I've tried making refrigerator pickles twice and they both seemed to have this strange sweetness that I'm really not digging. I like really garlicky Kosher dills from Claussen or half sours from the Pickle Guys or Gus' Pickles (in NY). The recipes I used always called for dill seed – but I can't seem to find seeds in any grocery store near me. So I used fresh dill in both times and I think that is what is giving me that strange sweetness. Could I be right? Will dill seed make that much of a difference?
For what it's worth, the second batch came closer to the taste I wanted (minus that weird sweetness): Vinegar, water, salt, lots of garlic cloves, pepper corn, dash of hot pepper flakes, fresh dill
If you do try to grow some dill herb, in a small patch of garden or in a window box, don’t plant the seed all at once. In her recipes in The Joy of Pickling, Linda Ziedrich is a big believer in using fresh herbs, even suggesting that it’s worth trying to grow some dill yourself, staggering the planting every few weeks until midsummer so that you have a constant supply as it matures. She says that fresh dill seeds taste very different; that they “taste fresh and mild” before they dry out.  Ziedrich, Linda. The Joy of Pickling. Page 14.
In real life, outside of coffee-table beautiful home canning books, some gardeners may find that their cucumbers are ready before their dill weed is.
Other canners will find that their store has a deal on cucumbers but there’s no fresh dill weed within miles to be found.
Or it’s the dead of winter, you are doing winter canning with imported cucumbers (despite the very remote odds of getting a crisp pickle with them), and the balcony where you grow your herbs in the summer has howling winds from Siberia whistling through it off of Lake Michigan.
So, you need to substitute some dried dill for the fresh. Purists may say “perish the thought”, but here’s some tips on how:
Linda Ziedrich says that if a recipe calls for a fresh dill umbel and you don’t have one, use one teaspoon of dried dill seed instead.  Ziedrich, Linda. The Joy of Pickling. Boston, Massachusetts: The Harvard Common Press. 2009. Page 14.
(Note: an umbel is a whorl, a round circle spray of the plants buds or flowers.)
The National Center for Home Food Preservation says, “For each quart, try 3 heads of fresh dill or 1 to 2 tablespoons dill seed (dill weed = 2 tablespoons).”  National Center for Home Food Preservation. Frequently Asked Pickle Questions. Accessed March 2015. [Ed: It’s not clear what they mean by the dill weed = addition at the end there: perhaps it means OR 2 tbsp dill weed. ]
For a 3-5″ (8 to 12 cm ) sprig of fresh dill, you can substitute ¼ teaspoon of dried dill weed.