By: Bonnie L. Grant, Certified Urban Agriculturist
Plants propagate from many sources. Seeds are the most common way but they also reproduce through offsets, corms, rhizomes, tubers and bulbs. Bulbs are underground storage structures that carry both the genetic starting material for the plant but also a food supply to get it going. The different bulb types are more accurately called geophytes and encompass a wide range of plant types.
The true bulb is a layered structure filled with plant carbohydrates with a plant shoot in the core. It has a basal plate where roots grow, fleshy scales or layers, the outer skin, the shoot at the center flanked by developing bulbets. Common spring bulbs, like daffodils and tulips, are true bulbs.
There are two different types of bulbs which are in the true bulb category.
Tunicate bulbs all have the outer skin or tunic. This papery cover protects the interior scales where the food sources are stored. Tulips are a good example of this type of bulb.
Imbricate bulbs, like lilies, do not have the paper covering. This type of bulb must stay moist prior to planting.
Many underground storage structures are also called bulbs but they are not true bulbs. These include corms, tubers and rhizomes. Each of these is also filled with carbohydrate sugars to fuel plant growth and development.
Corms – Corms are similar in appearance to bulbs but are solid inside. Crocosmia grows from corms, which spread rapidly and easily, as do gladiolus, crocus and freesia.
Tubers – A tuber is a swollen stem with growth nodes or eyes. Daylilies and cyclamen are examples of tuber types of flower bulbs. Tubers are propagated by planting a piece of the tuber with several healthy eyes. There are exotic and urbane types of flower bulbs, with a variety suitable for nearly every gardening situation.
Tuberous roots – There are also tuberous roots, like tuberous begonia, which are thickened roots that hold food sources.
Rhizomes – Rhizomes are another of the bulb plant types. They are simply underground stems that also store plant food and can sprout new growth. Common plants having rhizomes are irises. You can see the rhizomes on old stands of iris, as the large roots get pushed up out of the soil. They are easy to pull apart and start new plants.
Bulbets/bulbils – There is another bulb-type structure called bulbet, or bulbil. These are the tiny round organs found growing on the tops of Alliums and related plants.
Not only flowering plants spring from bulbs and other storage structures. Potatoes come from tubers, bamboo arises from rhizomes and elephant ear plants have tuberous bulb-like structures. While not technically considered bulbs, hostas are also commonly grouped with other bulbous type plants.
The most well known, however, are the flowering types. The wide variety in types of flower bulbs speaks to nature’s wisdom in providing variety and adaptability in her plants.
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Read more about General Bulb Care
As a founding employee of Gardener's Supply, I wore many different hats over the years. Currently, I have my own company called Johnnie Brook Creative. The gardens around my home in Richmond, VT, include a large vegetable garden, seasonal greenhouse, cutting garden, perennial gardens, rock garden, shade garden, berry plantings, lots of container plants and a meadow garden. There's no place I'd rather be than in the garden.
Growing bulbs indoors lets you enjoy the colors and fragrance of spring when it's still months away. The key to success with indoor bulbs is to plan ahead. Many people don't realize that there are two types of bulbs for indoor growing: those you need to chill and those you don't.
In this tutorial, Scott Atkinson shows us how to identify different types of bulbs. Common types of bulbs are: tulip, daffodil and lily. These are most easily identified but there are many that appear in flowers. A core looks similar to a bulb but it is a solid tissue and doesn't have an leaves, just a hard core with a protective covering. There is also tubers which are what potatoes and other foods grow from. These cause eyes to form and create different types of things to grow. You will now be able to identify different types of bulbs when you are planting your garden and you can take care of them the best you can!
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Globe LED Bulb
Shaped like incandescent bulbs using LED (light emitting diode) technology instead of filaments, these bulbs are a great replacement for older ones in your home. They use a lot less energy than traditional incandescent bulbs and will greatly lower the cost of lighting for your home or business.
Twisted Fluorescent Lamp
These fluorescent light bulbs use a lot less energy than incandescent bulbs and will last for a very long time, resulting in large savings during the lifespan of these bulbs. They work well in both homes and businesses and have brighter or dimmer variations.
A filament is heated until it glows and produces the light in these bulbs. These are being phased out so that more energy-efficient bulbs will be produced instead, but they last about a year and don’t contain mercury. They also include the added benefit of having the capacity to be used with a dimmer switch, so you can easily control the brightness in a room.
