How to Plant and Grow Bulbs
This page contains information about growing and storing bulbs, corms, rhizomes, and tubers of all kinds. While the specifics of growing bulbs differs across regions, much of the information presented here will be useful to bulb growers everywhere. Information and links are continuously being added so come back often.
Topics covered include the following:
Selecting Flower Bulbs
Bulbs generally fall into one of two categories – spring-blooming (or hardy) bulbs and summer-blooming (or tender) bulbs.
Spring-blooming bulbs are planted in the fall, overwinter under ground, and bloom in the spring. In order to bloom, they need to a cold period during the winter, so not all spring-blooming bulbs will bloom in the warmer parts of the country. Spring-blooming bulbs include well-known favorites, such as tulips, daffodils, crocuses, and grape hyacinths, as well as lesser-known bulbs, including some of my favorite smaller ones.
Summer-blooming or tender bulbs cannot survive winter in the ground in colder regions of the country. They are generally planted in the spring after the last hard frost and are dug up and stored in a cool place in the fall. For information on storing tender bulbs, click here.
When selecting spring-blooming bulbs, aim for a wide range of flowering times. Most bulbs indicate on the packaging whether they are early, mid-, or late-season bloomers. By including bulbs that flower during each of these timeframes, you can have continuous blooms in your garden for up to three months!
Early Spring (weeks 1-4)
Snowdrop (Galanthus nivalis)
Winter Aconite (Eranthis hyemalis)
Danford Iris (Iris danfordiae)
Crocus (Crocus spp.)
Glory-of-the-Snow (Chionodoxa luciliae)
Siberian Squill (Scilla siberica)
Striped Squill (Puschkinia scilloides)
Grecian Windflower (Anemone blanda)
Common Grape Hyacinth (Muscari botryoides)
Early Daffodils (Narcissus spp.)
Netted Iris (Iris reticulata)
Midspring (weeks 4-8)
Checkered Lily (Fritillaria meleagris)
Species Tulips (Tulipa spp.)
Early Tulips (Tulipa spp.)
Early Alliums (Allium spp.)
Hyacinths (Hyacinthus orientalis)
Summer Snowflake (Leucojum aestivum)
Medium-Cupped Daffodils (Narcissus spp.)
Late Spring (weeks 8-12)
Dutch Hybrid Iris (Iris hybrids)
Midseason Tulips (Tulipa spp.)
Late Daffodils (Narcissus spp.)
Late Tulips (Tulipa spp.)
Alliums (Allium spp.)
Choosing a High Quality Bulb
There are two things to look for when buying bulbs: size and firmness.
Bulb Size – The larger the bulb, the larger the plant and flower. You’ll generally find that bulb prices correspond to size – so, for example, a larger daffodil bulb will cost more than a smaller one.
Choose a bulb size that makes sense for you. If you’re planting a large area that will naturalize over time, you may want to consider smaller bulbs that can grow after planting. These are sometimes referred to a “landscaper” or “contractor” sized bulbs and will often cost a little less (which is ideal if you’re planting a lot of them). However, if you plan to plant a smaller number of bulbs and want them to make a big impact, then larger bulbs would be a better choice.
Also, be aware that newer introductions and bulbs that are relatively rare or difficult to propagate will cost more. For example, some of the ornamental onions (Allium) can cost over $10 per bulb!
Firmness – You want to choose bulbs that are firm and free of soft spots or visible rot. Also check for signs of disease, cracking, or indications that the roots (on the flat end of the bulb) have been seriously damaged. All of these problems are likely to cause your bulbs to rot in the ground.
I generally recommend buying bulbs online from reputable dealers (see the list of recommended vendors at the top of the sidebar to the right). You’ll have a wider choice of bulbs and they’re generally larger that the ones bought at home improvement stores, or even your local nursery or garden center. However, if you want to buy locally, I strongly recommend supporting your local nursery or garden center as they will typically have good quality bulbs and can often order something for you if it’s not in stock.
