Documents: Special Interest: Seeds, Bulbs & Such:

Fall Season Bulb FAQs – The Classics
by Sally Ferguson
August 28, 2016

Why don't flower bulbs in the ground freeze in the winter?

Bulbs are designed by nature to withstand cold winter temperatures. Indeed they rely on winter's cold to trigger the biochemical process necessary to bring the bulb to flower in spring. While winter soil may actually freeze to depths beyond which the bulbs are planted, soil temperature will rarely fall below 29° F or 30° F (-1°C). At these just-below-freezing temperatures, water in the cells of the bulb may freeze but the cells will not be harmed. Also, as is true for many hardy plants, cold temperatures trigger starches in bulbs to break down into glucose and other small molecules. This simple sugar or glucose, interacting with other small molecules, acts in much the same way as salt on a winter sidewalk. The sugar in the bulb, like the salt on the sidewalk, lowers the temperature at which water freezes. This fortunate chemistry helps to keep bulbs safe and snug in their winter beds.

Other factors that help keep soil temperatures within tolerable limits include an insulating snow cover or a nice layer of mulch over the bulb bed once the ground temperatures have dropped.

How deep do I plant flower bulbs?

"Fall is the time to plant spring-blooming bulbs and it could hardly be easier, says Sally Ferguson, director of the Netherlands Flower Bulb Information Center in Danby, Vt. "Big bulbs including daffodils, tulips and hyacinths get planted 8 inches (20 cm) deep, small bulbs such as grape hyacinths, crocus and others are planted five inches (13 cm) deep. Plant in well-drained soil, cover up, water well and wait for spring. It's as simple as that."

I'm sick of deer and squirrels destroying my garden. Which spring-bloomers can I plant this fall and hope to enjoy next spring?

Colorful, delectable-looking tulips, daffodils, hyacinths, crocuses, alliums, grape hyacinths and other spring-flowering bulbs are prized in spring by people everywhere. But, animals, too, find some bulbs appealing. While animals don't much care what flowers look like, some find bulbs and bulb flowers incredibly tasty. In particular, troublesome deer, squirrels, voles and groundhogs will thank you for planting tulips or crocuses. Many other bulbs, such as daffodil and alliums, hold no appeal to furry foragers and are generally shunned because of their bitter taste.

If animal pests are a problem in your area, a first line of defense is to plant pest-resistant plant material in exposed garden beds or wide open spaces and put more vulnerable bulbs such as tulips and crocuses in protected areas, say by the front door or in fenced areas. Potting up and protecting these tastier bulbs is another option. Second line defenses include pest-proofing or -repellants such as netting, screening, dogs, sprays and other techniques. Of course, if deer are truly starving, they'll eat just about anything, including the bark off trees! Still, planting the less tasty bulbs in exposed sites will greatly improve a garden's overall survivability in problem areas.

Following is a "Quick List of Pest-Resistant Bulbs" from the Netherlands Flower Bulb Information Center in Danby, Vermont. All are ranked high on beauty and low on pest-appeal.

Allium, ornamental onion. Bloom late spring to early summer. Hardy in USDA zones 4-8, depending on variety. Camassia. Bloom late spring. Hardy in USDA zones 4-8.

Chionodoxa, glory of the snow. Bloom late winter, early spring. Hardy in USDA zones 4-8. Colchicum. Bloom late summer and fall. Hardy in USDA zones 4-8, depending on variety.

Crocus tommasinianus. Bloom late winter, early spring. Hardy in USDA zones 4-8.

Eranthis, winter aconite. Bloom late winter, early spring. Hardy in USDA zones 4-7.

Fritillaria. Bloom mid to late spring, depending on variety. Hardy in USDA zones 4-8.

Galanthus nivalis, snowdrop. Bloom late winter, early spring. Hardy in USDA zones 4-8.

Hyacinthoides hispanica, Spanish bluebell. Bloom late spring. Hardy in USDA zones 4-10.

Hyacinthus, hyacinth. Bloom mid-spring. Hardy in USDA zones 4-8.

Ipheion. Blooms early- to late-spring, depending on variety. Hardy in USDA zones 4-9.

