Why don’t tulips come back year after year in my garden?
Evelyn Lawrance, Eastham, MA
Keep bulbs under the radar of rodents by planting them 10 inches deep.
Photo/Illustration: Carol Ruzicka
Sydney Eddison, the author of several books on gardening and a former contributing editor, responds: A major reason that tulips fail to return year after year in the colder climates is because they are eaten by rodents. Unfortunately, the bulbs are as popular with mice and voles during the winter months as the flowers and foliage are with deer in the spring. One secret to longevity in tulips is in selecting firm, healthy bulbs in the first place and planting them deeper than is usually recommended.
I have found that the life span of tulips can be greatly increased by digging holes the depth of a shovel blade (about 10 inches) and covering the bulbs with about 8 inches of soil, instead of the customary 4 to 6 inches. Most mouse and vole runs are relatively shallow. It is hard to say if the deeper planting alone is protection against mice and voles, but it helps. Otherwise, tulips that have been planted 10 inches deep have survived in my garden for five years or more. Deep planting also extends the growing season by giving the bulbs more time to develop roots before cold weather sets in.
The most effective method of protecting the bulbs from rodents in the winter has proved to be planting groups of five or six in cages made of half-inch mesh hardware cloth with a bottom and four sides and open at the top. These cages, which are labor intensive to make and install, are not foolproof, however. In addition to tunneling, voles scamper across the surface of the soil and attack from above, sometimes leaving the cage empty. But the good news is that usually enough of the clumps survive to make an attractive spring show.
It is the nature of a tulip bulb to produce new bulblets at the base of the mother bulb every year. Eventually, the mother bulb dies, leaving the bulblets to grow into flowering size. Thus, as their numbers increase, the vigor of the bulbs declines, which is why tulips are often discarded after flowering and replaced by new bulbs in the fall. It takes skill and perfect conditions to propagate top-quality tulips from offsets and is best left to the professionals. A clump can last for a good many seasons in the garden, however, if you don’t mind a group of smaller flowers on stems of different heights. A five-year-old clump will not display uniformly large flowers on tall, sturdy stalks. But in a border, a looser effect can work well with the emerging foliage of the perennials.