Q: I’d like some gladiolus in the garden. Is it too late to plant summer flowering bulbs now?
— John Davis,
A: After frost, mid-February into April is a good time to plant gladiolus in our county, as well as other summer-flowering bulbs like tuberous begonia, dahlia, calla lily, daylily, tuberose, and cannas.
If you have room, try groups of gladiolus planted at two-week intervals for a succession of bloom. The earlier you plant gladiolus, the more likely you are to avoid damage from thrips, a warm weather pest that dotes on glads.
Gladiolus prefer full sun, light, well-drained soil, and plenty of water during the summer. A layer of bone meal below soil at the bottom of the planting hole will provide nutrients.
By “summer-flowering bulbs,” gardeners usually mean plants that grow from thickened underground storage units, like corms (gladiolus), tubers (tuberous begonia and dahlia) as well as true bulbs (lily.) The above plants all flower in summer, but they differ in preferred growing conditions.
For example, fragrant tuberoses appreciate heat while tuberous begonias generally prefer cool shady gardens. Beautiful Asian and Regal lilies have the reputation of being difficult to grow. They like rich, consistently moist soil, so they often work best as container plants. On the other hand, day lilies (Hemerocallis) that grow from thickened roots are among the least-demanding of flowers in our climate.
In fall, gladiolus and dahlias are usually lifted and divided after foliage has yellowed. The corm or tuber that was planted originally has done its job, but several new tubers will surround the old dahlia tuber, and a new corm sits above the old gladiolus corm. (Joe Sabol, our resident expert for dahlias, recommends not lifting them since damage to the tuber is a higher risk of killing them than our temperatures on the Central Coast.) These can be stored and planted next spring.
Contact local Master Gardeners for more information on planting, growing, and storing conditions for “summer flowering bulbs.”