Forcing Spring Flower Bulbs in the Winter Sun & Cold

The sun is out and I am itching to get my hands dirty.  One of the advantages of having a garden club for students for over 15 years is that during the winter, I was still playing with worms, planting bulbs, and planning for spring.

Getting ready to force paperwhite bulbs. © Carol Labuzzetta, 2018

Missing an Activity

This is the first winter since 2004 that I have not had to plan those student activities. Do I miss them? Yes. And, no. But, this post is about what I miss. I miss anything that has to do with teaching the younger student. I think grades 2-5 are my favorite. They are like little sponges, soaking up information with curiosity and enough lack of inhibition to ask anything that comes to their minds.  This is a wonderful attitude to have when learning. Unfortunately, based on my experience, somewhere between sixth and twelfth grade for many students, this attitude changes but that is a post for another day.

As I said one of my favorite activities to do with students is forcing bulbs.

Some common flowering bulbs are tulips, daffodils, paperwhites (related to daffodils), and hyacinths.

A daffodil blooming at NWIS, Spring 2019. © Carol Labuzzetta, 2019

Forcing a flower bulb means that you are making it grow out of season. Certainly, having a flower grow in the throws of winter gives this definition of meaning.  Forcing does stress flower bulbs and I’ll return to that thought at the end of my post.

Poinsettias were always part of the Holiday Plant Unit, too. 

Usually, we forced bulbs in December as part of a holiday plant unit. But, I have done it in January and February, as well. In planning for this unit, I gathered the bulbs we needed in August. Typically, I  chose paperwhite bulbs for they do not need a cold period. But, as the years progressed and I had “repeaters” or students that joined, again and again, I added some other flower bulb types to those that had already forced a paperwhite.  These were usually hyacinths or tulip bulbs. Those two bulbs, and most others, do need a cold storage period of 8-12 weeks. This is a period of time when the bulbs are kept cold, in place such as a refrigerator, that will mimic winter.

Steps to Forcing Bulbs:

  1. Gather bulbs to be forced. Plan ahead. Most bulbs need a cold storage (or stratification) period. Paperwhite and amaryllis bulbs do not.

You might know that spring-blooming bulbs need to be planted in the fall. The purpose of this is so that they can grow roots and be ready to grow in the spring once our days get longer and warmer. The placement of a bag or carton of bulbs in the refrigerator for the specified period of time mimicks this outdoor period.

2. So you are ready for when bulb planting day arrives, you’ll need to gather some other materials.  These are pearlite or vermiculite, clear plastic cups (16 oz.) work best, water, and the bulbs.

The advantage of the clear plastic cups is that the students will be able to see the root development (what happens first) and the waterline (so the bulbs are not sitting in water).

Did you know that flower bulbs are amazing plant structures? They are! Bulbs are actually modified stems. The modification is that they have the ability to store food for the plant in the form of starch. There is enough “food” in each flower bulb to grow and sustain the plant for an entire year!!!! Amazing!

3. Each student needs a plastic cup filled with perlite or vermiculite at least 1/2 to 2/3rds full, a bulb, and some water.

4. The bulb goes in basal plate down. The basal plate is the flat, hard surface from which the roots of the bulb are found.  The pointy side or sprouted side of the bulb is pointed up towards the ceiling. The bulb can be buried in the vermiculite but not entirely. The top third of the bulb should be visible above the potting mixture.

5. Once the bulb is placed in the potting mixture, the bulb can be watered sparingly. Bulbs should never sit in the water given to the plant for this will encourage rotting. The bulb’s roots will grow to reach the water.

Things to Notice

Over the next several weeks (about six) the bulb will grow, change, and eventually flower. The first thing to happen is that the roots will grow. Sometimes they grow so much that the bulb looks like it has been lifted on stilts!

The next thing to notice is that any sprouting of the stem that might appear white when planted will rapidly turn green as the bulb begins to photosynthesize!

Paperwhite Growth, 2015. © Carol Labuzzetta, 2015

Finally, the bulb will shoot up stems and leaves, buds will form, and the delicate white flowers will bloom. This whole process takes 6-8 weeks. If planted in mid-December, students can enjoy flowers around Valentine’s Day. If planted now, they will have flowers in six to eight weeks, before we have flowers blooming in the northern latitudes outside!

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Measuring Paperwhite Bulb Growth Many Moons Ago. © Carol Labuzzetta

Yes, I am kind of missing the bulb unit for Garden Club this year. Oh, wait! I think I might have some bulbs in cold storage! I can force some bulbs tomorrow! Happy Planting!

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