Spring-Flowering Bulbs

Spring-Flowering Bulbs

  • By Pat Chadwick
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  • October 2015 - Vol. 1 No. 10
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  • 0 Comments

by Pat Chadwick

One of the best investments a gardener can make is in spring-flowering bulbs — the easiest and most dependable ornamental plants to grow. Depending on the species, bulbs will bloom and multiply for years, decades even, making them a very inexpensive investment over time. Ah, but it’s autumn and you’re probably wondering why we’re talking about spring bulbs now. The reason is simple. When bulbs become available in late summer for fall planting, they look brown, lumpy, and totally uninteresting. Besides that, at this time of year, our gardening priorities are normally placed on fall clean up – not planting. However, autumn is precisely the right time to plant bulbs for an early spring garden because they need to undergo a long period of chilling in order to bloom. So, when it comes to bulbs, the idea is to PLAN in the spring or summer and PLANT in the fall.

ADVANTAGES OF GROWING BULBS

Spring-flowering bulbs are the earliest plants to bloom in the garden.   Depending on the weather, cold-hardy snowdrops and winter aconites make an appearance in February or March, often peeping through the snow. Crocuses soon follow, along with scillas and Chionodoxas. As spring arrives, daffodils and hyacinths emerge in March and April, followed by tulips and ornamental onions in May and early June. In other words, it’s possible to have a nearly continuous sequence of bulbs in bloom from the last snowy days of winter until the heat of early summer.

Bulbs are very versatile. They can be incorporated into perennial beds, mixed borders, foundation plantings and rock gardens. They can be planted along walkways and paths. They can be used in mass plantings, in drifts in large beds, or naturalized in woodland settings. They can be planted in frost-proof pots or forced into bloom indoors, but more on that later.

Once they’re planted, bulbs require little human intervention. After they finish blooming, they continue to grow and store food in their underground storage organs, at which point the foliage dies back to ground level. Once the foliage is dead, the bulb enters a period of dormancy until the following spring, when it repeats the cycle.

MAJOR TYPES OF SPRING-BLOOMING BULBS

Tulips, narcissus, and hyacinths are by far the most commonly used bulbs in the spring landscape. It’s not an exaggeration to say that they are the star attractions in the spring garden.

TULIP – Few sights are more glorious in the springtime than a mass planting of tulips. Images of this beloved spring favorite were portrayed on walls, vases, and other ancient artifacts dating back as early as 2200 B.C. and possibly beyond.  Its continued popularity over the centuries makes it one of the most easily recognized plant species in modern-day gardens. Whether your preference is for a stately formal planting or for a naturalized setting of tulips, many varieties and colors are available from which to choose. They are available in just about every hue imaginable and range in height from 6 inches to about two feet. Most tulip experts organize the species into 15 families or groups. Depending on the variety, the blossoms may be single, double, fringed, ruffled or even lily shaped. Smaller species tulips tend to be reliably perennial, while larger varieties may need to be replanted every few years or simply treated as annuals. You can extend the show by planting early, mid-, and late-spring varieties. One word of caution: deer typically avoid most spring-flowering bulbs, but they make an exception for tulips and can devastate an entire bed of them in one night. In my experience, deer have an uncanny sense of timing. They either ignore the foliage, or perhaps nibble at it, but then devour the flower buds just as they emerge.   Voles can also be a problem. To avoid vole damage, plant tulip bulbs about two inches deeper than normal (eight inches instead of the normal six).   This may delay blooming slightly but voles don’t like to go that far underground to feast.

Tulips in Mixed Border

Tulips in Mixed Border

 

NARCISSUS – Whether you call it Narcissus or daffodil, this dependable spring-flowering bulb is a favorite of gardeners everywhere. According to classical mythology, the name comes from the story of a beautiful youth, Narcissus, who fell in love with his own reflection in a pool. He stared at the image so long that he died and was transformed into a nodding flower. Despite the sad story behind its name, this cheery plant lights up the landscape in spring time. It offers up abundant blooms in yellow, white, pink, salmon, and various bi-color combinations. Daffodils range in height from 6 to 20 inches and grow singly or with multiple flowers per stem. According to the American Daffodil Society, the 13 families making up this genus consist of more than 25,000 registered daffodil cultivars. That’s impressive! The large-cup and trumpet daffodils are the ones with which most of us are familiar. But if you like to experiment, try growing some of the double and split-corona types or some of the many multi-stemmed and miniature cultivars that are available. Like tulips, daffodils may be selected for bloom times so that you can keep the show going from early to late spring. Because the bulbs are poisonous, mice and voles do not eat them. Squirrels sometimes dig up the bulbs but they don’t eat them.  Deer may occasionally “taste” the foliage but they don’t normally do any significant harm.

