Should I grow Florence fennel from seeds or the bulb?
It grows only from seed; the so-called bulb consists of overlapping leaves that are not a true bulb. Best months to plant the seed are February, March and April, for harvesting in three or four months - seeds planted now tend to bolt in summer before the bulbous base is formed, though they can be cut back and left for winter harvest. Florence fennel is a perennial usually treated as an annual since the stems become more fibrous with age.
If I plant store-bought yams, will they multiply?
Hopefully. Sprout them first in the same way as seed potatoes. Once sprouts are 5cm tall and frosts have finished, plant 8cm deep in well-dug soil enriched with compost and rotted manure. When shoots push through, earth them up in the same way as potatoes. Tubers don't swell until late autumn, and you can dig them when the plants are cut by frost. What we call yams are known as oca in some countries; note that they are a species of oxalis.
If you have a gardening question, email Glenys at email@example.com