Buy bulbs that grow well in your location—don’t be tempted into buying bulbs that are best suited for the humid south or bone-dry west if you live in the northeast.
Buy in large quantities. Most bulbs look best when planted in large masses. One or two bulbs here and there won’t have any impact in your landscape.
Planting Flower Bulbs
Planting flower bulbs is easy and will reward you with a beautiful spring show – if you do it right… Just follow these two basic rules to planting flower bulbs.
Plant Bulbs with the Pointed End Up – All bulbs have a “pointy end”, although it may not always be obvious. If you cannot tell which end is pointed, look for a flatter area where the roots are or have been – this is the bottom of the bulb. If still in doubt, just take a guess and plant the bulb. It will still grow, even if it’s upside-down, although the plant will be unnecessarily stressed and may eventually die if left upside-down. You can always dig up the bulb after it has finished flowering to see which side the leaves have emerged from (that’s the top of the bulb).
Plant Bulbs 2 – 2½ Times Deeper Than the Bulb Height – As a general rule of thumb, plant the bulb 2 – 2½ times deeper than the size of the bulb (measured from top to bottom). So if your bulb is a small 1 inch bulb (like a crocus), you would plant the bulb 2 to 2½ inches deep. If your bulb is a larger 3 inch bulb (like a daffodil), plant the bulb 6 to 7½ inches deep.
And that’s generally all there is to it. But if you want more details, read on…
In most locations, September is the perfect time to select your spring blooming bulbs. Most bulbs that bloom in the spring (e.g., tulips, daffodils, crocus, snowdrops) need to be chilled in order to bloom well. Here in southern Connecticut, plant bulbs in October and you’ll be rewarded with a colorful display starting in March.
Pointers for Planting Bulbs
- Don’t make the common mistake of planting tulips or daffodils in a straight line. Not only does it look un-natural, the flowers are often lost against the background and any bulbs that don’t emerge in spring will make a very noticeable hole in the display.
- Before planting, consider the light requirements of the bulbs and place them accordingly. Keep in mind that some bulbs will bloom before shrubs and trees leaf out.
- Plant small bulbs, such as muscari, squill, chionodoxa, winter aconite, and ipheon, in large drifts and allow them to naturalize.
- Consider some of the less common bulbs, such as the ornamental onions (I love drumstick allium), camassia, and small species tulips. Their flowers always evoke a “Wow, what’s that?!” from passers-by.
- Follow planting instructions that come with the bulbs. Some bulbs need to be planted deeper than others. As a general rule of thumb, the planting depth should be 2 to 3 times the height of the bulb (measured from the bottom of the bulb).
- Bulbs need well draining soil (they will tend to rot in clay). If necessary, amend the soil with compost before planting.
- Fertilize with a soluble 10-10-10 fertilizer (or bulb fertilizer) or incorporate superphosphate into the soil when you plant to encourage root growth.
- Do not add bonemeal or any type of bloodmeal to the planting hole. Those meals can lure animals to dig up the bulbs.
- If squirrels, voles, or other animals insist on digging up your bulbs, plant the bulbs in cages or surround them with chicken wire. The foliage will grow right through it but the animals won’t be able to feast on your tender bulbs.
- Water the bulbs well right after planting. They need to grow roots before the ground freezes solid. But don’t overwater or the bulbs will rot.
And if you’re looking for a good tool for planting bulbs, look no further than the Joseph Bentley long-handled bulb planter that we reviewed a while back.
Many gardeners assume that because hardy bulbs come back year after year that they need no special attention. While bulbs can survive for years without fertilizer, they thrive when given this little bit of extra attention.
Fertilize Bulbs When Planting – To encourage flowering in spring, add some bulb food to the planting hole before putting your bulb in. Just make sure that there is a thin layer of dirt between the bulb and the fertilizer, so that the bulb does not get fertilizer burn.
