Forcing bulbs for early spring flowers

As winter settles in with days getting colder, Michigan skies get cloudier, we gardeners start to get antsy for the beginning of the growing season and longing for spring flowers to bloom.

We can give ourselves a late winter treat by planting bulbs indoors using a process known as forcing.

Forcing is a method of growing plants outside of their normal flowering season. By using certain techniques, we can coax plants into flowering. Some patience will be needed because the process takes a few months. But that’s OK since that is when we’ll really be hankering for some colorful blooms.

Spring-flowering bulbs such as tulips, daffodils, hyacinths, crocuses, etc are tailor-made for forcing. Those types of bulbs are easy to plant in pots and are available this time of year.

We are nearing the end of the planting season for spring flowering bulbs so some types of bulbs may be sold out. Most garden centers however still have some bulbs available even though the selection may be limited.

Just a few days ago I saw several varieties of bulbs on sale at a large retailer and grabbed a bag.

The forcing process occurs in two stages. During stage one, the bulbs develop roots and buds. Stage two is the actual flowering phase.

To get the process started we have to mimic the conditions that bulbs in the ground would be subjected to during winter. No two winters are the same but the bulbs need a minimum amount of exposure to cold temperature in order to bloom later. 

Stage one cold treatment works best at 40 degrees F. It just so happens the vegetable drawer in a refrigerator provides just the right temperature. 

Other more traditional cold treatment places include a cold-frame, an unheated cellar or basement, an unheated garage or even a pit dug into the ground and covered with straw, just so long as the spot does not freeze.

Commercial floriculturists have developed intricate cooling schedules and specialized cooling rooms, but for our purposes the crisper drawer works just fine.

The minimum cold treatment lasts from 12 to 14 weeks. So keep that in mind if you decide to use your fridge.

Also be aware that apples during storage give off small amounts of ethylene gas which disrupts the bulb development so no apples should be in the refrigerator with the bulbs during the cold treatment period.

Regular 6-inch or 8-inch pots are ideal for forcing as long as they have a drainage hole. The bulbs must be kept moist but too much water will cause them to rot.

Pot up your bulbs using a commercial potting mix, preferably one with plenty of perlite to help with good water drainage.

Pour in a couple inches of potting mix into the pots. Estimate the final depth of the mix so that the tips of the bulbs are sticking out about a quarter of an inch. Leave around a half- to quarter-inch of space below the rim to allow for watering. Do not press down the soil, allow it to stay as loose as possible.

Gently place the bulbs evenly in the pot with about a half of the bulb's width apart. Again, to avoid compaction, do not press the bulbs into the soil, the idea is to have the soil as loose as soil as can be to encourage fast root development. 

Small bulbs like crocus, grape hyacinths and snowdrops are planted about an inch below the soil.

Another tip: When placing tulip bulbs, orient them so the flat side of the bulb is facing outward. That way once the plants are up, the leaves will all be growing to the outside nestling the flower stalks in the center of the pot.

Once the bulbs are potted, water them well and allow all free flowing water to drain out. Wrap the pot in a plastic bag with some breathing holes poked in it. Place the wrapped pot in the vegetable drawer. 

Since refrigerators will tend to dry out produce and other food items, your pots will be prone to drying out too. Never let the soil get too dry, check your pots every couple of weeks or so to make sure they are still moist. 

No fertilizer is needed for this process since the bulbs have all of the nutrients they need stored inside. 

Mark your calendar for 12 weeks from potting. After the allotted time, take the pots out and look underneath to see if roots have formed near the drain holes. If not, give it a couple more weeks in the fridge.

Stage two of the forcing process involves the emergence of the flower stalk and flowering. Actual blooming will take two to four weeks or so.

Remove the pots from the refrigerator and place them in a moderately cool, 50 to 60 degrees, sunny place until you see green shoots growing. Once there is active growth, you may move the pots into your living space. 

If you want to take it one step further to help the blossoms last longer, move the pots to a cooler spot each night bringing them back out during the day.

With a little bit of enjoyable gardening work now, you’ll enjoy an early foretaste of spring!