Growing Bulbs
This page contains information about growing and storing bulbs, corms, rhizomes, and tubers of all kinds. The focus is on gardens in zone 6, but much of this information will be useful to bulb growers everywhere. Information and links are continuously being added so come back often.
Planting Flower Bulbs
Fertilizing Bulbs
Pest-Resistant Bulbs
About Tender Bulbs
Overwintering Tender Bulbs
Favorite Spring-Blooming Small Bulbs (Chionodoxa and Ipheion uniflorum)
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.
Fertilizing Bulbs
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.
Pest-Resistant Bulbs
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
For information on canna, dahlia, gladioli, freesia, and crocosmia, see the September issue of In the Garden.
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.
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.