Choosing Bulbs to Force
- The best bulbs for forcing are large, early-blooming bulbs.
- Hyacinths are the most reliable, narcissi are popular, and crocus are nice and small. But don’t limit yourself to these, there are many more to choose.
- Make sure you choose bulbs that are firm and a good size. Also make sure they are recommended for indoor cultivation and forcing.
- shallow plastic or clay containers are best, Bonsai pots are perfect. Make sure the container is twice the depth of your bulb to provide room for root development.
- Choose a pot with drainage holes if forcing is to take place in the open garden.
- Use indoor potting soil to stabilize the bulbs while they are growing.
- Start with a layer of moist soil in the bottom of the container. Place bulbs on this base with tips facing upwards. Make sure the tips are below the rim of the container.
- For the best display, set the bulbs close together but not touching each other or the sides of the container.
- Fill the soil in around the bulbs, pressing firmly but gently. The necks of hyacinths, narcissus and daffodils should protrude above the soil level, but all others can be covered. Water well, so the growing medium is damp.
- The bulbs now need a cold, but frost-free period in the dark. Place containers in a shady part of the garden. Cover with 15cm (6”) of peat, light soil, leaves or sawdust. If you live in a very cold region, or if you have no outdoor area, keep containers in a crawl space, garage or a dark, cool place. The ideal temperature for chilling bulbs is between just above freezing and 5°C (41°F). Make sure the temperature does not exceed 9°C (48°F) during the cold period, as this will make your bulbs think it’s time to grow.
- If you don’t have an outdoor area or cold covered space, you can put bulbs in the refrigerator. Just make sure to protect them against the ethylene gas produced by apples and other ripening fruit by placing your container of bulbs in a plastic bag and sealing with tape or a twist tie.
Bringing the Bulbs Indoors
- The cold period can last from 13-20 weeks depending on the species and exact temperature. Crocus, daffodils and muscari need around 15 weeks, whereas some tulips may require 20 weeds. When the green shoots poking out the top of the bulb are about one inch long, it’s time to bring the container into a cool room indoors.
- Place the container in a shady spot for the first 4-5 days, then move it near a window. The leaves develop and in a couple of weeks buds will form.
- When the buds begin to colour, the container should be moved to the desired flowering spot. Bright but not sunny, free from drafts, away from a heater or radiator and not too warm.
- Keep the soil moist at all times and occasionally turn the container to promote even growth.
Unlike other narcissus bulbs, paperwhites do not require a chilling period to bloom. They are the perfect choice to grow “soilless” in water with only decorative pebbles or beads for support.
- Use a fine quality landscape gravel or marbles. Do not choose gravel with sharp edges, as these may damage the bulbs and their emerging roots.
- Gently wedge the bulbs in the gravel with the tips protruding. The water level must be maintained to just below the base of the bulb.
- Pre-chilled bulbs are great for beginners, since some of the work of chilling them has already been done.
- Most will only need water and warm conditions and they can be flowering in 3-4 weeks.
- Popular pre-chilled bulbs include daffodils, Dutch iris, tulips, and crocus.
- Hyacinths are also very popular, but many people do not realize that they still need to be chilled further and require different treatment.
Hyacinths require 13 to 15 weeks of cold to come out of dormancy, but you can take 5 weeks off this time by buying prepared hyacinths. Prepared hyacinths will need another 8 to 10 weeks of chilling before they will sprout.
Bulbs in Water (The Bulb Vase)
A popular container for growing and displaying forced bulbs in water is the “bulb vase.” These glass receptacles are specially designed for holding large bulbs such as hyacinths.
- Fill the lower section of the vase with water then place the bulb in the upper section with its base just touching the water.
- If using a hyacinth, or other bulb that requires chilling, then place the vase and bulb into a cold, dark place, such as a garage or your refrigerator for roughly four weeks. You should see a well-developed root system and a growing tip emerge from the tip of the bulb. Then move it into the warmth and light so the show can begin.
- The water level in the vase should be maintained at 0.3cm (1/8”) below the base of the bulb.