All About Flower Bulbs

When tulips, daffodils and lilies burst into bloom, you’re probably not thinking much about the part of the plant that’s underground: the bulb. Flower bulbs are actually a type of food storage organ, a way that plants stash their homemade nosh to help fuel future growth and flowers. Many plants get lumped under the heading bulbs, including tubers, corms and rhizomes. Knowing a little about different types of bulbs can help you understand how these plants grow —and how you should handle them at planting time.

If you cook at all, you’re probably familiar with the internal structures of an onion. Guess what? Onions are what’s known as true bulbs, tulips are also true bulbs. A true bulb has layers of fleshy tissue that act as the food storage organ. Roots form at the base of the bulb and serve to anchor the bulb in soil and absorb water and nutrients. When you buy bulbs, you’ll often see dried root remnants at the base of the bulb. Examples of true bulbs: onion, garlic, allium, daffodil, tulip, amaryllis, grape hyacinth, Dutch hyacinth, Dutch iris, scilla, lily.

Inside a true bulb is a central shoot that contains layers of leaves and immature flowers. With bulbs planted in your garden, this central shoot forms after flowers fade. This is why it’s important to let leaves of bulbs like tulips and daffodils remain and stay green until they naturally die back. As long as leaves are green, they’re helping to store food that helps form the shoot for next year’s show. Most true bulbs have a protective papery skin (think onion, daffodil, tulip). An exception to this rule are the lilies, including Asiatic and Oriental types.

Lily bulbs lack an outer protective, papery layer. They’re often sold packed in sawdust or peat moss. It’s important to store lily bulbs correctly prior to planting because they have no outer layer that helps protect against moisture loss or temperature fluctuations. Keep lily bulbs cool (below 45 degrees F) but not freezing to help prevent sprouting. If sprouts form prior to planting, handle bulbs carefully. If you break the sprout, the lily won’t flower that year.