Daffodil 'Dutch Master'

Daffodil ‘Dutch Master’

 

HYACINTH –Many gardeners are drawn to hyacinths because of their intoxicating fragrance and because of their vibrant (some might say intense) colors, including many shades of pink, blue, yellow, red, and purple as well as white. The tubular, bell-shaped single or double flowers are either loosely or densely held on short stalks, depending on the cultivar. Hyacinths have a strong presence in the garden and are commonly used in large masses in formal bulb plantings. After a couple of seasons, the flower size may decline, in which case, you may want to plant fresh bulbs. After the flowers bloom in spring, the flower stalks should be cut back but leave the foliage in place to die back naturally.

Hyacinth-SkyJacket

Hyacinth ‘Sky Jacket’

 

EXAMPLES OF SPECIALTY SPRING-BLOOMING BULBS

While tulips, daffodils and hyacinths may be considered the crème-de-la-crème of spring-blooming bulbs, many lesser known or less showy bulbs are just as interesting. These “specialty” bulbs have slightly different growing requirements than the major bulb families, but they are also easy to grow. Some of the more commonly grown specialty bulbs include:

ALLIUM — In addition to culinary onions, shallots, leeks and chives, the Allium family includes a wide range of ornamental onions that add a pleasing architectural element to the ornamental garden. Most of the ornamental onion varieties have spherical flower heads on long stems that rise well above a clump of strap-like leaves.   The foliage of the early bloomers generally dies back just as the plants come into bloom. Foliage of alliums that bloom later in the season remains green and attractive much longer. Position the early bloomers in the landscape so that surrounding plantings hide the deteriorating leaves.

Allium 'Giganteum'

Allium ‘Giganteum’

 

CROCUS – The low-growing crocus can often be spotted emerging through snow in late winter or early spring. It is arguably the most anticipated of the spring-flowering bulbs. Of the more than 80 known species of crocus, more than 40 may be found in bulb catalogs. The most commonly planted crocuses are the Dutch hybrids, which bear larger blossoms than the species and bloom a little later. Their diminutive form and bright colorful blossoms make the crocus a welcome sight, especially when viewed in mass plantings. The colors range from lavender to purple, white to cream, and from yellow to orange. Because crocuses bloom so early, they are an excellent choice for naturalizing in the lawn. Over time, they will multiply to cover a large area. For best effect, they should be planted in groups of a dozen or more. If you’re interested in the saffron crocus, it is a fall-flowering crocus that is planted in spring.

Crocus

Crocus

 

CHIONODOXA – Commonly known as glory-in-the-snow, this bulb gets its name from its appearance in late winter to early spring. Planted in naturalized masses in rock gardens or in sunny lawns or partly shady woodland settings, it forms a carpet of color that mixes well with other early spring bulbs, such as snowdrops, daffodils, or species tulips. Each bulb produces a six-inch flower stalk topped by three to six star-shaped, upward facing violet-blue flowers with white centers.   This is one of the few plants that can tolerate juglone, a toxic substance produced by black walnut trees.

 Chionodoxa (Glory in the Snow)

Chionodoxa (Glory in the Snow)

 

GALANTHAS — Commonly known as snowdrops, these bulbs are some of the very earliest to bloom in late winter or early spring. The teardrop-shaped flowers are white with green blotches or stripes. They will grow in full sun but prefer moist, humusy soil in part shade. They are well suited for areas under deciduous trees where they receive full sun in early spring but part shade once the trees leaf out. Snowdrops are a good choice for naturalizing since they propagate by both self-seeding and bulb offsets.

