small anise
by Mark C.
(Boston , MA)
Doug says - Mark, let's assume you haven't misidentified the plant. Anise (herb) is Pimpinella anisum and it has tall thin stalks, with feathery foliage. Sweet Anise or Fennel (Foeniculum vulgare) is the plant that produces a bulb.
And not knowing how you are growing them - it's really difficult to tell you what to change.
Full hot sun. Anything less produces lanky stems.
Long growing season. Shorter than hot and long produces small bulbs (remember this is a Mediterranean plant) A Boston climate may not be optimum.
Medium fertility and no water shortages. Don't overfeed or overwater.
Hope that helps