“I bought my home last fall and was pleasantly surprised by lots of flowering bulbs this spring and would like some tips on how to best care for them and choose more to plant this fall. Can I cut back the ugly foliage now?”
— Tracy Patterson, Morton Grove
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Bulbs do not require much maintenance. They will generally perform best in a location that is moist in spring and fall, and dry in summer. Most bulbs will not perform well in beds that are consistently moist or watered heavily throughout the summer. An important consideration for being successful with bulbs, like other plants, is choosing ones that are well-suited to the growing conditions in your garden.
Plant daffodils and ornamental onions if you have rabbits and deer browsing in your garden. Tulips and crocuses are routinely eaten by deer and rabbits, but you can grow them by diligently spraying repellents in spring as they are growing. I have also seen plantings of crocus dug up by squirrels and chipmunks this spring as the foliage was going dormant.
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It is tempting to cut back the bulb foliage before it should be trimmed, as the weather warms and the foliage looks increasingly worse. It is best to wait until the bulb foliage has gone dormant before cutting it back. The leaves will turn yellow to brown. Once the leaves have all turned yellow, it is OK to cut them back. The bulbs need their leaves to photosynthesize and make food that is stored to produce foliage and flowers next year.
Cutting the foliage back too soon can reduce the vigor of the bulbs and flowering the next year. Tying up the leaves, bending them over and braiding the leaves are not good practices either as it reduces the leaf surface for photosynthesis. If you plant bulbs in the lawn, then you need to hold off on mowing the lawn in these areas to give the bulbs time to go dormant. You will probably need to cut the grass before the bulbs are completely dormant so set the mower at the highest setting to save as much of the bulb foliage as possible.
I generally do not fertilize my bulbs, though they end up getting fertilized when the shrubs and perennials planted around them do. Phosphorus is often recommended for bulbs, but this nutrient does not readily move through the soil, so surface applications of it will do little good for any of the plants in your garden. Many garden soils already have adequate levels of phosphorus for plants to perform well. Test your soil if you want to know for sure.
If an established patch of bulbs starts to bloom less or begins blooming sparsely, the bulbs may have become overcrowded, or the planting site too shady as adjacent trees have grown. That’s the signal to dig and divide or move them to another location.
The first step is to lift the bulbs from the ground, being careful to dig the bulbs and not pull them up by the foliage. Take care when digging that you don’t damage the bulbs themselves. Start digging a few inches away from the plants and wait until the bulbs are loosened up before trying to pull them up. The best time to move or divide bulbs is when the foliage has gone dormant, meaning the leaves have finished producing food for next year’s flowers and you can still see their location.
To divide bulbs, carefully pull the small bulbs from the base of the plant to increase plant numbers and gently separate them so that they can be planted with more spacing in their new location. The larger the small offset bulbs are, the sooner they will flower. Check the original bulb for firmness. If it appears in good health, go ahead and replant it; you may still get several years of flowering. If it appears shriveled or damaged, toss it.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.