Compact Fluorescent Lamp
These compact fluorescent light bulbs will last for thousands of hours and put off very little heat. Because of the way they are constructed and how they work, they do tend to cost more than incandescent lamp bulbs. However, they will use less energy over the period of their life.
These bulbs are very energy efficient, last for an incredibly long period of time, and produce high quality and bright light. They’re great for overhead lighting, outdoor lighting, and for use as spotlights in sports complexes or other places.
Tube Fluorescent Lamp
These bulbs are generally more expensive to buy than those that use a traditional incandescent bulb. However, since they have such a long lifespan, they tend to pay for themselves over time. They do provide a strong source of light, but you can’t dim them. Unfortunately, as they age, they may begin to flicker and will need to be replaced.
Flame Shaped Bulb
These bulbs are great for use in chandeliers or lamps that have the appearance of candlesticks. This bulb type creates a cozy light source and does well as accent lighting, due to the way they mimic actual flames due to their shape. Some can be dimmed, but others can’t, so it’s important to consider if you’ll need to dim the lights. The interesting shape and design adds a lot of complexity to your lighting.
LED lighting is energy-efficient and however this light bulb type is expensive to buy, but inexpensive to use. They put out very little heat, are rugged and difficult to break, and have a lower risk of starting a fire. You can’t always dim them, and sometimes they do not produce the same amount or quality of bright white light that incandescent bulbs do but if you’re looking for solid light output then an LED light bulb might be the best way to go.
Dimmer switches are a great way to have more control over the brightness in your home or office. They usually replace the light switch that you already have and can be quickly wired into the wall to give you instant control over the output of light in your home.
Fluorescent lighting might not be the most ambient, but it is surely one of the more effective. These bent light bulbs offer the same benefits as fluorescent bulbs or a fluorescent tube in your favorite lamp. They’re a very strong and reliable source of light and will keep your workspace nice and bright so that you can see clearly. Due to their unique shape, they can’t be used in every application but will work perfectly in the right lamps.
These strong bulbs are generally used in a spotlight by both homeowners and business owners. You can use them to brighten up the space where you work, or to provide accent lighting for rooms and outdoor fixtures.
These lights are ideal if you want constant light without the concern of flickering or accidental dimming. While they can be used in kitchens, they are most often used in offices, retail stores, and schools.
These bulbs use less energy than incandescent bulbs, but they are similar because they have a filament in them that is heated until it glows. They don’t contain any mercury and generally last about a year.
These bulbs are best for when you need very bright light but want to save money over traditional high wattage bulbs. They are ideal for outdoor lighting as well as for a shop or barn.
These bulbs work really for desk lamps, lighting under cabinets, and task lighting. They vary in lumens and how long they will last.
Adapters are the best way to help maximize how much lighting you can have in your home without having to install more lights. They are very safe to use and easy to wire and install. Both polarized and non-polarized versions are available for purchase.
Circular Fluorescent Lamp
These bulbs give off the brightness of fluorescent light in an even circular shape.
These bulbs come in high and low-pressure options. The high-pressure sodium bulbs produce light that is reddish-yellow in color, while low-pressure ones produce a more balanced white light. Sodium in an excited state creates the light in this bulb.
The silver surface on these bulbs works to direct light to a specific area. These are the best bulbs to use if you want to have spotlights installed in your home because they are designed to project light in one direction.
LED Strip Light
Not only will you save money by using LED technology, but you will also be able to enjoy plenty of direct light for the tasks that you are working on. They provide even light distribution thanks to the acrylic lens and can be used in a number of applications, such as parking garages, garden centers, and even loading docks.
Good question. The clue's in the name with this one really - spring bulbs flower in the spring, and summer bulbs flower in the summer.
You don't want to mix them up as, if you do, your bulbs may not flower at all as they'll be exposed to the wrong growing conditions.
Tom Clarke, head gardener at Exbury Gardens in the New Forest, shares that there's a common misconception that spring is the only time of the year to bloom bulbs in your garden. "There are some wonderful summer-flowering bulbs that you can plant, and there are some easy tricks to make sure you make the most of their scent and structure," he shares.
According to BBC TV gardener and landscape designer Mark Lane, when it comes to summer bulbs, there are many to choose from.
