Q. When should I plant my tender annual bulbs?
A. It is safe to plant your tender bulbs after the average date of the last frost, which is approximately May 15 in the Chicago area. It is important not to work the soil while it is too wet. Soil should crumble when it is squeezed into a ball. If it doesn’t, then it is best to wait until it dries out a bit to avoid ruining the soil’s structure. Tubers of caladium, canna, dahlia, montbretia (Crocosmia), and tuberose will emerge approximately two weeks after planting. Set out stakes for tall dahlias before filling in the planting hole so you do not skewer the tubers. Consider planting gladiola bulbs in two-week intervals to have a continuous supply of blooms throughout the summer. Plant tuberous begonias that were started in a soilless compost earlier in the year in well-drained soil approximately two weeks after the frost-free date, some time in early June. Dormant tubers that were started in February should begin to bloom in June and those started in March or early April should bloom in July.