Tips for forcing bulbs in pots to achieve that spring ‘wow’ factor
By Lloyd Thompson
WSU Chelan/Douglas County Master Gardener
One of my favorite times of the year is spring, when everything is coming out of its winter doldrums. Spring bulbs are always one of the early signs that I look forward to; these include snowdrops, hyacinths, daffodils and tulips. The sudden emergence after the snow melts and the vibrant bright colors always put a smile on my face.
The only problem is that it sometimes seems to take forever for that snow to melt and the temperatures to warm enough to start those bulbs on the path to blooming. If you are as impatient as me, there is a way to get an early peek at spring even before the snow melts.
Spring bulbs require a vernalization period before they can start to bloom, basically an extended cold treatment that makes sure bulbs don’t start to grow early before winter is over. The bulbs require temperatures around 35 degrees Fahrenheit for about 15 weeks. After that, warming temperatures will cause the bulbs to start sprouting and will bloom in about four weeks.
This process can be created artificially, which is called forcing, where you plant bulbs in a pot and then force them to bloom early. Who wouldn’t like a small pot of tulips or daffodils sitting on their counter or desk during the winter months?
There’s several steps that are required for forcing spring bulbs to be successful.
The first step is getting the bulbs; they are usually available to purchase starting in late August until early fall. Then you have to decide on when to plant the bulbs and start the vernalization process or simply start the vernalization process and plant the bulbs later.
I like to do the latter because I can place a bag of bulbs in the refrigerator, and it takes a lot less room than planting the bulbs in a pot and then trying to find space to start the cooling process. I am usually really busy in September and it’s often too warm to place the bulbs outside yet. So, leaving the bulbs in the back of the refrigerator until cool weather arrives is easier for me.
The bulbs need to continue the vernalization process (cold treatment) around 15 weeks total. Part of that can be in the refrigerator; the rest of the 15 weeks will be in a pot.
Using the refrigerator method is handy, but a more gradual cooling over an extended period may give better results. This is possible if you have an extra refrigerator that you can dedicate just to the bulbs, slowly lowering the temperature to 35 degrees Fahrenheit over several weeks. I wait until it cools down outside and then I take the bulbs out of the refrigerator and plant them in pots. I prefer using clay pots and clay saucers versus plastic because the additional weight keeps the pots from tipping over as easy. You can select from a wide range of sizes and types of pots that can be decorated.
I use a general potting mix with a little builder’s sand and perlite to help with drainage. Then I place the pots outside in a place so they are easy to get to when I want to start warming them up to bloom. Remember to water them enough to keep moist but not wet. Think about the possibility of snow when making your site selection, it is hard to dig them up when covered in snow and frozen to the ground.
About four weeks before you want to have the pots blooming, move them to a warmer space. Since these are spring bulbs, a temperature range of 50-60 degrees Fahrenheit usually works best. A cooler space in the garage or basement can work as a growing location. Most home thermostats are set to the upper 60s to 70s and bulbs grown at these temperatures tend to be leggier and the blooms not as robust.
I usually try to stagger out when I start taking the pots of bulbs out of the cold treatment so I can have blooming pots over a longer period of time. After they bloom, forced bulbs can be planted in the ground but they usually don’t do well after the stress and can be just disposed of instead.
So if you want an early flash of color and a sign of spring, go grab some spring bulbs and try forcing them to bloom early this year.