Forcing Spring Bulbs for Indoor Blooming
Put an End to Cabin Fever
It's the middle of winter. Everything appears to be dead and lifeless and a dull gloom seems to hang over everything. Your thoughts drift to warm spring days with the lush green of your garden and new growth ushering in yet another year of prolific growth. The bare starkness of winter seems to creep in from everywhere, permeating everything and putting an icy grip upon everything in site. Some call it the winter doldrums, while others call it cabin fever. Luckily, you had the foresight to take out some insurance last fall against "Old Man Winters" icy grip and packaged up some anti-biotic to use against his gloomy, icy plague. You had the foresight to assemble some explosive little bundles last fall and now they are reeking havoc with old man winters plan to lay waste to your sanity as they explode cheerily on the table, chasing the last vestiges of gloom from the room and filling the house with their sweet odor.
But what is this miracle weapon anyway and what is it called. The weapon is "Spring-Flowering Bulbs". The very same ones that break winters death grip each spring and usher in a new year of promise and growth. The name of this miracle weapon is not a thing at all but rather a process called "forcing". Forcing is nothing more than a process whereby nature is coerced into working with you to defeat the forces of winter by blooming when they normally would not do so.
Forcing is not new and has been used for centuries to get bulbs such as daffodils, hyacinths, tulips, crocus and others to bloom when nothing else is growing. With a little planning, you can have an effective weapon against old man winter from late November until bulbs start blooming normally outside in spring. But before you start filling every medicine bottle (flower pot) in site with an effective remedy against this plague, we need to familiarize ourselves with a few directions and dosages in order for our "medication" to work effectively.
First thing we need to know is that there are really only two types of bulbs for forcing. Those that need "pre-chilling" and those that don't. The bulbs that need pre-chilled are the ones that you would normally plant outside in the fall to over winter in the ground. These include daffodils, hyacinths, tulips, crocus and many others. They rely on a cold period to develop roots for the following springs growth. Then there are those that do not require pre-chilling. These bulbs normally grow in warm climates and have never known winter. These include amaryllis
, freesia
, tropical narcissus and paperwhite. All of these bulbs would normally grow in zones 8 - 10 where freezing temperatures don't generally occur.
With each of these bulbs you can either plant them in soil or a bowl of pebbles to hold the bulbs upright. These will normally bloom within 4 - 8 weeks (depending on variety) after planting on their own. In order to help keep the stems short and stocky, here are some tips:
- Only choose top quality, blooming size bulbs. Many cheaper bulbs available will be of inferior quality and may not be of appropriate size to bloom at all, thus giving poor results or no blooms at all.
- Provide indirect light and cool temperatures of around 50° F for the first two weeks.
- After that, provide warmer (65° to 70° F) and brighter conditions. But limit direct sunlight to not more than an hour or two each day until blooming commences.
- To prolong the blooming period, move them into a cooler environment at night (around 55° F to 60° F).
- Avoid drafts and avoid sitting them on or near radiators and heat registers.
- If you're planting in water, never let the water cover more than 1/4 to 1/3 of the bulb.
When planting your bulbs in soil, you need a soil that is both well drained and has some "firmness" to it. The reason for this is because when forcing bulbs, very little of the bulb will be underground. Therefore the soil will need to be firm enough for the roots to hold the plant upright with a heavy bloom. Most growers recommend a mix of 1 part builders sand, 1 part garden soil and 1 part peat moss. If you plan on using garden soil in your mix, I suggest that you sterilize it first (feel free to write for instructions if you wish) to kill any weed seeds and diseases. You do not need to add any fertilizer at this time.
While all spring flowering bulbs can be forced, some are more difficult than others. Hyacinths, daffodils and amaryllis are generally the easiest with tulips being slightly more difficult. But most bulbs can be forced with proper treatments and without any special ability on your part. The following steps work for both hardy and non-hardy types, with proper notations when needed. But remember the non-hardy types do not require pre-chilling and will be damaged or destroyed by cold temperatures.
With all bulbs, choose only top-quality, blooming sized bulbs that are firm and free of blemishes. Have your planting media ready, whether soil or pebbles. Choose your planting containers
and have them clean and ready. For soil planting, any container will work as long as it has adequate drainage. Bulb pots are traditionally used for forcing bulbs. Bulb pots are generally shorter in relation to their height and look better, but they are not necessary for success. Don't forget to have gravel or chips handy to put in the bottom of the pots for drainage.
