatures. If you live in the USA, you can find your zone by using our growing zone maps.
Once you know your zone, check the recommended range for each type of bulb. Hardy bulbs, such as tulips, daffodils, and crocuses, thrive in colder zones and require a period of winter chill to bloom properly. Tender bulbs, like dahlias and gladiolus prefer warmer climates and may need to be dug up and stored indoors in colder areas. We now have a fall routine for digging and storing dahlias in our greenhouse, which keeps them safe and sound until springtime.
Understanding bulb seasonality
While bulbs are easy to grow, planting time is key. That’s because different bulbs need to be planted in different seasons to grow and bloom. Bulbs are not usually a ‘one-and-done’ proposition, though many will continue to rebloom year after year with little maintenance.
Bulb seasonality refers to the natural growth cycle of bulbs, including when to plant each variety, and when they bloom and go dormant. Different bulbs have specific seasonal needs based on their hardiness and growth habits.
Bulbs have seasonal needs based on their hardiness and growth habits. These dahlias are planted out in spring.
- Fall-planted (spring-blooming) bulbs: Bulbs like tulips, daffodils, crocuses and hyacinths require a period of winter chill to trigger flowering. Plant them in autumn, before the ground freezes, where they’ll remain dormant through winter. In spring, they’ll sprout, bloom, and then die back, storing energy in the bulb for the next year.
- Spring-planted (summer-blooming) bulbs: Plant warm-season bulbs like dahlias, lilies and gladiolus in spring after the last frost, when your soil has warmed. They’ll grow all through summer before going dormant in the fall. Many of these bulbs are tender and need to be lifted and stored in colder zones, as noted above.
- Summer-planted (fall-blooming) bulbs: A few bulbs, such as autumn crocus (Colchicum), are planted in summer and bloom in early to mid-fall. These bulbs thrive in warm weather but send up flowers as temperatures cool.
- Indoor and year-round bulbs: Bulbs like amaryllis and paperwhites can be “forced” to bloom indoors at any time of year by controlling their growing conditions. These bulbs don’t rely on natural seasonality and can be chilled or warmed to encourage blooming.
Designing with garden bulbs
We love adding new bulbs to our garden each year, but we try to keep three things in mind as we do this: color, height, and bloom time.
Color
Color helps determine the mood of a garden, with warm hues creating energy, while cool tones bring a sense of calm. When planning our bulbs for the year, we consider what’s already in the ground along with new plantings. Complementary or monochromatic color schemes offer a cohesive look, while bright contrasts can create focal points. One of our favorite design tips? Grouping bulbs of the same color in clusters prevents a scattered appearance.
Height
Height is another factor to consider if you’re going for layered, natural-looking arrangements. We use taller bulbs, such as alliums and fritillarias, for backdrops. Mid-height daffodils and tulips provide balance and splashes of color. Low-growing bulbs like our favorite crocuses, anemones, snowdrops and grape hyacinths work well along borders, pathways, or in front of taller plantings to create depth and dimension.
Taller blooms like these alliums make an excellent backdrop in mixed borders and foundation plantings. Photo by Thomas Brenac.
Bloom time
Bloom time is an important criteria if you want to create a garden that has something to offer across the seasons. We select a mix of early, mid, and late-season bloomers, as our bulbs bloom from early spring all the way through late summer. Snowdrops and crocuses provide the first signs of spring, followed by daffodils, alliums and tulips in mid-season. Lilies and gladiolus extend the display into summer. We particularly love the autumn crocus, which is one of the few vibrant flowers in our late fall garden.
Seasonal care and planting
Planting and caring for bulbs is a straightforward practice that relies largely on timing. Completing specific tasks each season has helped us enjoy colorful displays from the earliest frost to the beginnings of winter. The image below summarizes main tasks by time of year.
Best soil and fertilizer for strong bulbs
Since the variety of bulb you choose will determine its growing conditions, it’s best to follow the grower’s recommendations. Most bulbs prefer full sun and well-drained, nutritious soil, though there are bulbs suitable for shade (see chart below). We keep our soil healthy by adding compost twice each year. This helps maintain organic matter and keeps things well aerated.
When planting new bulbs, we like to add organic fertilizer high in phosphorus (e.g. rock phosphate or bone meal) to the planting hole. For best results, feed new and established bulbs with a high-potassium liquid fertilizer (e.g. liquid kelp) every two weeks during the growing season until the foliage starts to die back.