Galanthus nivalis (Snowdrops)

Galanthus nivalis (Snowdrops)

 

MUSCARI ARMENIACUM – Better known to gardeners as grape hyacinth, this spring-blooming bulb features clusters of violet urn-shaped flowers on eight-inch tall scapes. The blossoms resemble a miniature bunch of grapes. When planted in masses, grape hyacinth forms a spectacular violet-blue carpet, which looks stunning paired with other taller spring bulbs. The vivid blue color blends particularly well with the saturated reds or yellows of tulips and daffodils. The foliage typically dies back after the plant finishes blooming. But, unlike other spring-blooming bulbs, this one produces fresh foliage in the fall which stays evergreen through winter. This is a popular container plant, which harmonizes well with other spring bulbs. It is also very easy to force into bloom.

Muscari armeniacum (Grape Hyacinths)

Muscari armeniacum (Grape Hyacinths)

 

SITE REQUIREMENTS FOR SPRING-BLOOMING BULBS

Bear in mind that bulbs are going to stay in the same spot for years – decades even. If the site meets their needs, the bulbs will reward you with good flower set and they will multiply well. If the site fails to provide a habitable environment, flower production will be impacted.  So, for best performance, choose a planting site that meets the following requirements:

  • Sunlight — The site should be sunny. While bulbs generally do well with 5 or 6 hours of sunlight daily, they will flower better if they receive 8 to 10 hours of sun.
  • Drainage — With the exception of Camassia, which prefers moist soil, spring-flowering bulbs require soil that drains well. Too much moisture can pack the soil tightly, which prevents the bulb roots from penetrating into the soil. Also, soil that is too moist will cause the bulbs to rot. To prevent this problem, make sure water drains away from the site. Depending on which bulb you’re growing, loosen the soil with a spade or garden fork to about 8 to 12 inches. The goal is to loosen the soil beneath the bulb roots. Work in organic matter, such as compost or well-rotted manure, which will also help the soil drain. This is particularly important if you have heavy clay soil.
  • Nutrients — A soil test will determine the pH and nutrient needs of the soil. Contact the Virginia Cooperative Extension office for information on how to test your soil. The soil test report will advise you on whether to add lime to increase the pH or fertilizer to correct any nutrient deficiencies.
  • Soil Preparation – Good drainage is the single most important factor to remember planting bulbs.   Otherwise, the bulbs will rot. Also, wet soil packs tightly and retards plant growth. Spade the soil about 8 to 12 inches deep, depending on which bulbs you are growing. The soil needs to be loosened at a depth below the bulb so that the roots can easily penetrate into the soil.   Incorporate compost or other organic matter and some 5-10-10 fertilizer (if needed) into the loosened soil. Make sure the fertilizer is well mixed into the soil. You do not want to place the bulbs directly on the fertilizer.  Follow the directions on the fertilizer to determine how much to add to the area.

PLANTING INSTRUCTIONS

Now that you’ve prepared the planting site, you’re ready to plant your bulbs.

  • Plant the largest bulbs available.  This is particularly true of tulips, daffodils, and hyacinths. Larger bulbs produce larger plants. Avoid “bargain” bulbs, which may be small, soft, damaged, or even moldy.
  • If you have a rodent problem, take preventative action when you plant bulbs. Mice and voles may eat bulbs. Squirrels may dig up newly planted bulbs but they don’t generally eat them. One solution is to place a chicken wire cage around the bulbs when you plant them. Commercially made cages are available but you can make your own. Another trick is to place a layer of sharp gravel around the bulbs in the planting hole.
  • Plant the bulb with the pointed end up. If you’re not sure, then plant the bulb on its side. The bulb will right itself in due time.
  • Most plant catalogs, on-line retailers, and garden centers provide instructions on how deep to plant bulbs. As a general rule of thumb, position the bulbs so that the soil above the bulb is about twice the diameter of the bulb. In other words, if the diameter of a bulb is two inches, then plant it four inches deep.
  • Space bulbs far enough apart so that they will have room to grow and multiply for several years before you have to divide them.
  • Unless you’re going for a formal look, plant bulbs in groups or clusters for a more natural look.
  • Cover the bulbs and water them well.