Hyacinths
Hyacinths are among the easiest spring bulbs to force and can be forced in water or soil. Potting is generally done in September or October and the blooms will normally appear in about 4 weeks after they are brought out of their chill period. Generally, you want to allow approximately 8 weeks to chill Hyacinths. For Christmas blooming, many suppliers offer "pre-chilled" bulbs and they will come with special instructions for planting.
The table below lists some of the more popular Hyacinths suitable for forcing, along with bloom color and suggested planting times and when to start bringing them out of chilling.
All varieties of Tulips should be planted no later than the end of October in order to allow adequate time for the roots to develop. The dates show above are the earliest that pots should be brought out of chilling if planted towards the end of October. Tulips will generally start to flower in about a month after being brought out of chilling. But variations will occur, depending on variety, growing conditions and methods.
Materials Needed
Before you start potting, you will need to have the following items ready:
- Bulbs for forcing.
- Clean pots ranging from 4" to 8" in diameter (preferably bulb or azalea pots)
- Soil mix (1 part builders sand, 1 part soil and 1 part peat moss). Extra fertilizer is not needed now.
- Drainage material, such as small pebbles or broken pottery.
- Pot labels and marker
. These can be plastic, wood, metal or anything else that you wish. - A thermometer for checking temperatures is highly recommended.
Planting
Try to start your planting so that you will be finished by the end of October.
- Place a 1-inch layer of drainage material in the bottom of the pot for good drainage.
- Add enough soil mixture so that when the bulbs are placed in the pot there will be approximately 1/2" of space left at the top for watering and place the bulbs in the following manner:
For Daffodils and Narcissus
Plant the bulbs so about one-half of the bulb will be above the soil line. Plant 3 or 4 bulbs in a seven inch pot.
For Hyacinths and Tulips
Allow only the tip of the bulb to show above the soil line. Tulips, along with having a top and bottom, will generally have a somewhat flat side on each bulb. Place this side towards the outside of the pot. For Hyacinths, plant 3 or 4 bulbs in a seven inch pot or one in a four inch pot. For Tulips, plant 3 bulbs in a five inch pot or 5 in a seven inch pot.
For Small bulbs (Crocus, Snowdrop, Grape hyacinth and other small bulbs)
Plant several in a pot, leaving about a fingers width between each bulb and about one inch below the soil surface.
With the bulbs all placed in the pots:
- Plant all of the same kind of bulb in each pot as each species and variety will have different requirements and blooming periods.
- Finish filling the pots to their proper depth on the bulb and lightly firm the soil around the bulbs. make sure there is at least 1/2" of space left in the pot for watering.
- Label each pot for future identification.
- Water thoroughly until water drips out the bottom of each pot.
After you have potted your bulbs, you will need to put them to bed in a cool environment to chill and form roots. This is when dormancy breaks. The desired temperature range is 35° F to 45° F, with 40° F. being ideal and not exceeding 50° F. Any place that can provide these temperature conditions without freezing for at least three weeks will work, whether it is a crawlspace, unheated garage or spare room or wherever they can get a proper chilling and the temperature doesn't rise above 50° F. Two of the handiest methods are to store them outside in a cold frame or in a refrigerator.
I personally find a spare refrigerator to be the handiest and most convenient and can often be found free or at little cost. Just use a thermometer to set the thermostat ahead of time to 40° F. first. If you are using a refrigerator that you also store food in, do not store your pots and/or bulbs in the presence of fruits and some vegetables, as these give off ethylene gas that can damage many bulbs.
While you can sink the pots directly into the ground or group them together and cover them with an insulating material such as leaves, straw, etc. However, retrieving the pots can be difficult in the dead of winter and it can be difficult to guarantee the pots get a proper cool period before the weather turns cold.