"Summer bulbs span tubers, corms and rhizomes. My top five are dahlias, lilies, eucomis, crocosmia and begonia," he shares.
Alongside those, there are also the lactiflora varieties of peony, agapanthus, gladioli, nerine for late summer and early autumn, as well as canna and Zantedeschia, he explains.
Tom's top bulb choices for scent are lilies and freesias for structure, alliums and agapanthus and for show-off blooms, gladioli and begonias, which are officially tubers, he adds.
A handy little list of summer bulbs:
The majority of summer bulbs are sun worshipers, so Mark recommends planting them in full sun. "If you're working with a shady garden, balcony or patio area, begonias will grow in partial shade, as will martagon lilies," he shares.
Other than that, the requirements will differ from bulb to bulb. Generally speaking, summer bulbs prefer warm and sunny.
Do make sure you're planting in free-draining soil too - you don't want any of your bulbs rotting.
You've learnt that spring bulbs bloom in spring, and summer bulbs in summer, but when should you plant them both?
"Whereas spring bulbs, such as crocus, narcissus, muscari and tulip, are planted in the autumn and flower in the spring, summer bulbs are planted in the spring once the soil is beginning to warm up," explains Mark.
If you find it hard to remember, think of this: summer bulbs come from hot climates, and therefore need a minimum of 13 degrees celsius to start to grow. "A great way of remembering? Summer bulbs get planted at the same time your tomatoes go outdoors," Mark explains.
Fun fact: you can actually plant the hardy summer flowering bulbs such as lilies and crocosmia in the autumn, shares Kate. "Less hardy varieties, such as gladiolis and begonias, must only be planted outside when all risk of frost has passed in late spring or, if you're keen to get going, they can be potted indoors in mid-spring and moved outside when the weather warms up," she explains.
When choosing pots, keep in mind that (a) spring-planted bulbs have a much longer growing season than fall-planted bulbs do and (b) some grow much larger. That means you can’t cram them in as tightly as you would fall-planted bulbs, so you need roomier pots. Some bulbs will also appreciate the cooling protection of a cache-pot. For guidance, see tips #2, #5, and our bulb-by-bulb advice below.
To avoid drowning your bulbs, especially those that will sit out in the rain, avoid pots without drain holes, and glazed or plastic saucers.
Potting soil usually works better in pots than garden soil because it holds more moisture and allows roots to penetrate and bulbs to expand more easily. Quality varies widely, though, so avoid bargain-priced brands, and choose a soil that’s relatively porous and fast-draining, with a good percentage of perlite, vermiculite, or bark.
Plant most spring-planted bulbs so they’re closer and shallower than they would be in the ground — but not as close and shallow as fall-planted bulbs in pots. The goal is to make the most of the limited space, but since spring-planted bulbs have to support top-growth all summer long instead of for just a few weeks in the spring, they need more room. This is especially true for dahlias and cannas because (a) they get so big and (b) if their growth slows or stops, so will their blooming. See our bulb-by-bulb tips below for guidance.
Like most gardeners, we enjoy combining all sorts of annuals in pots, but in our experience most bulbs do better when potted separately. That allows you to give each type the individualized care it needs to grow and bloom best, and as summer advances you can easily rearrange the pots and move those in full bloom into the spotlight.
The dry peat moss in potting soils can be difficult to wet thoroughly, so the first time you water your newly planted bulbs, let the pot stand in a saucer of water for up to an hour in order to soak up as much moisture as possible.
When bulbs are growing vigorously, pots can dry out quickly. Check the soil with your finger daily, and water as needed to keep it moist but not soggy. Early in the season when bulbs are just getting started and the weather is cool you’ll need to water less, but later when there’s a lot of top growth, the weather is hot, and roots have filled the pot so completely that there’s less soil left to hold moisture, you’ll need to water more — often daily, and sometimes even more!
To help give your bulbs more water when they need it, set a saucer under each pot and water until it’s at least partially filled. Be careful, though, especially when bulbs are just getting started or growth is slow, because constantly soggy soil will cause most bulbs to rot and die. The goal is to give them a reservoir to draw on for a few hours. If there’s still water in the saucer, say, eight hours later, dump it out and water less next time.
Plastic and glazed saucers hold water longer than unglazed terra cotta ones. That can be good or bad depending on the plants’ needs, so keep that in mind when using them.