CARE AND MAINTENANCE

  • Deadheading – After the blossoms on spring-flowering bulbs fade, snip or pinch them off so that the plant doesn’t expend energy producing seeds.
  • Foliage – Leave the foliage in place until it dies back naturally. This may take six to eight weeks but it’s important to allow the foliage access to maximum sunlight so that it can continue to photosynthesize. Don’t braid the foliage or tie it in bunches with rubber bands.
  • Watering – Other than during prolonged drought periods, spring-flowering bulbs don’t normally need to be watered. Rain water is normally sufficient.
  • Fertilizing – Avoid using high-nitrogen fertilizers on bulbs. If fertilizer is needed, work a balanced fertilizer such as 8-8-8 or 10-10-10 into the top inch of soil, being careful to avoid contact between the fertilizer and the foliage or the bulb. Fertilize twice a year: just after the flowers fade and again in fall about the same time as you would normally plant new bulbs.
  • Mulching – Apply a two to four-inch layer of mulch over bulbs after cold weather arrives.
  • Staking – Most spring-flowering bulbs don’t need to be staked. However, if you live on a windy site, some of the taller tulips and ornamental onions may benefit from being staked. Be careful to avoid damaging the bulb when you insert stakes.
  • Dividing – Daffodils and other spring-blooming bulbs multiply freely, creating large clumps. When they become crowded, they don’t produce as many flowers, which is your cue that the clumps need to be divided. After the foliage has died back in early summer, carefully dig up the bulbs and separate them. Either replant them right away or store them until fall and plant then. If you store them, remove all excess soil, dry them and store them in a cool, dry place. When you re-plant the bulbs, give them plenty of space in which to grow and multiply.

MORE USES FOR BULBS

  • Forcing Bulbs – If you yearn for spring flowers in the dead of winter and you plan well in advance, you can force hardy bulbs into bloom indoors. Tulips, hyacinths, narcissus, and crocus are commonly used for this purpose. Snowdrops don’t respond well to being forced into bloom. It takes about three months wait time to force a hardy bulb into bloom. In other words, to have tulips in bloom in December, you need to prepare them for forcing in September. They require chilling (35 to 55°F) for a period of time before they can be forced into bloom. Not all bulbs need to be chilled in advance. Amaryllis bulbs and Paper White Narcissus are two popular bulb choices that may be successfully forced into bloom without being chilled. For more information on how to force bulbs, see Virginia Cooperative Extension Publication HORT-76NP referenced below.
  • Growing bulbs in pots You don’t necessarily need a garden in order to enjoy spring bulbs. To grow bulbs in pots outdoors, first choose a frost-proof pot that drains well. Plant the bulbs as deeply as you would if you were planting them in the ground. Make sure there’s at least two inches of potting soil below the bulbs. Try planting a mixture of both large and small bulbs. Layer the bulbs so that the large ones (tulips and daffodils) are planted deeper in the container and smaller ones (crocus, grape hyacinth, Scilla, etc.) are planted more shallowly. For example, white tulips planted with blue grape hyacinths make a classic color combination.    
  • Naturalizing bulbs – If you’ve got enough space in your lawn and the right growing conditions, try naturalizing bulbs. Basically, this means dedicating an area in your lawn or elsewhere where the bulbs may grow undisturbed.   In other words, do not mow the grass until the bulb foliage dies back. Before committing to this landscape project, make sure you can live with the tall grass for a couple of months. The easiest way to plant the area is to toss the bulbs in a random pattern and plant them where they fall. This is how they grow in nature rather than in straight rows or neat clusters. As the bulbs multiply, they will eventually fill in the area, creating a mass of blossoms in spring. Daffodils, crocus, grape hyacinths, and snowdrops are generally good choices for naturalizing. A word of caution:  Scilla siberica (commonly known as Siberian squill) and Hyacinthoides hispanica (also known as Spanish bluebell or wood hyacinth) are often used in naturalized settings but these bulbs spread aggressively and may be potentially invasive. So, monitor these and other naturalized bulbs to make sure they stay where you intended them to. These are all hardy bulbs that don’t require special treatment in order to thrive.

SOURCES

American Horticulture Society, A-Z Encyclopedia of Garden Plants (2008)

Bryan, John E., Bulbs (Revised edition 2002)

The American Daffodil Society, http://daffodilusa.org/

Virginia Cooperative Extension Publication 426-201, “Flowering Bulbs: Culture and Maintenance,” http://www.pubs.ext.vt.edu/426/426-201/426-201_pdf.pdf

Virginia Cooperative Extension Publication HORT-76NP, “Fooling Mother Nature: Forcing Flower Bulbs for Indoor Bloom,” http://www.pubs.ext.vt.edu/HORT/HORT-76/HORT-76.html

 

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