ELi ON EARTH: Bulbs

While the chill in the air and the leaves on the ground may signal the coming of winter, they also mark the time in East Lansing for planting many kind of bulbs. For plants that form them, bulbs are both the food storage and growth structures for spring.

Although they grow in the ground, bulbs are not roots. If you look carefully at bulbs (including heads of garlic or onions), you will see thin root threads at the bottom of the bulbs. The bulb that sits just above the roots is really a part of the stem of the plant, and the fleshy layers of the bulb (e.g., the layers of an onion) are leaves of the plant modified for storing nutrients.

There are other plants that store nutrients in their roots, like turnips and carrots, but those roots are not bulbs. Likewise, the rhizomes of irises, ginger, and poplar trees are root stems and not bulbs, although, like bulbs, you can successfully plant rhizomes and they often store nutrients for the plant.

The life cycle of plants that form bulbs depends on their natural habitat. Many bulbs, like tulips and daffodils, come from areas with dry, hot summers and cold, dry winters. For these plants, their dormant period starts in summer after their foliage dies back and dormancy stretches until the first warm, wet days of spring. Bulb plants from wet areas of Michigan, such as trillium, have similar cycles, but others, such as native lilies, which need less water, have longer leafy periods and are only dormant as bulbs in the winter.

While bulbs are the “dormant” stage of their plants, they are not just “asleep.” Soon after planting, the bulb sends out roots from its base to collect water and nutrients. As spring approaches the central bud begins to grow up through the center of the bulb. (Think of that little green shoot that sometimes appears out of the end of a bulb of garlic or out of an onion.) The growing bud matures and emerges from the center of the bulb as a stem and pushes through the dirt toward the surface. All through this period, the plant uses the stored nutrients of the bulb to power its growth and development.

Most people are familiar with the above-ground cycle of bulb-forming plants. The central stem and leaves grow up through the ground before forming a flower. If you dig up the plant during this leafy period, the bulb is clearly a part of the leaves and stem of the plant.

Bulb-forming plants can reproduce sexually through their flowers, but they can also reproduce asexually by dividing their bulbs or forming bulblets (little bulbs at the base of leaves or at the crown of the plant). After flowering, bulb plants have a prolonged foliage period during which the leaves gather and send nutrients to the bulb. If all goes well, there are enough nutrients to divide the “leaves” at the base into new bulbs. The result of this process is pretty easy to see in a head of garlic. The new bulbs are arranged around the central stem, which was the original bulb. Naturalizing ornamental bulbs (including some daffodils and “species tulips”) reproduce this way, but bulbs that do not naturalize (including hybrid tulips) put their nutrients back into the original bulb and do not divide.

Not only are bulb plants ornamentally useful and attractive, there are many native and edible species for East Lansing-area gardeners to enjoy. While onions for eating are planted in the spring, most ornamental bulbs and garlic should be planted in East Lansing from September through November. It’s not too late. Planting garlic in the late fall is a remarkably easy experience—just divide up a head of garlic and plant the cloves 2-3 inches down in good soil in a sunny spot. Next year you’ll get to enjoy fresh scapes as well as juicy fresh garlic.

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