They say to hill up fennel o keep the bulb white. What is wrong with its normal color if you do not cover it?

Exposure to sun can cause changes in taste and texture, in addition to color. It could be more fibrous and not as sweet.

If you're growing Florence fennel (the kind grown for the large white bulb), good luck! I had trouble getting much of a bulb at all - never mind if it was white or not. It's rather slow to grow and will bolt in hot weather. Doesn't like drought stress or overwatering either. And it's said to leave chemicals in the soil which will retard the growth of subsequent plantings (seems to have inhibited my spinach and dill this year, but not the tomatoes, cukes or okra which are in the same bed).

I planted Florence Fennel last year and the bulbs were kind of fibrous. Not worth the effort to me, I love fennel seeds but was not impressed with the bulb.

I thought fennel was like leeks and celery, you have to hill it up or otherwise cover the base of the shoots or the root bulb won't blanch...blanch, that's the technical term for turning the bulb or stalk white. The chlorophyll can't do any good down in the dark, so it flees upward to the parts of the plant that are in the light.

Celery, as you probably know, is stringier and more fibrous as you get closer to the leafy tops of the stalks, and sweeter, crisper near the root and the heart.

I haven't grown fennel because I have not had much occasion to use it, but I assume it's blanching habits are like celery and leeks.

I grow fennel simply for the beneficial insects it attracts (a few plants scattered here and there throughout the other vegetables). Between that and the bluebird house at the edge of the garden (bluebird parents hunt constantly for insects and larvae when they have hungry mouths to feed, and they raise up to 3 "litters" per season), my pest problems are usually minimal. Of course that doesn't take into account this years escalating rabbit population. . .

Thanks for the help.

Too bad about fennel. I was going to grow it to try and get an easy to grow celery replacement. Will keep searching.