Fertilize Bulbs When Established – Fertilize bulbs twice a year for best results – once at the beginning of spring, before the plant flowers, and again in fall, after the first frost has hit your area. Fertilizing in spring helps bulbs start to store up food for over-wintering, while fertilizing in fall helps bulbs produce better flowers in the spring.
Chemical Bulb Fertilizers – Specialized bulb fertilizers can be expensive and aren’t really necessary. The key is to choose a chemical fertilizer in which the phosphorus (P) number is the highest (e.g., 5-10-5). Phosphorus is used by bulbs to grow and multiply, as well as to produce bigger and more vibrant flowers. Other important nutrients include nitrogen (N) and potash (K). Nitrogen helps bulbs put out healthy foliage, which in turn helps them to collect more energy from the sun. Potash will help the bulb fend of disease and live longer.
Natural Bulb Fertilizers – For gardeners who prefer to use only natural materials, compost will work well as general fertilizer (and soil conditioner). However, to ensure that there is enough phosphorus available to the bulbs, you may want to consider adding some bone meal to your compost.
Garden pests, especially deer, are a real problem for gardeners in many areas of the country. It’s a constant struggle to find plants that the deer won’t eat but that are also beautiful and/or fragrant. Fall can be especially difficult, as gardeners know that planting tulips and crocuses is simply going to a lot of effort to provide deer with a tasty spring treat. But there are some bulbs that deer generally won’t eat because of the bitter taste (unless they’re starving, in which case they’ll eat just about anything) – planting these pest-resistant bulbs can give you a beautiful spring display without attracting every deer in the neighborhood.
Below is a list of pest-resistant bulbs from the Netherlands Flower Bulb Information Center in New York City. All are ranked high on beauty and low on pest-appeal. All are hardy in USDA zones 4 – 8, depending on variety.
- Allium, ornamental onion. Blooms late spring to early summer.
- Camassia. Blooms late spring.
- Chionodoxa.glory of the snow. Blooms late winter, early spring.
- Colchicum. Blooms late summer and fall.
- Crocus tommasinianus. Blooms late winter, early spring.
- Eranthis, winter aconite. Blooms late winter, early spring.
- Fritillaria. Blooms mid to late spring, depending on variety.
- Galanthus nivalis, snowdrop. Blooms late winter, early spring.
- Hyacinthoides hispanica, Spanish bluebell. Blooms late spring.
- Hyacinthus, hyacinth. Blooms mid-spring.
- Ipheion. Blooms early- to late-spring, depending on variety.
- Leucojum, snowflake. Blooms mid- to late-spring.
- Muscari, graph hyacinth. Blooms mid- to late-spring, depending upon variety.
- Narcissus, daffodil. Blooms early- to late-spring, depending upon variety.
- Ornithogalum. Blooms early to mid-spring.
- Scilla. Blooms early spring, to early summer, depending upon variety.
About Tender Bulbs
Tips on Storing Tender Bulbs – A good way to store bulbs and corms is to fill old nylon stockings with peat moss, vermiculite or perlite, place the corms in the stockings, and hang them up on a clothesline or a hook. This procedure allows for good air circulation.
Keeping Overwintering Tender Bulbs Cool – If you don’t have a garage or other suitable outdoor location in which to keep bulbs cool, you can still keep them cool in your unfinished basement. Place the bulbs in a box lined with plastic and cover it with another sheet of plastic. Tilt the box towards an outer wall of your basement, with the plastic ‘top’ against the concrete wall. This procedure will generally give you a cooler temperature in the box than in the rest of your basement.
How to Overwinter Tender Bulbs
While gardeners in zones 8 and above can grow tender bulbs, corms, rhizomes and tubers year round, in other regions we need to dig and store these plants to overwinter them. There are no hard-and-fast rules for overwintering tender plants but here are some general tips:
- Use a pitchfork to lift the plants – it’s less likely to damage them.
