Our days are getting longer and warmer, and many gardens are awash in the color of spring-flowering bulbs like daffodils and tulips. Unfortunately, the flowers will eventually fade, leaving many of us wondering what we can do to make sure they’re ready to go again next year.
The most important thing you can do to help your bulbs is to leave the foliage on the plants. Leaves are necessary for plants to photosynthesize and produce the food the bulbs need to form flowers for next year. If the foliage is removed or mowed too early, it can result in a smaller, weaker bulb that will gradually decline and die out.
Leave the foliage on the plants until it begins to turn yellow and die back. It can then be removed, as it will no longer produce food. For smaller bulbs like snowdrops and squill this will happen relatively quickly. For larger plants, such as tulips and daffodils, it may take several weeks for the foliage to die back.
One problem with letting foliage stay is that it can become unsightly over time. In an effort to make their gardens neater, many people tie their foliage together to make it less conspicuous.
However, this is not recommended, as it will reduce the amount of light the leaves can absorb, thereby reducing the amount of photosynthesis, resulting in less energy being produced by the plant. As an alternative, you can intercrop annuals with your bulbs to help hide the foliage.
Although we don’t want to remove the leaves, it’s a good idea to remove spent flowers from plants to prevent seed pods from forming. If plants are allowed to produce seeds, this will use energy that could otherwise be used for bulbs and will often result in smaller bulbs.
Spring-flowering bulbs can be fertilized after they finish flowering. Look for a fertilizer high in phosphorus (middle number) and low in nitrogen (first number), such as a 5-10-5. Fertilizers are generally applied at the rate of 1 to 2 pounds per 100 square feet. Be sure to work gently or water it into the soil.
After several years, you may notice your bulbs producing smaller or fewer flowers. This often happens when they are crowded. Bulbs often reproduce by division, where new “daughter” bulbs form from the original “mother” bulb, causing plants to become crowded. If this happens, the bulbs can be dug up and divided once the foliage has died and the bulbs are dormant.
Carefully dig around the cluster of bulbs and lift it out of the ground. Separate the bulbs and discard any that are damaged or soft. The bulbs can then be replanted immediately, or they can be dried and stored in a cool place to be planted out in the fall.
Many gardeners who love spring bulbs are getting a head start on beauty by “forcing” the bulbs to bloom indoors earlier in the year. This is accomplished by simply exposing a spring-flowering bulb to an artificially warm environment much earlier than outdoors. Bulbs should also be exposed to a cold period before warmer temperatures to mimic the natural cycle that these plants experience in the wild. The cold period required varies by species, but generally takes about six weeks.
Although they are usually discarded, you can try planting potted bulbs that have been forced to bloom outdoors the following spring. Make sure they get plenty of sun and let the foliage die back naturally. The bulbs can then be planted once dormant or in the fall. The bulbs will probably only produce leaves the first year, then flower the second.
Ken Johnson is a Horticulture Educator with UI Extension, serving Calhoun, Cass, Greene, Morgan and Scott counties. This column also appears in the “Good Growing” blog at go.illinois.edu/GoodGrowing.
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