Where did I screw up forcing my tulip bulbs?

January 31, 2008 8:23 AM

I have tried to force some tulip bulbs indoors this winter and have failed miserably, but don't know why.

I planted some tulip bulbs in October in a shallow container covered in potting soil. Kept the soil moist, and kept it in the fridge until a couple of weeks ago, when I took the container out and moved it to a sunny window. Since then: nothing. Nothing, that is, except white fuzzy mold and fruit flies. Not the vaguest hint of a sprout. What gives? It appears to have been a process of very few steps. Which one of them did I screw up?

posted by catesbie to home & garden (7 comments total)

Probably they were too moist in the fridge. Typically, I just make sure the bulbs are dry and put them in a brown bag, then after six-eight weeks, bring them out and then plant them either in soil or just with gravel/rocks and water and set them near the window.
posted by sulaine at 8:42 AM on January 31, 2008

In the fridge in a brown bag for 6-8 weeks, that is.
posted by sulaine at 8:43 AM on January 31, 2008

we have some extra bulbs from last fall's planting in the bag they came in from the store. they were inadvertently left under a light that is on a timer in an entryway, and they have started to sprout! perhaps setting up a timed light might help to get them started until they can live on sunlight?
posted by kuppajava at 8:46 AM on January 31, 2008

It's hard to say, exactly, but I dug up (HA) the following:

"During cold storage, water the bulbs regularly and keep them in complete darkness." (here) Did you put them in your normal fridge, which is opened to the light frequently? That site says sprouts should have begun before you even remove them from their cold storage.

"Forcing bulbs should be in the “G-stage” before initiating chilling. This term is used to describe a developmental stage of a bulb. G-stage bulbs have completed developing the entire flower shoot inside the bulb. In other words, a small tulip flower bud is present inside the bulb." (here) Maybe you chilled them too soon, before the bud was developed?

"In general, shorter-growing varieties such as the species Tulipa humilis (or the very similar T. puchella) are the easiest to force indoors." (here) Did you pick the wrong varietal? Apparently some are less likely to be successful with this method than others.

"If you don't have room for all the planted pots, try placing the unplanted bulbs in a paper bag in the refrigerator crisper for six weeks (always without fruit in the refrigerator at the same time), then pot them and place them in a 55° F dark room for a month. Then bring them into a 65° F room to grow and flower." (here). Did you give them an interim period before putting them in the sun?

It actually looks like lots can go wrong... Tricky things, tulips!
posted by nkknkk at 8:52 AM on January 31, 2008

I force bulbs all the time, both at home and sometimes at work. It has nothing to do with my job but we have a special walk-in refrigerator just for forcing and I take advantage of it. Tulip bulbs tend to get moldy sometimes, it's really ok, and the fruit flies just want a drink. What's the state of the bulbs themselves....are they mushy? If so, throw them away - you overwatered. If they're still firm they should be ok and may still pop. The main things to remember when forcing in your fridge (file this away for next year!):

You can't use just peat moss, you have to mix in some sand for drainage. Peat moss alone creates excess moistness and wet feet.

Do not overwater, and make sure there's a way for excess water to escape...drain holes on the bottom are ideal. A clay pot is ideal.

Keep the bulbs in the coldest part of your fridge. The ideal temp for a florist's refrigerators is approximately 38 degrees - it's a couple of degrees colder than the average home fridge but a few degrees above freezing.

You do not want any part of the bulb or container to freeze, because even though you're attempting to mimic outdoor conditions and the ground outside does freeze, bulbs have many inches of insulating dirt around and under them, which your bulbs in the fridge at home in their container do not have.
posted by iconomy at 9:13 AM on January 31, 2008 [1 favorite]

Not all varieties work that well for forcing. Research or ask someone in a store about likely varieties if you just chose a random one or whatever was sitting around. Fresh bulbs in excellent condition (firm, undamaged) are best for forcing.

Other tips are to leave the tips of the bulbs exposed when you planted. Use a well-draining mix (2 parts peat moss and 1 part sand is recommended mixed with an equal amount of soil). Handle the bulbs very carefully and don't "pack"them into the soil, they should be gently and loosely planted. They should be kept out of high temps prior to cold treatment, i.e. under 65 F.

With mold appearing over-watering could be an issue. The soil should not become dry but it should be just damp and you don't want to ever soak it or have water pooling in the base of the pot. Is there any mud/mush/liquid at the bottom of the pot? Water less and consider a drainage layer of gravel or perlite at the base of the pot. Poor quality or old/contaminated potting soil could be an issue, the soil is a likely candidate for where the flies came from.

Check your fridge temp for cold treatment, it should be minimum 35 maximum 48F for at least 12 weeks. The pot should be covered with perforated plastic which should eliminate much evaporation and need for watering. A freeze will kill them. I've seen the crisper drawer recommended for this use.

Over warm temperatures and direct sunlight are a problem, especially early on. They prefer indirect though sunny and temps below 60 F. This can be hard to achieve in the winter home. Higher temps tend to lead to fast growth and weak structures rather than not sprouting at all. In your case I'd suspect they got killed somewhere prior to taking them out: bad bulbs, rough or handling or planting too deeply or packing soil too tight, too extreme temperatures, and over-watering leading to rot/mold are the culprits I'd guess.

On preview, I've never tried the paper bag treatment, but I do find that varieties that are known for forcing (i.e. paperwhite narcissus, amaryllis) tend to be easier all around, some don't require cold treatment as well (I had lovely paperwhites this year for Christmas and New Years).
posted by nanojath at 9:18 AM on January 31, 2008

Wow, this is all very helpful! I'll give it another few weeks just in case they decide to give me another chance, but next year I'll make sure my soil is the right ratio and try throwing them in the basement for an intermediate period. Thanks again!
posted by catesbie at 10:27 AM on January 31, 2008