Forcing bulbs is a sure way to raise your winter spirits, especially if you live in the colder Northern climates. There’s nothing like the cheery nodding of daffodils or planting tulip bulbs in a container to chase away the winter blues and bring a light to your eyes.
For the new gardener, the process of growing bulbs indoors and coaxing them into bloom is called “forcing bulbs”. Forcing bulbs in containers is easy, but you have to think ahead if you are aiming for a beautiful display of spring bulbs during the late winter season.
September/October is the ideal time to pot up your spring bulbs if you want them to bloom 3-4 months ahead of schedule. Your choice of bulbs will have a lot to do with your success in this area, so choose carefully, especially if you are new to forcing bulbs. Check the catalogs or ask your nursery vendor which varieties are preferred when you are forcing bulbs.
When forcing bulbs it is best to plant only one single variety per pot. The reason you usually see only one color in a pot of forced bulbs is because even in the same species, different colors are apt to bloom at different times. When you are forcing bulbs, you want to see a container with a mass of color. This can happen only if you plant a single variety per pot. If you plant several varieties per pot, or even several colors of the same variety, your display is apt to be spotty and unattractive. If you want many colors, it is better to plant several pots of different colors. When the containers bloom, you can move them around to get the mass of color you are looking for. As the blooms in one container fade, you can remove it and give the next colorful bloomer the spotlight.
Planting Your Bulbs
Choose a bulb container for your planting. There is a commercial pot for bulbs that is about 4″ deep and 10 -12″ wide. This allows for root growth and many bulbs to be planted in one pot. Cover the drainage hole with screening or a coffee filter. Add a bottom layer of planter mix. A good recipe for bulb potting mix contains equal parts of soil, sphagnum moss, and perlite or vermiculite. If you prefer not to mix your own mixture, commercial “soil-less” potting mixes can also work well. Having large amounts of organic matter in your potting soil is not recommended as this could encourage disease and rot in your bulbs.
The mix should be deep enough so that the tops of the bulbs will be about 1″ below the rim when planted. Plant the bulb with the flat end facing down and the tip facing up. Place the bulbs shoulder to shoulder in the pot with about 1/4″ spacing between them. The bulbs are planted in the top of the pot to allow room for root growth.
When you plant large bulbs such as tulips and hyacinths, cover the tops with 1/2″ of soil. With daffodils, don’t try to cover their necks, only the fattened portions of the top of the bulb. Cover the smaller bulbs like crocus with 1/2″ of soil.
Once the bulbs are in place, cover them with more potting mixture. Label each pot with the type of bulb and variety. If they are going to go into cold storage at this time, water them thoroughly by setting the container in a pail of water and letting it soak until the surface of the soil is moist. The planting is ready for cold storage and you are now starting the process of forcing bulbs.
You Need Cold Storage When Forcing Bulbs
Bulbs need cold to bloom. Bulbs already have the flower inside them. It takes 12 – 14 weeks of cold treatment, (temperatures between 40-55 degrees) before a bulb will flower. This cold period gives the bulbs the time they need to develop a strong root system. Set your pots in an area that is cold and dark, such as an unheated cellar or garage. An old refrigerator in the garage set to that temperature is ideal. If you live in an area of moderate cold, it’s alright to store your bulbs outside in a protected box. Cover them with peat moss, styrene pellets, or other protective covering. Just be sure your bulbs are never exposed to freezing temperatures. During this period, roots require moisture for growth. Be sure to check your bulbs and keep the soil moist (not wet) during the period of cold storage when forcing bulbs.
At the end of the cold storage phase, when the sprouts are 2-5″ high and the roots can be seen from the drainage holes, place the containers in a cool 60 degree room. After a week or two in this intermediate room, they are ready to be brought into the house at normal room temperature. Be sure to give them adequate light at this point, or the plants will become leggy.
