How to start the forced bulb season early? Pre-chilling!

This blog post should be a short one.  Referring to my last blog on forcing bulbs, I'll explain how I'm going to keep my pots chilled.  If this is successful, then one might get up to 5 or more pots, one after the other, per year.  That's 2-4 months of blooms, depending upon conditions and what flowers you plant.  For us, most years this would extend into spring, when things are starting to come back to life anyway outside.  For me, the questions come down to what does it take to provide the chilling, how much hassle is it, and what does it provide me. Time will tell about the provision. For what it takes, not wanting to use the fridge, I'll use a cooler and re-freezable ice. My cooler will be The Bulb Box, which is much more insulated than standard coolers.

I think I'll define another acronym here as it will no doubt show up periodically.  It's EE and stands for Electrical Engineer.  As an EE by profession, I have thermo-couples and meters to test the chamber temperatures.  From it I found an interesting thing about the "re-freezable ice" containers.  Bigger isn't always better!  Based on size, I would have thought that the larger "blue" ice would have worked better than an equivalent amount of smaller ones.  My reasoning was that the little ones spent more of their size in plastic instead of re-freezable material.  What it turned out was that on the big ones, the plastic was enough of an insulator and they had enough insulating air bubbles that they could remain partially frozen yet lose a lot of their chilling capacity. I went back to the store and shook (fairly hard) a bunch of the biggers. After a little shaking you could hear and feel the air bubble in some of them. So, they're not all filled full!

Back to bulbs. Here is my 2 pot set up.

First layer

Second layer

Blue Ice final layer, then cover with base from The Bulb Box

Starting in mid August, I was swapping the blocks twice a day. As of early September, I've been doing it only once a day. The room temps have been varying from 65F (18C) at night to 77F (25C) during the day. The chamber temps have ranged from 36F (2C) to 47F (8C). With the sphagnum moss as insulation, the temps of the bulbs have been staying pretty steadily at 45F (7C). Between the chamber and the moss, they average out the temperature swings so much that I probably could have gotten away with only one ice change per day from the start and a bulb temperature of 50F (10C). As of mid September, I moved the operation out to the garage. It sounds like more of a hassle than most would want to do, but an ice change is only taking me 1 minute, 30 seconds, not rushing.

I should point out that as well as insulating, the sphagnum moss is acting as an absorbant so as the moisture freezes out of the air on the ice, then melts as the ice warms, it doesn't provide the bulbs the moisture needed to root. As part of the experiment, I'm going to forget to swap the ice for a few days to simulate having gone briefly to Maui with my wife, leaving the kids with the grandparents. :)  Of course this shouldn't make any significant difference as its the same as the bulb growers already do when they pre-chill their bulbs, then ship them.

Note1: This technique takes 3 extra spacers not included with The Bulb Box. If you need them, go to the home improvement center and get 3, 10 inch sections of their 3/4  by 3/4 inch square wood. Its about $0.50/foot.
Note2: The final version did away with the tin foil and added 2 small re-freezable ice blocks to fill in the area available.

How to force more bulbs in the same space

Every year, I come up with some gardening experiments, usually associated with season extension or forcing flower bulbs.  This winter is no different.  I have a few bulb experiments that I'll detail in a few blogs.  I know it sounds kind of crazy, but I already have some bulb experiments planned a year out, for winter 2011-2012!

This year's mental daydreaming resulted in 3 different experiments.  Normally I just plant my bulbs in their pots and put them in The Bulb Box for their chilling.  The pots take up a lot of room, so my first experiment is to see if I can get more bulbs chilled in my limited space.   By manipulating the chilling, water, soil and timing requirements perhaps I can get 3-5 forced pots out of a 2 pot space.  If I'm trying to sequence 3-5 pots through, I'll want to start early.  If sucessful, I might have tulips blooming as early as just before Christmas and continuing till the end of February!


Trying to start this early dictated my second experiment.  I'll need to start the chilling during the warm summer season.  I won't be able to use the refrigerator because it's already full.  Also, fruits and vegetables can give off ethylene gas which causes problems with bulb development and, as a general rule, we don't mix food with inedible or poisonous items.  I'll use The Bulb Box as normal for the cooler weather; but to jumpstart the season during warmer weather, I'll put the base of The Bulb Box on a shelf and use the lid  with re-freezable ice to create a highly efficient ice box.


The cedar sides on my outside raised beds are getting too old and need replacement, so I've dug up my bulbs.  This leads to my 3rd experiment, sequencing bulbs through the garden and into my forced flowers.  I'll blog about them later.


Bulbs go dormant during the summer presumably to live through the relative drought conditions.  To avoid flowering again when the fall rains arrive, they use the chilling requirements to tell them spring as arrived.  Normally, I just plant the bulbs I want to flower in the pot, water and chill them.  With the drought/chilling distinction, I'm going to look at the pot as a chilling container that holds more bulbs than will eventually be forced in it.  Rather than describing it in English, I'll try to in pictures.


The bottom layer:

The top layer:

These are red tulips, about 24 per pot, and 2 pots.  Normally, I force about 8-10 large flowers per pot, so this represents 5 pots of forced bulbs.  In mid October, after 2 months, I'll start shifting them over to potting soil, some moistened, with 2 layers of bulbs and soil per pot.  The pictures show a lot of sphagnum moss.  I've chosen  it to help insulate the bulbs, evening out the temperature they see,  absorbing water before I want the bulbs rooting. and allowing some air flow to help keep down any mold issues.  I hope it works!

Stay tuned!!!

Darrell