Leucojum, snowflake. Bloom mid- to late-spring. Hardy in USDA zones 4- (There is also a fall-blooming

Leucojum autumnale, hardy in zones 5-9)

Muscari, grape hyacinth. Bloom mid- to late-spring, depending upon variety. Hardy in USDA zones 4-9.

Narcissus, daffodil. Bloom early- to late-spring, depending upon variety. Hardy in USDA zones 4-11, depending upon variety.

Ornithogalum. Bloom early to mid-spring. Hardy in USDA zones 5-8.

Oxalis. Bloom mid-spring to fall, depending on variety. Hardy in USDA zones 7-10, depending on variety.

Scilla. Bloom early spring, to early summer, depending upon variety. Hardy in USDA zones 4-10, depending upon variety.

Is it better to plant bulbs earlier or later in the fall?

As a general rule, earlier is better – as long as the soil temperature has cooled sufficiently. One way to gauge "the right time" is to wait until autumn night-time temperatures drop below 50° F (10° C) for two consecutive weeks. Once planted, bulbs need to establish strong root systems before the frosts of winter set in and the bulbs enter a new cycle in preparation for spring blooming. Planting six to eight weeks prior to hard frost is ideal, but bulbs manage to thrive with far less lead-time. Remember to plant bulbs in areas that drain well and water newly planted bulbs to help get those roots growing!

When is the optimal time to plant tulips, daffodils and most other bulbs in fall?

In most areas, the "window" of time for planting bulbs in fall is fairly wide. Here is a practical way to plan: Time to start planting bulbs: once night-time temperatures in your area drop into the low 50s ° or 40s° F (4-10° C) for two weeks.

Time to finish up: once hard frosts approach. Generally bulbs root best in the period six weeks or more prior to the ground freezing.

After planting bulbs: water the site well. Typically fall rains will take over this task for the balance of the season. For more information on fall planting see, Bulbs & Gardening.

It's smart to buy bulbs as soon as they are available in fall, otherwise varieties that you desire might sell out. But it's also smart to resist the temptation to plant them right away if local weather is still quite warm.

Fall-planted hardy bulbs are so easy to grow they're practically foolproof, but planting before the soil cools down can cause problems, especially if the autumn weather turns wet. Most fall bulbs, tulips especially, come from areas where the winters are very cold, but the summers are hot and dry. Bulbs planted in warm, wet soil are susceptible to rot, mildew and other woes.

Fall bulb planting should wait until soil temperatures drop to 55°F (12°C) or cooler. This normally occurs in the fall once the average nighttime temperatures drop to around 50°F (10°C) or lower for two weeks or more.

While waiting to plant, store the bulbs in a cool, dark place away from direct sunlight. After planting, in a well-drained spot, water the bulbs well. Fall rains normally then kick in, providing all the moisture necessary. This scenario will help bulbs establish strong, deep roots and give you healthy, happy flowers next spring.

Why can't I plant tulips in the Spring?

Spring-flowering bulbs such as tulips and daffodils must be planted in the fall to bloom in spring because they require a long period of cool temperatures to spark the biochemical process that causes them to flower. In fall, it's important to get them into the ground before the ground freezes. They need time to develop strong roots. Six to eight weeks of rooting is ideal, but if fall slips away and winter is close, plant your bulbs anyway. Bulbs are programmed by nature to survive. Even in less than optimal circumstances, bulbs tend to make the best of things.

Do tulips prefer a sunny or a shady spot in the yard?

Tulips thrive in sun or partial sun. But when planting your tulips this fall, don't be fooled by autumn's patterns of sun and shade! Remember that come spring, when tulips come up, all the deciduous, non-evergreen trees in your yard will be beautifully leafless. There's a lot of sun in a spring garden!

Is buying bulbs in bulk an option?

When planning fall bulb planting projects, remember that buying tulips, daffodils and other flower bulbs in bulk can greatly reduce prices per bulb. For example, the approximate cost of highly-desirable marigold-orange Tulip 'Ballerina' can vary from about 77 cents each (bought in bags of 10) to 31 cents each (for orders of 1,000). Following are tips on buying bulbs in bulk from the Netherlands Flower Bulb Information Center in Danby, Vt,.

