Plants survive generation to generation in the wild because they are programmed to grow, bloom and produce seeds when the conditions are favourable.
Growers use this knowledge to manipulate temperatures and daylight hours to bring plants into bloom through out the year.
At present time poinsettias are being grown in commercial greenhouses. Growers will drape the beds with blackout cloths in the late afternoon and remove the material 12 to 14 hours later. This routine will continue until it is possible to see the formation of flower bracts; six to 10 weeks.
If the dark cycle is disrupted then more weeks will be added to the process.
It is possible for home gardeners to force their poinsettias into bloom using the same method. Cardboard boxes or dark closets can be substituted for blackout cloths. It is a matter of remembering to place the plant in darkness at the same time every afternoon and putting it in a sunny location during the day.
Spring bulbs are another plant that is easy to force. They require a cold dark treatment, similar to being placed in the ground. Choose bulbs that bloom early in the season: hyacinths, daffodils, crocuses and early blooming tulips. Purchase the largest bulbs available to ensure the best blooms.
Spring bulbs can be forced in soil and a pot or a special forcing jar. When using a pot ensure that it has good drainage holes. Place a thin layer of moist soil on the bottom of the pot then set the bulbs in pointy side up.
Next, cover with more moist soil. For a fuller display add another layer of bulbs by positioning them between the tops of the first layer then cover with more moist soil. Not all the bulb has to be covered.
Once planted, place the container into a cardboard box or paper bag and seal it. Place the package in a cool area, just above freezing. Cold rooms and refrigerators work well as long as they do not contain fruit that gives off ethylene gas as it will inhibit the bulb’s blooms.
Periodically open the bag or box and water the container if the soil is dry. Once the bulbs have a one-inch (2.5-cm) sprout they should be taken out of cold storage. Place them in an area that is cool with bright light. When the plants are green and growing well, move them into a warmer area in full sun. Placing the plants into a cooler area when they are in bloom will ensure that the bloom lasts longer.
Always keep the soil moist but not saturated. If the soil becomes too dry the flower buds die. A saturated soil will cause the bulbs to rot.
Forcing jars have a wide bottom and a half-ball on top that holds the bulb. There are specific styles of jars for hyacinths and daffodils.
Place water in the bottom of the jar. It should come within an inch (2.5 cm) of the bottom of the half-circle. The bulb is then placed in the bulb holder, pointy side up.
Carefully place the jar in a bag or box in a cool area the same as with bulbs that are planted in soil. If the forcing jar is clear it is possible to watch the bulbs root development and its top growth.
The storage temperature and variety of bulb makes a difference in how long it takes the bulb from planting to bloom. Expect it to take between six and 10 weeks.
It take isn’t hard to force a plant into blooming at a different time of year but it does take time and attention to detail.
Linda Tomlinson is a horticulturalist and educator living in Rocky Mountain House. You can contact her at your_garden@hotmail.com