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Back to How To....    |   How to Force Blooms



Winter can be rather dreary for gardeners.  Nothing is in bloom, it is cold outside, and all you can do is wait for spring to arrive.  However, you can “force” certain types of flowers to bloom when you want them to and have flowers all winter. 

Bulbs are a prime candidate for forcing.  You can have any spring blooming bulb blooming in a pot in your house all winter.  You must plan ahead, however.  Most bulbs need eight to fifteen weeks of chilling time before they will be ready to bloom.  That means you need to save some bulbs out when you plant most of them in the fall.  These bulbs need to be kept cool in the refrigerator until they have gotten enough chilling hours to bloom.  It is important to store the bulbs in mesh bags and keep them away from fruits and vegetables.  Fruits, especially apples, and some vegetables, put off ethylene gas as they ripen, which will damage the flowers inside the bulbs.

Amaryllis and paperwhites do not need to be chilled.  Just follow the directions on the package and put them in a pot.  Water in well and put them in a bright spot, and they will grow and bloom all on their own.

Generally, the smaller bulbs such as crocus, grape hyacinths, miniature daffodils, iris, and tulips are easiest to force.  Large, fragrant hyacinths are also easy.  When buying bulbs to force, get the biggest bulbs you can find.  The bigger the bulb, the more flowers are packed inside.  Make sure the bulbs you buy are firm, free from nicks and bruises, and that the roots haven’t sprouted yet.


Choose a pot that is at least twice as deep as the bulbs you are planting in it are long.  Make sure it has a drainage hole in the bottom.  Fill the pot half full of soilless potting mix.

Place as many bulbs in the pot as will fit without the bulbs touching.  Make sure the pointy side of the bulb is up.  A six inch wide pot usually holds up to six tulips, three narcissus, or fifteen minor bulbs such as crocuses or grape hyacinths. Bulbs that have the same chilling and blooming schedules can be planted in the same pot.  Put the bigger bulbs under the smaller bulbs and the bigger bulbs will grow around the smaller ones.

Once you have all the bulbs planted, cover them with potting mix but leave their tips showing.  Water the bulbs thoroughly.  On a paper sack, label the pot with what is in it and the date it planted.  Loosely cover the pot with the paper bag. Place in cool (35 to 45 degrees F), dark storage for chilling.

Keep the soil damp but not wet.  When the chilling is done, you will see roots at the drainage hole and little green sprouts from the bulbs.  It is now time to move the bulbs into a warm room.

Place the bulbs in sunlight when a flower bud appears.  When flowers appear, put the pot out of the sunlight to make the bulbs last longer.  When the flowers fade, toss the bulbs and potting mix in the compost pile.  Forcing the bulbs uses up the last bit of energy in them and most won’t bloom again.

Table 1: How long to chill bulbs to force them to bloom

Type of bulb

Chilling time

Time to bloom after chilling

Daffodils

12-15 weeks

2-3 weeks

Tulips

10-16 weeks

2-3 weeks

Crocus

8-15 weeks

2-3 weeks

Grape Hyacinth

8-15 weeks

2-3 weeks

Iris reticulate

13-15 weeks

2-3 weeks

Snowdrop

15 weeks

2 weeks

Hyacinth

12-15 weeks

2-3 weeks

 

Poinsettia is often forced to cause the brachs to turn red and the blooms to come out around Christmas time.  Poinsettia and many other plants bloom according to the length of the night each year.  The easiest way to force them is to control that factor and trick them into thinking it is time to bloom.

You will need a place that is absolutely dark, such as a closet, to put the plant in and simulate night time.  You will also need a grow light and a timer switch.  The timer will control the light and make sure it comes on at the same time each day and goes off exactly twelve hours later.  Do any watering or checking on the plant during its “daylight.”  If you let light on it during its “dark” you will have to start over in forcing the plant.

When forcing plants to flower, you need the correct temperature during the day and during the night in whatever space you have placed the plant.  This varies by plant, but you won’t get a bloom unless you get it right.  For poinsettias, it needs to be 65-70 degrees F during the day and 60 degrees F at night. You will need to place the poinsettia into the dark around September or October to have it be red for Christmas.  Reduce watering and do not fertilize during this period to induce the plant to go dormant.  Once the brachs turn red, you can reduce the amount of dark and start fertilizing it again.

If you want to keep your poinsettia year after year, you will need to duplicate its natural life cycle to keep it alive.  Once blooming has ceased after Christmas, you will need to limit the amount of watering so that the plant will go dormant in the spring.   While the plant is dormant, prune back to about six inches from its base and repot.  Water in well and set in a bright spot.  Fertilize with a balanced liquid fertilizer once a month.

Poinsettia plants can be kept outdoors in a protected sunny area during summer, if desired. Pinch out the tips to promote branching of new growth until about the middle of August.

In September, begin the cycle of dark and light to get it to bloom again by Christmas.




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Gardening-tip:



When to Water

If you can, it is always best to water early in the morning. This allows the plant's leaves and flowers to dry off as the day warms up.

If you water at night, the plant stays wet for hours in the cool, which are prime conditions for fungi and other problems to set in.


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