Consider pooling bulb orders with friends or neighbors to achieve bulk quantities and save money. Make an occasion when the bulbs arrive by throwing a Bulb Divvying-Up Party. Look for naturalizing mixes. Many retailers offer naturalizing mixes of daffodils, crocus and other bulbs at very good prices as the bulbs are sold in large quantities for mass plantings and also can include less expensive smaller caliber bulbs which will mature in place once planted in the landscape.

Find out when local retailers typically hold their end-of-season sales. What seems late in the season to a retailer may seem just-right-for-planting to you.

For a list of mail-order bulb companies, visit

Is there a difference in bloom time between first year's bloom and later years'?

Yes there is. Established perennial or naturalized bulbs tend to bloom 10 days to two weeks earlier in subsequent years than they did their first year because they're more settled and have a longer fall period for rooting. This is especially important to think about in fall when you are selecting bulb combinations to bloom together in spring, particularly if you're adding bulbs to an existing planting. You don't want to base future estimated bloom times on bulbs' first year performances – or you'll find your combinations out of sync down the road. .

What if it's already early winter and I still haven't planted my bulbs?

When best plans fail and you still haven't planted your bulbs by early winter, the answer is – just plant the bulbs as soon as you can, even if you have to chip into the upper layer of soil. Bulbs are not dormant, they're alive – and they won't last much longer if left unplanted.

If you can get them into the ground (either in pots or in the garden), chances are good that they'll grow. If you don't plant them soon, you may as well toss them.

Bulbs that get less than 10 to 14 weeks (depending on their type) of sustained cold temperatures still come up but may be shorter than usual. If they are types or varieties that perennialize or naturalize, they'll come back normally in future years if their foliage is left to die back after bloom in spring.

Tip: if you know in advance you won't be able to plant until very late, throw small tarps or leaf piles over proposed planting areas to keep the soil warm and workable until you are ready to dig.

Expert gardeners have another late season trick up their sleeve: They pot up unplanted bulbs for indoor forcing, or as container plants. With containers, you have the advantage of being able to control the initial soil temperature by adding your own soil. Choose the light potting soil mixes sold at all garden retailers. Move small containers to an unheated garage, old refrigerator or other cool, yet protected place. In spring, use the potted bulbs as outdoor accent plants or bring them indoors to enjoy.

Remember these are last-ditch measures. Once the time for fall planting has arrived in your area, the sooner bulbs are safely in the ground, the better.

Why is mulch used in winter?

Spreading mulch over fall-planted flower bulbs is a good idea. However mulching isn't advised for the reasons commonly thought. "Most people we talk to think you mulch bulbs as soon as you plant to keep the soil warm so the bulbs won't freeze over winter," says Sally Ferguson, director of the Netherlands Flower Bulb Information Center in Danby, Vt. "Actually, mulch should be applied later, once the ground gets colder, to keep the soil temperature consistently cool over-winter. The goal is to minimize damage from frost heaves and help retain moisture in the soil through the winter." Ferguson advises that homeowners plant bulbs approximately six weeks before local hard frosts typically start but wait until the cold weather is upon them to mulch their bulb beds. "If you mulch too early, overly warm soil conditions can promote disease and mildew," she explained. "Also, premature mulching invites mice, voles and other unwanted critters to nest in your bulb beds – poor you – and lucky them to find such warm cozy dens for the winter!"

What's the secret to getting bulbs to "come back" year after year?

Give your bulbs a good start and a little bit of attention each year and you'll enjoy rich, colorful rewards, spring after spring. Following are tips on planting and perpetuating perennial flower bulbs from the Netherlands Flower Bulb Information Center in Danby, Vt.

