Although short-lived, tulips (Tulipa spp.) provide a dependable burst of color for several weeks each spring. These perennial bulbs, which grow in U.S. Department of Agriculture plant hardiness zones 3 through 9, produce broad green leaves that fuel the flowers. The foliage needs to be trimmed after the tulips flower, but you must do it at the right time and using the correct method to ensure your tulips continue to bloom each year.
The leaves of the tulip plant collect energy from the sun, which the tulip stores in its bulb. This energy, along with the nutrients collected by the roots, fuel growth and flowering in the following year. The leaves must remain on the tulip for their entire life cycle to ensure they collect the maximum amount of energy, otherwise the tulip may fail to flower the following spring, or the bulb may weaken and die.
Tulip flowers fade about six weeks before the foliage dies back. The old flower will attempt to form a seed, which uses up nutrients and expends the energy stored in the bulb. Deadheading the tulip removes the old flower so it can't set seed. This doesn't damage the living foliage. Cut off the entire flower head just below the swollen tip after the petals begin to fall off. Leave the stem and foliage in place to continue collecting energy.
The leaves usually begin to yellow about six weeks after the last bloom wilts. You can trim the old leaves from the bulb at any time after they begin to yellow. The simplest method is to cut the leaves off the plant at soil level, but take care not to cut into the neck of the bulb. For large tulip beds, you can use a lawnmower to cut down the foliage. Set the mower 2 inches so you don't cut into the bulbs. Avoid pulling on the leaves, because this will pull up the entire tulip bulb.
After you've removed the foliage, you won't know where your tulip bulbs are. If you are digging the bulbs up that fall for division, mark their locations with plant stakes before you cut down the foliage. Also mark where the bulbs are so you don't disturb them when planting summer annuals. The dead foliage can harbor pests or diseases or pests, so dispose of or compost all the removed foliage promptly.
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