If your pots are open to the rain, be sure to empty their saucers after every shower to avoid water-logged soil and root rot. This is even more of a danger with pots or cache-pots that lack drain holes, which is why we recommend you avoid them altogether.
Unlike their fall-planted cousins, spring-planted bulbs in pots need to be fertilized. Their growing season is long and their pots are small, so eventually they’ll exhaust the nutrition that’s in the potting soil and their growth and blooming will falter. To remedy this, wait until the plant is in full growth and then simply add a bit of liquid or water-soluble fertilizer to your watering can every few weeks. Although “all-purpose” fertilizers will work just fine, you might want to use something like Miracle-Gro Bloom Booster which has more phosphorus to promote flowering. Of course there are many good organic fertilizers available, too.
Whatever you do, remember that (a) big plants such as dahlias and cannas will need a lot more fertilizer than small plants such as rain lilies, and (b) too much fertilizer can be deadly, so use your green-thumb intuition and fertilize judiciously.
Most spring-planted bulbs need at least a half-day of full sun to grow and bloom well, and they’ll do better with more. This is especially true in the north where sunlight is never as strong as it is further south. Of course a spot that’s in full sun in mid-summer when the sun is high in the sky can fall into shade later in the season as the angle of the sun declines, so keep an eye on this and move your pots as needed.
Sunny spots can get very hot, though, which may cause problems for some bulbs. Soil in pots heats up much faster than soil in the ground, and if a pot is set on a deck or paving, or near a south or west wall, it will get even hotter and stay warm longer. In cooler parts of the country, some bulbs such as tuberoses, rain lilies, and crinums will appreciate the extra heat, but glads and especially dahlias won’t.
To keep soil cooler, double-pot your bulbs by planting them in one pot — say a common black-plastic nursery pot — and then slipping that inside a decorative cache-pot. The outer pot will shade the inner pot, and the air space between the two will slow the transfer of heat. Just make sure the cache-pots have drainage holes, to avoid drowning your bulbs.
Another way to cool pots is to raise them even slightly off the deck, terrace, or other hard surface they’re sitting on. Wood, concrete, stone, and brick can all get very hot when the sun is beating down on them, and they’ll hold the heat long after the sun is gone. Although some bulbs will thrive with the extra heat, others will struggle — so see our bulb-by-bulb tips below. To cool pots, raise them (or their saucers) off the deck or paving by setting them on a few small sticks or rocks. Even a ¼-inch air space will help reduce the heat transfer. You can raise pots higher by setting them on overturned pots and other pedestals, but even then providing a bit of air space between the pot (or its saucer) and whatever you set it on will help keep it cooler.
Finally, avoid too much heat by keeping pots away from south and west walls where the sun’s direct rays can create oven-like conditions.
Don’t restrict your pots to the porch, deck, or patio. They make great accents and focal points out in the garden, too, and visually link garden and house. Since they’re so portable, it’s easy to switch pots around so the ones in full bloom are always in prime spots, and when a pot of tuberoses starts to bloom you can set it wherever you’ll most appreciate its evening fragrance — maybe even under your bedroom window.
Another great way to enjoy pots of bulbs such as glads or tuberoses in the garden is to plant them in black plastic nursery pots, grow them in an out of the way spot like your vegetable garden or back of the border, and then when they start blooming move them wherever you need some excitement. There’s usually no need to bury the pots. Just set them on top of the soil where the foliage of other plants will mask them from view — and don’t forget to water them whenever you water your other pots.
Most spring-planted bulbs aren’t winter-hardy in much of the country, which is why they’re planted in spring instead of fall. And even if they ARE hardy in your zone, that means they’re hardy when grown in the ground — where the earth protects them like a huge insulating blanket — not in pots above ground where temperatures can be as much as 20 degrees colder, the equivalent of two full hardiness zones.
As winter approaches it’s perfectly fine to dump your bulbs out of their pots and compost them, just as you would fuchsias, tomatoes, or any other plants that aren’t hardy in your zone.
