They stay wet and rot.

Bulbs outside are able to quickly drain they very little water they receive away and/or stay VERY dry in the frozen ground.

It takes much longer to thaw outside in the ground than in a pot.

If bulbs are stored out of the ground, they need to be stored dry with no soil.

Keriann~

You can grow bulbs in containers and leave them outdoors but it is best to keep them where they are more or less out of the weather. Potting soil tends to stay too moist - one of its attributes is to be moisture retentive - so store them somewhere dry (but cold enough) until the bulbs start to emerge from the soil. I use my carport, but the garage or a storage shed, etc., should work too.

As noted in the previous post, it is more a case of the freeze/thaw issue than it is just freezing. Even under pretty cold temps, bulbs in containers will survive as long as they are kept relatively dry. You just want the soil barely moist to the touch.

I tried bulbs in containers last year and put the containers in my garage, some sprouted....most died and none bloomed. This year I tried again but instead of putting them in the garage..I buried the pots in the ground. Also I took my regular potting soil mix and mixed in A LOT of perlite and quite a bit of sand so that the soil would drain very fast. So far so good....everything is sprouted up and I know I will have some blooms because the hyacinth is already showing buds. If the only way you can grow bulbs in containers is by leaving the container outside I would definitely amend your mix to drain very fast

Instructions for forcing bulbs usually say to plant them right at the top of the soil, this does make them sprout but also makes them more vulnerable to insects and mold/fungus. Other than that, I agree that pots simply filled with potting soil tend to not have enough drainage. Next time I try growing in pots I'm going to try gravel in the bottom few inches plus dilute the potting soil with perlite.

Adding gravel to the base of a container planting will in fact impede drainage, not improve it. Any time water encounters a layer of distinctly different size and texture, it affects the flow. What you are accomplishing by adding a layer of gravel is raising the parched water table - the lower level of potting soil will stay wet/saturated longer and will be closer to the bulb roots, creating increased potential for rot issues.

Adding perlite may help but it is so light it often 'floats' to the top of the soil surface, defeating its intent. Adding a coarser bark component would be better or a heavier fine gravel (not sand) or a high-fired clay product like Turface.

You might want to check the Container Gardening forum to research the best container soils and planting methods.

Dormant bulbs do not have live roots

Therefore they can not drink water

Therefore they have no need for water

Therefore water makes them rot

Dormat bulbs will rot in even 'slighty moist' condidtions. That is why man of us do not store bulbs in soil, even the humidity in a house can rot bulbs in 'dry' soil

Keriann~

Ummmmm.......spring flowering bulbs are dormant in summer. Once soil temperatures cool, root development begins almost immediately - that's why they are most often planted in fall. And growing roots DO need moisture. Just not excessive amounts of it.

This is true whether the bulbs are planted in the ground or in containers. Planting the bulbs, regardless of situation, is not the same as 'storing' them.

hmm I would agee to disagree.

Spring flowering bulbs in the summer are not dormat and are recharging their bulbs for next year, so yes roots are present and they need water.

I was more concerned with Spring bulbs in the Winter when they are dormant. Yes, you can force bulbs at almost any time after they have a dormant period but tulip, daff and other Spring bulbs are fast asleep in Dec (I live in Zone 5) and do not a have a need for water.

Keriann~

Keriann, I don't wish to get into an argument but it may help to read up on how bulbs grow -- I think you have some misconceptions.

Spring flowering bulbs are indeed dormant in summer. From the University of Illinois Extension office: "Once the foliage dies back or matures in the late spring or early summer, the bulb is dormant. Summer is the dormant period for spring bulbs. As the foliage dies back, the roots that nourish the bulbs also die back. With fall rains, the bulb comes out of summer dormancy and roots begin to grow again to provide the bulb nutrients and moisture." Once the foliage has died back (the recharge of bulb energy has been completed), the bulbs enter a period of stasis or dormancy. The roots do not grow during this period and water needs at this time are low. This is why instructions for growing and caring for bulbs typically state that they are best sited where regular summer irrigation is light. Too much water at this time, when they are not actively growing, can be harmful.

As the temperatures cool in fall, the bulbs begin to "wake up" and the roots begin to regrow. Interestingly, this is also the time of years when rains become more plentiful as well. The roots will continue to grow and elongate through fall and into winter until the soil freezes. In warmer climates the soil may never freeze and root growth continues unchecked. You may think your bulbs are "fast asleep" but they are not - they are busy growing underground. And sometimes aboveground as well -- that's why we get so many posts here from folks concerned about bulb foliage - daffs, tulips, etc. - poking above ground in midwinter, long before bloom season. If they were fully dormant at this time, why would they be producing any top growth?

Check any spring growing bulb resource and they will confirm what I have stated above.

As to the need for water in winter, the University of Minnesota has this to say about growing spring bulbs in very cold snowy climates: "Extreme cold climates, where the frost can reach several feet into the ground such as Minnesota, require very early planting as well as regular watering to stimulate root growth. Many summers here are droughts and there can be seasons with little or no rainfall before the ground starts to freeze in late Autumn. ... Six weeks of watering/rainfall is essential for root growth. Without the root growth BEFORE the ground freezes, all spring bulbs will be frozen and lost during our extreme winters."

hmm... it looks like I have been mis-informed over the years.

I am going to check out that website

Thanks!

Keriann~

I overwintered in containers this winter (in my attached garage) and just moved them outside into my windowboxes. All the tulips sprouted, and now are green and growing taller (around 5-6 inches.) I don't want to speak too soon, because they have not bloomed yet, but they seem to be growing/thriving. I used potting soil, and put broken pieces of pots on the bottom for drainage. I watered them once when I planted them in late September, and then once a month there-after (I think I even missed a month.) They did not get a lot of water at all... I had read that this was the key to keeping them from rotting. I also bought high quality tulips from tulip world.

joannemb, is this the right time to move the containers with tulips outside now? Mine are sprouting and thriving in the containers too but I am not sure when it is a good time to take them out safely.... mind you, the weather is probably not going to do as much damage as the deer might!!! Sigh...

ostrich,
I know! I'm worried about the deer.... My planters are on my front porch though---a very bold deer would have to come right onto my front doorstep to get at them (but they are getting bolder and bolder these days...)

Being that this is my first time overwintering, I asked several questions about when to bring them outside. I would have rather left them inside as long as possible as I actually want them to bloom later (late April if possible.) No one really gave me a straight answer except one person did mention if I didn't get them used to the sunlight now they would get sun scorched later on. So that was what finally persuaded me to bring them out. Good luck---we will have to compare tulip notes and pics (I'm crossing my fingers that mine do indeed bloom) :)

Having bulbs overwinter in outdoor containers in zone 5 or colder can be quite tricky. Been there, done that myself. It is easier to force them in pots in an unheated garage or cold cellar, and then put those smaller pots inside your larger decorative container outdoors in the spring. Several of you mentioned that you do something similar. That way, moisture in the pots can be controlled over the winter, not too much or too little. Gardengal has very good advice. In order to be hardy over the winter, bulbs have to form good root systems before the ground is frozen. The narcissus family is especially prone to rotting in damp soil if planted too late in the fall.