- Keep the stored bulbs dry and cool – about 50F is cool enough to keep them dormant.
- Don’t store in air tight containers that could cause moisture, rot, or fungus to build up.
- Check regularly for desiccation and mold.
- Don’t forget to label by type and color.
Alocasia (Elephant’s Ear) – Most people treat these as potted houseplants and simply move them indoors and outdoors as weather allows. But if you grow them in the ground, lift and pot them before frost. Alocasia tubers can also be cleaned and stored in peat moss, in a cool, dry spot. Plants tend to get larger as the tubers age. Repot in early spring.
Begonias, Tuberous – Allow a light frost to kill the tops, but dig up the tubers before a hard frost freezes them. Cut back the foliage to about 6 inches and let the tubers dry for at least one week. Remove excess soil and foliage and store in peat moss, sawdust, perlite or vermiculiate at 50 degrees F. Repot in early spring and keep warm (68 – 75 degrees F). Move to a sunny spot when shoots appear. Keep evenly moist, but not wet. Plant outside after all danger of frost. NOTE: Begonia tubers must be started indoors in late January or February for summer flowers.
Caladium – Lift caladium plants before frost and allow them to dry in a warm spot. Cut back the foliage after it dies. Caldium bulbs don’t like to be stored in cold temperatures. Keep at 50 – 60 degrees F. Pack loosely in peat moss. Repot in early spring, about 2 inches deep, knobby side up. Keep the soil moist and warm (about 75 – 80 degres F). Move or plant outdoors after all danger of frost.
Canna—Allow frost to kill the tops, but don’t allow the rhizomes to freeze. Carefully lift the plants and cut off the dead tops. Hose off excess soil and allow to dry.
Rhizomes can be wrapped in newspaper and stored in paper bags or cardboard boxes, at 45 to 50 degrees F.
Cannas can be divided by hand. Simply break the rhizomes apart, insuring there are at least 3 eyes per division. Repot in early spring or plant directly in the garden once the temperatures remain above 70 degrees F.
Colocasia esculenta (Taro) – Like Alocasia, Colocasia can be brought indoors as a houseplant or dug and overwintered as a tuber. Store the dried tubers in peat moss. Check the tubers monthly and cut away any soft spots that may develop. Allow the remaining healthy portion to dry before restoring in peat. Colocasia can be repotted about 8 weeks before the last expected spring frost. If dividing, be sure each tuber piece has an eye. Allow the tubers to dry a few days before replanting them.
Crocosmia, Freesia, and Gladioli—Tubers are usually brought inside in mid-fall. Lift the plantswhen they yellow or after thefirst frost, allowing some soil to cling to them. Cut the stems back to 1 inch and allow corms to dry thoroughly for a couple of weeks. At this point, the remaining soil on the tubers should break away easily. Remove any old, shriveled portions, keeping only the new plump corms.
Once the corms have dried thoroughly, some people choose to dust them with a fungicide before storing them.
Store corms in peat moss, vermiculite or perlite at temperatures of 40–50° F.
In spring, plant the corms directly in the ground when the ground warms. Stagger plantings to extend the season of bloom.
Dahlia—Because these tubers don’t store very well, it is best to wait until the beginning of November (late fall) before bringing them inside.
Dahlias can be over-wintered in the ground as far north as zone 6 with sufficient mulch, but it’s risky. If you can, it’s better to lift them at the end of the season.
At the first light frost, cut back foliage to about 6 inches (or allow it to die back) and then leave the plant in the ground for a week or so (dig up the dahlia tubers if a hard freeze is predicted – don’t let them freeze in the ground). It’s easiest to see the dahlia eyes, for division purposes, about a week after the tops are cut or killed back.
Overwinter in peat moss at 50F to prevent premature sprouting and/or rotting. These tubers don’t like to get completely dried out. Check monthly for dehydration and mist lightly, if necessary.
In the spring, dahlia tubers are usually direct planted in the garden, once temperatures warm.