It is common for certain spring flowering bulbs to have some foliage growth in the fall. The following is more information.
Some bulbs tend to come up in the fall -- grape hyacinths are a good example. Customers may become concerned that there is something wrong and that the bulbs won’t bloom in the spring. Spring-flowering bulbs have hardy foliage and will not suffer much foliage damage by coming up in the fall. Their flowers won’t come up until spring and will bloom normally. It might be a good idea to cover emerged foliage with a light layer of leaf mulch.
Grape hyacinth foliage dies back following flowering in the early summer, but grows actively again starting in mid-fall. The foliage will persist through the winter. Depending on how severe the winter conditions are and how much protection it receives from snow cover, it may be an attractive element in the winter landscape right up to the time that new growth begins in spring.
Grape Hyacinth in late November. Photo from the Plant & Pest Digital Library at Purdue University.
Information from the Ornamentals Hotline Newsletter from UD Cooperative Extension and Mike Dana, Department of Horticulture and Landscape Architecture, Purdue University.