Forcing Bulbs

Mary Ann Ryan
Adams County Master Gardener

(9/2) September brings boxes and bags of fall bulbs into the garden centers and super stores. Tulips, daffodils, crocus and other bulbs will be found on the shelves. These bulbs are best planted in the garden September through November for best success. But did you ever wonder how to have those spring bulbs bloom indoors in the winter? It may seem a bit early to think about it, but now is the time to prepare bulbs for forcing indoors. Gardeners and non-gardeners can enjoy spring even in the middle of winter by forcing bulbs.

First, determine what to force. Tulips, daffodils, hyacinths, dwarf iris, crocus and grape hyacinths are great for forcing. Twelve to eighteen weeks of chilling are needed to force most bulbs. Count back from the month the bulbs are needed to bloom. If February is the month, that makes it around Oct. 1 when those bulbs should start its "chill" period.

Choose your bulbs. They should be firm, not soft or moldy. Pick out the biggest bulbs, as they will have the best chance of blooming. When choosing what kind of bulbs, think about fragrance as well as color and shape. In a warm home, the fragrance can be more powerful than when its outside. I love the smell of hyacinths, but not everyone does.

Select the container. Often 6", 8" or 10" plastic pots are used, depending on the sizes of the bulbs. The plastic pots keep them light in weight for cooling in the refrigerator. Then when the bulbs begin to sprout, they can be set into more decorative containers. The container must have holes in the bottom for drainage. If the soil falls out while filling the container, put pieces of a broken clay pot over the hole, or pebbles, or even newspaper to hold the soil in, but allow water out.

The soil should be well drained. Regular potting soil will work fine. Again, drainage is very important. Be sure to choose something that houseplants could live in.

Fill the container about ½ full. Place the bulbs in the container close together. It will be a better display of color the more bulbs placed in the pot. Typically, 5 or 7 tulip or daffodil bulbs can fit in a container, depending on the size. Hyacinth bulbs are a bit bigger in size, so maybe 3 – 5 bulbs in a container would suffice. Smaller bulbs, like crocus, iris and grape hyacinths can take a smaller container. Seven bulbs will give a nice display. The smaller the bulb, place closer to the surface of the soil.

After placing the bulbs in the container, fill it the rest of the way with the potting mix. Water it well, till water runs out the bottom of the pot. Then chill. This step can be done in a refrigerator – where apples are not stored – for 12 – 18 weeks at 35 – 45 degrees.

Another way to provide the chilled period is to put the pots of bulbs in a cold frame or against the foundation of the house, completely covered with mulch, straw, or compost. This will keep the temperatures more even, so the fluctuation in temperature doesn’t rot the bulbs.

Even though the bulbs appear to be dormant, the root system is growing, therefore, watering is essential. Keep the soil moist, but not wet. Close to the time to put the bulbs on display, roots may be coming out of the bottom of the pot, and/or the bulbs may begin to grow. This is the best indication that they are ready for display. If the leaves are yellow or pale in color, that’s ok. they are just in need of some sunlight. When put in a window, those leaves will green up quite quickly.

There is also layering of bulbs that can be done. It’s the same concept, but using a large pot, and putting the bigger bulbs on the bottom and working up the container till the smallest bulbs are at the top. Management of something large is done the same way as the smaller, individual containers, but most easily managed outdoors, as opposed to a refrigerator.

Just to make things more complicated, as the holiday season approaches, you may find fall bulbs in packaging that says something like "just add water and watch them bloom". These fall bulbs have been "pre-chilled" so you don’t have to go through all the steps as above.

In addition to fall bulbs, paperwhites are seasonal bulbs that do not require as much work. These bulbs truly are "plant, water and watch them bloom" type bulbs. Paperwhites are different from other fall bulbs in that they are not hardy. Planting them outdoors after blooming will not bring flowers the following year. These should be thought of as temporary color in the house. The most common variety of a paperwhite is ‘Zeva’. Although there are other varieties, some double, some yellow that can be found in the nurseries or on-line, all are treated the same way.

Paperwhites can be put in soil or in pebbles. When planting in soil, fill the container with potting soil. Nestle the bulbs on top, so that about ¾ of the bulb is underground, the other quarter is above the soil level. Water well; put in a sunny window and watch them grow and bloom.

If using pebbles, use a shallow container with no holes, fill with pebbles, and nestle the bulbs on the surface, placing them just deep enough that the bulbs are supported by the pebbles. Put a bit of water in the container, just till it hits the bottom of the bulb. Often glass containers are used for this purpose so the water level is easy to monitor. Paperwhites can need staked and tied to keep the flowers from flopping over.

Consider forcing bulbs this winter. Whatever kind or method you choose, give it a try and enjoy a brightness of color in the dark of winter!

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