For a more protective and regulated outside storage, start by locating an area that is on somewhat higher ground than the surrounding area, in a shady location or on the north side of a building in order to maintain cool temperatures. Dig a cool-pit in an area that drains well and is approximately eight to ten inches deeper than your tallest pot. Make it long enough and wide enough to hold all of the pots you plan to force plus roughly four to six inches extra on each side. Place approximately 2" to 3" of leaves in the bottom of the "pit" and sit all of your pots on top of these. Next, stuff the areas around and between the pots full of leaves and then another 6" to 8" of leaves on top of the pots or until the pit is full. The leaves will help insulate the pots and prevent them from freezing down so that they can be easily removed later. Over the top of this, the old way was to cover the whole thing with 3" to 4" of sand. I've found that covering the pit with a sheet of exterior insulating board with foil on one side (the rigid foam insulation used to cover the exterior of houses) laid over the hole with the foil up will provide excellent temperature stability. It further helps to keep the leaves from getting wet and freezing together into a frozen mass, so removing the pots later is easy.
Another time-honored method is to place the pots into a cold frame and use leaves as in the pit method above. The cold frame should also be placed in a shady location, or on the north side of a structure to maintain cool temperatures. Normally, the sashes are removed. However, I have found that if you will secure the sashes where they stand open 4" to 6" the cold frame will be able to remain cold but the leaves will remain relevantly dry. In the event that you do not have leaves to insulate the pots, you may substitute sawdust, straw, peat moss or shredded Styrofoam just as well.
Regardless of the method chosen to chill your bulbs, the bottom line is to use a method that will hold the bulbs as nearly as possible at 40° F and to not allow them to get above 50° F so that top growth does not begin until the chilling process has been completed.
During the chilling process make sure to keep the pots watered but not wet as rot will occur. During this process, roots will develop in preparation for future growth. This growth is essential for proper development and flowering later. Therefore, if you plan on chilling your bulbs outside, make sure you place them into cold storage at least three weeks before hard freezes occur to stop the growth.
There are some varieties that will be ready to be brought out of cold storage in ten to twelve weeks, but most will require up to 14 weeks. Once you start bringing your pots out of cold-storage, you can extend your blooming period over several weeks by removing your pots at one to two week intervals. Once removed from storage, it will require three to four weeks for the blooms to appear.
If you store your pots outside and they are frozen when you bring them indoors, store the pots at about 40° F. for a few days to thaw them slowly. But never touch the plant tops while they're frozen as damage can occur.
If the pots are not frozen when brought out of cold storage or after they thaw out completely, place them in a cool environment at a temperature as close to 60° F. as possible and out of direct sunlight until top growth begins. At that point you can move the pots to sunlight until the buds form, then move them back to bright light. Keep the bulbs watered but not wet and avoid fertilizing as it's not needed at this time.
Once the buds are fully developed, move them to the area where they will be displayed. Avoid sunlight, drafts and heat registers in order to prolong blooming. To further extend blooming, move the pots back into a cool area at night.
Bulbs that have been forced to bloom out of season are normally not saved and are normally discarded. However, if you cannot bear to part with them, continue to keep them watered and provide houseplant fertilizer or preferably bulb food at this time as directed on the container. Continue to do this until the tops die back normally. Them remove the bulbs and plant them in the garden as you normally would spring bulbs. However, it may be many years before the bulbs bloom again.
Tender bulbs, such as "Paperwhites" and "Amaryllis
" do not require cold treatment and bulbs such as the Paperwhites and Hyacinths are often grown in nothing but water and pebbles for support. Hyacinths are normally "planted" in glass containers that allow only their base to touch the water, while Narcissus are "planted" in dishes of gravel where the water comes approximately 1/4 of the way up the bulbs and are almost touching each other. For both of these bulbs, start them in September or October. Place Hyacinths in a cool location at 45° F to 50° F until tip growth begins and is 3" to 4" tall and the flower bud begins to emerge. Normally this will take from eight to twelve weeks, at which time you should move them to a bright location as with other potted bulbs outlined earlier. Bulbs grown in water should not be saved and should be discarded after blooming.
Amaryllis are normally grown in soil, one per pot, with approximately 1" between the bulb and the pot all around. Grow on a sunny window sill until buds form. At which time you will want to keep them in bright light, but no direct sun to prolong the flowering period. Once flowering ends, treat Amaryllis the same as other houseplants with regular watering and fertilization. More on Amaryllis in a later article.