How to Extend Your Bloom Season into Spring
If you stagger your plantings when forcing bulbs, you can extend your blooming season way into spring. This takes a little more thought, but if you enjoy bringing spring early to counteract the long winter, try this method of forcing bulbs for a long blooming season indoors:
Pot up three containers at a time. They don’t all have to be the same bulb planting. For instance, you could try planting tulip bulbs in one pot, daffodils in another, and a hyacinth bulb in the third pot. Or if you prefer, you could try planting tulip bulbs in all pots, but each one a different color. Place them in storage, and two weeks later repeat the process. Do this several times and you will have a gorgeous display of bulbs throughout late winter into early spring.
If you don’t want to be constantly planting bulbs in containers, plant all you containers at once but keep them dry. Label your pots with the type of bulb and date you want to move them into cold storage. When you are ready to start forcing bulbs, water the containers thoroughly as mentioned above and move them into cold storage.
Forcing Hyacinths in Water
Another way to consider forcing bulbs is to do this in water. Both hyacinths and paperwhites can be forced in water. The important thing to remember in both instances is that bulbs will rot when sitting in water, therefore be very careful when using this process to keep the bulbs above water.
To force hyacinths on water, set a bulb just above(but not touching)the water in a forcing vase or other container. Special hyacinth forcing vases are available in nurseries and florist shops. Place the bulb in cold storage as described above. The process of forcing hyacinths in water is the same as described above. The only difference is that you must check the water. If it gets cloudy or foggy, change the water. When the roots are long enough, after about 10-14 weeks, bring it out of cold store and follow the procedures listed above.
You can also try this procedure that many people have had success using:
Store bulbs of an easy to force hyacinth variety (check the catalog or with your nursery vendor) dry in a paper bag in your refrigerator for 8-10 weeks. Then put them on water as for regular forcing (see above), anywhere in indirect light. As they grow roots and leaves, give them more light but avoid direct sun. Experiment with this system and see if it works with the bulb variety you have chosen as it’s a much easier way to force hyacinths in water as you don’t have to remember to keep checking the water.
Forcing Paperwhites in Water
Paperwhites are also forced in water. These are very easy to grow because they don’t need cold storage to bloom. Follow this procedure for forcing paperwhites:
Choose a container that is about 4″ deep and around 10″ wide that has no drainage holes. Spread 2″ of stones, marbles, colored glass pebbles etc, on the bottom of the container. Place your paperwhite bulbs, pointed tips up, on this layer. Place them as close together as possible for an amazing flowering display. Add a second layer of stones, glass, etc., up to the shoulders (the fattest part of the bulbs) of the bulbs. The tips should still be showing.
Add water up to the base of the bulbs. Don’t cover the bulbs as this will cause the bulbs to rot. Keep the bulbs in an area heated to about 60-65 degrees. The bulbs don’t need light while the roots are developing. Keep an eye on your bulbs and add water as needed. When roots have developed, move your paperwhites to a sunny area. They prefer really bright and sunny light at this point, but don’t like a lot of heat. If they get too warm, your plants will become leggy. Once your plants flower, move them to a cool spot with indirect light.
As with other forcing bulbs, you can extend the paperwhite season, by starting more pots several weeks apart.
After the Flowers Fade
Keep your plants in good health by providing water and sunlight. Once the danger of frost has passed, move the pots outside to an inconspicuous place where the foliage can continue to mature. Do not cut back the foliage as this is where the bulb gets it’s food for next year’s bloom. Once the foliage has died, plant them in the ground for continuous growth for years to come. Some people force the bulbs a second time, but the bloom is never as satisfactory as the first time around.
Discard hyacinths and paperwhites forced in water as they seldom bloom again
Keep a Garden Journal
If you’ve decided this is a process that really interests you, be sure to keep a journal of your progress. This can be a simple notebook recording the name of the bulb, date planted, date put into cold storage, and date of bloom. If you want more meticulous records, keep more details such as length of bloom time, how many bulbs in a pot, species of bulb, area of storage, etc.
In this way, from year to year, you can improve on your indoor display when forcing bulbs. You will be able to extend your bloom time, control flowering schedules, and tailor your display from year to year to fit into your desired schedule and display area. Before you know it, you’ll have all your friends and neighbors oohing and aahing over your skill as an indoor gardener.