Planting depth and spacing
Planting depth will vary depending on the bulb type, but a good rule of thumb is to plant bulbs two or three times the bulb’s height. This helps insulate them during the dormant season and protect them from pests. If you are in a cold climate, stick to the deeper end of the range.
Space bulbs according to the grower’s recommendations. In general, bulbs like tulips and daffodils need 3 to 6 inches of space between, while smaller bulbs like crocuses and snowdrops need 1 to 3 inches. Crocosmia corms, while small, do best when planted 6 to 8 inches apart.
Harvesting, cutting back and storing
To preserve bulb longevity, avoid cutting and removing plants until they fully die back and the year’s nutrients have had a chance to return to the bulb. This usually takes about six weeks after blooms are finished. We interplant clusters of daffodils with daylilies, whose leaves flesh out just as the daffodils are finishing. Offsetting bloom times in this way helps conceal aging plants.
Deadheading blooms in season will keep plants fresh. This enables true bulbs and corms to store up energy and promotes further blooming in most tubers and rhizomes.
Allow daffodils to fully die back before removing spent foliage Photo by Ginger Jordan.
When the season inches towards your first frost date, dig up tender bulbs, shake off excess soil, and place in a dry, cool space. We store our tender bulbs and tubers underground in greenhouse beds where they seem to love the temperature and humidity, but colder areas would require taking them indoors. Many gardeners find growing tender bulbs in containers makes this transition easy.
During the dormant season, check periodically for wizening or rot. Adding a storage medium like sawdust or peat moss to stored bulbs can help maintain moisture and fend off fungus. Hardy bulbs can stay in the ground all year round.
Dividing and naturalizing bulbs
If some of your true bulbs and corms appear overcrowded after they flower, that’s the signal to divide them for future growing seasons. Once the foliage has died back, gently dig them up, separate them, and replant farther apart. Over time they will establish new colonies, naturalizing across the garden. Dividing every three to four years is often a good practice. Good candidates include daffodils, crocuses, tulips, lilies, irises and hyacinths.
Divide tubers before replanting in the springtime when the eyes are most visible. Separate large masses into smaller clumps. Dahlias, for example, will regrow as long as enough crown remains on the new tubers and no rot exists.
Troubleshooting common issues when growing bulbs
Although they grow from small corms, crocosmia plants require 6 to 8 inches of space to thrive.
My bulbs won’t sprout.
This issue can occur if you plant your bulbs too deeply, too shallowly, or in an area that doesn’t drain sufficiently. Review the grower’s instructions at planting time and ensure your soil drains well year round. If it doesn’t, consider growing your bulbs in raised garden beds. Also be sure to buy only viable bulbs. At times, dried out or diseased bulbs can also be the culprit.
My bulbs come up, but they are weak or spindly.
Bulbs need sufficient sunlight to develop robust foliage that will support blooms. While woodland bulbs thrive in dappled shade, most common garden bulbs need at least six hours of sunlight each day to thrive. If this isn’t the issue, consider overcrowding and depleted soil. Space bulbs according to the grower’s instructions for best air circulation and fertilize at planting time and throughout the season.
Pests are eating my bulbs.
Squirrels, voles, and other rodents may dig up and eat bulbs, or move them around for eating later. (Our daffodils have shown up in the strangest places.) If this happens repeatedly in your garden, use wire mesh cages around bulbs when planting or consider planting pest-resistant bulbs like alliums and snowdrops.
My bulbs aren’t blooming.
If you cut the foliage of your bulb plants too after flowering, they may not retain enough nutrients to bloom the following year. That doesn’t mean you can never enjoy cut flowers indoors, but take care not to overharvest any one plant when making your bouquet. Similarly, avoid cutting back foliage until it fully dies back. If the problem persists, check your soil for lack of nutrients or consider overcrowding.
Growing bulbs for beauty and ease
Growing healthy and beautiful blooms from bulbs involves choosing the right varieties for your garden and providing regular care according to each season. We’re always thrilled when new bulbs we’ve added to the mix come up for the first time: that extra touch of color and vibrancy never gets old. They’re also some of our lowest maintenance plants while offering the most enjoyment.