Choose bulbs that perennialize well. Not all bulbs will return year after year. Look for bulbs marked "Good for Perennializing" or "Good for Naturalizing." Not long ago, an informal group of Dutch experts put together a list of top-performing naturalizing or perennializing bulbs for the U.S. Their picks were: Narcissus 'Salome', Narcissus 'Ice Follies', Tulipa 'Orange Emperor', Tulipa tarda, Crocus tommasinianus 'Ruby Giant', Crocus vernus 'Jeanne D'Arc', Camassia cusickii, Leucojum aestivum, Anemone blanda 'Blue Shades', and Scilla siberica. Note: Bulbs are called good perennializers if they will come back at least three years in the garden, under proper growing conditions. Bulbs are considered good naturalizers if they will come back and will also increase and multiply over the years, when planted where conditions are right. For a comprehensive list of these and other bulbs that perennialize well, visit

Plant in soil that drains well. The Dutch have a saying: "Bulbs don't like wet feet." Avoid planting bulbs in places where water collects, such as near downspouts or at the bottom of a hill. Standing water is bad for bulbs. In a garden bed, work organic matter like compost or peat into the soil. Be sure to work the soil down a few inches lower than you will actually place the bulbs, so the roots have room to grow.

Choose the right light. Most spring bulbs prefer full sun, though some can tolerate partial shade. Pay attention to the flowering time on the package or in the catalogue. If the variety you're planting blooms early, chances are the trees won't have leafed out yet. You may have more sunny spots than you think!

Pointy end up. Bulbs have a top and a bottom. The pointy end is generally the top. Of course with small bulbs, such as Anemone blanda, scilla and others, it's not always easy to tell. The other rule, not quite so catchy, is "basal plate down." The basal plate is the flat part on the bottom of the bulb from which the roots will sprout. Take a good look and it's not too hard to find this flat, usually darker basal plate. If you make a mistake, take heart. The bulbs will more than likely right themselves as they root. They really are that easy to grow! If in real doubt, plant the bulb on its side.

Perennialized bulbs need food. Bulbs that are planted for only one season of enjoyment don't need fertilizer. They already contain all the food they need to flower once. Naturalized and perennialized bulbs are another story. In spring, they need to recharge after blooming to prepare for the following year. For the first season: Work a good organic compost or well-rotted cow manure into the soil when planting and also "top-dress" or mulch with this material.

Or, add compost or peat to the soil for drainage and top-dress with a 9-9-6 NPK slow release or an 8-8-8 or 10-10-10 NPK fast-release soluble fertilizer (about one tablespoon per square foot). What you do next spring depends on what you did in the fall. If you used a slow release method, such as the cow manure or the slow-release NPK, don't do anything.

If you used a fast-release fertilizer, apply a nitrogen-rich fast-release NPK fertilizer in the spring just as the shoots first emerge from the soil (which would be about 6 weeks prior to bloom).

Each fall, fertilize again by your method of choice.

Deadhead flowers after spring-flowering bulbs have faded. "Dead-head" the plants by snipping off the faded flowers. This prevents the formation of seeds, but allows the green foliage to die back naturally, a process which generally takes about six weeks after bloom. A dead-heading exception: daffodils do not require dead-heading — though some people choose to do so for aesthetic reasons.

Large naturalized beds of daffodils can be left "au naturale" after blooming and suffer no ill effects. Let the foliage die back. The six week leaf die-back time is a critical "work period" for leaves busy with photosynthesis (the process by which leaves combine chlorophyll and sunshine into the starches that recharge the bulb with "food" for next year's bloom). Avoid the urge to "tidy up" bulb plantings after bloom by tying up the leaves with string or rubber bands, as some suggest . The leaves must be free to soak up sunshine during this crucial period. If dying foliage seems unattractive, the best solution is camouflage.

Interplant bulbs with hostas, coral bells (heuchera), lilies or other perennials that leaf out early in the spring season. They will grow up and around fading bulb plants and disguise the dying foliage of the bulbs.

Some bulbs don't perennialize well.

Remember that some bulbs, such as many tulips and hyacinths, do not always come back strongly in subsequent years. If the variety you planted wasn't a variety marked good for perennializing or naturalizing, and they are planted in a prime position in the garden, then it's probably best to treat them as annuals and compost or toss them after bloom, freeing up the space to plant new bulbs in the fall.

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