If you want to, though, it’s easy to store most spring-planted bulbs indoors during the winter. For example, here in zone 6a we keep our pots of rain lilies growing outside as long as possible in the fall, making sure they get as much sunlight as possible as the waning sun sinks lower in the sky. When the first frost threatens, we move them to a warm spot overnight and then back into the sun in the morning when it warms up again. Weeks later when the weather gets so cold that we’re doing this almost every night, we simply move the pots to a dim, cool, well-ventilated spot on our basement floor and stop watering them completely so the foliage will wither and the bulbs go dormant. Then we put a note in our phone to start checking on them in early spring for the first signs of new growth.
Once green sprouts start to emerge — which is often much earlier than you’d expect — you’ll probably want to move the pot into the sunniest spot you can find and start watering it lightly. However, if warm weather is still a long way off, we often delay that for a couple of weeks and the bulbs seem to cope. The sooner you can get the pots outside in full sun, the stronger the foliage will be, but remember these are tender bulbs and they can’t take as much cold as hardy bulbs such as daffodils. When you start putting them outside, harden them off gradually as you would seedlings you’ve started inside. Leave them for just an hour or two at first, in a sunny spot that’s sheltered from the wind, and then gradually extend their time outdoors a little more every day, giving the foliage a chance to toughen up and adjust to life outside.
Of course you can also empty your pots in the fall and store the bulbs in mesh bags, plastic tubs, etc. See our “care” links below for easy instructions. But remember — composting is also a perfectly honorable choice!
No matter how big of a pot we put them in, cannas never get as big or bloom as much as when we plant in the ground, so be prepared for that. They like heat, so they often do better on decks and paving where it may get too hot for other bulbs. They’ll want a lot of water once they get going, so keep their saucers filled. They’re big plants and the more stalks they produce, the more they’ll bloom, so fertilize regularly. Be careful, though, because if their rhizomes multiply to the point where they fill the pot, they can break it. To learn more, see our complete info on canna care.
We grow our crinums in pots, and we love them, but they’re more of a challenge in pots than most spring-planted bulbs are. They’re big bulbs — some will grow to football size over time — and their thick, permanent roots can quickly fill a pot completely. That makes watering difficult and may eventually break the pot. To learn more, read the advice of two of our northern customers, and see our info on crinum care.
Crocosmia are slender-growing and combine well in pots with other plants, although they’re also striking when grown alone. Give them plenty of sun and water. To learn more, see our complete info on crocosmia care.
Dahlias grow big, so give them as much room as possible, and plenty of water and fertilizer once they get going. To bloom well, they need lots of sun but even more importantly they need to be cool at night, so see our advice in tip #5 above. Don’t forget you’ll need to stake most of them (although short ‘Lutt Wichen’ and ‘Madame Stappers’ need little or no support). In winter, you can store them right in their pots in a cool, dry spot. To learn more, see our complete info on dahlia care.
Daylilies are hardy perennials that need an extended cold period every winter, which means you can’t store them inside. We don’t encourage growing them in pots, but if you want to try it, follow and adapt our advice for FALL-planted bulbs, above.
We often plant glads in black plastic nursery pots and then when they bloom we set them into the garden wherever a splash of color is needed. As a bonus, the rigid sides of pots help keep glads standing upright better than they often do when planted in the ground. To learn more, see our complete info on gladiolus care.
We don’t recommend growing iris in pots, but if you want to give it a try, follow and adapt our advice for FALL-planted bulbs, above. (And please let us know how they do!)
Rain lilies are great in pots, and were once commonly grown that way, even in the North. For us they seem to do best in pots that are shorter than they are wide, such as those sold as “azalea pots” or “bulb pots.” Plant the small bulbs close together — 50 in a 10-inch pot isn’t too many — and once they get going, water and fertilize them regularly. Bloom may be modest the first year as the bulbs settle in, but with good care they will bulk up and give you more flowers every year. Keep them growing outside as long as possible in the fall — a bit of cold weather may increase future bloom — and then store dry and cool indoors through the winter.
To learn more, read one Wisconsin gardener’s inspiring 100-year-long success story with pink rain lilies — which “thrive on neglect,” she says — and see our advice on rain lily care.
Richly fragrant tuberoses are our #1 favorite bulb for pots. In the North, we always recommend growing them that way, so you can give them maximum heat and sun. In winter, simply store the pots dry inside in a cool spot. When spring returns, bring them back outside, water and fertilize regularly, and they’ll bloom again. After their second summer, though, the rhizomes will have become so crowded that you’ll need to repot them. To learn more, see our complete info on tuberose care.