Answer: Three year old crowns should produce some edible spears. Try to leave more spears than you harvest. The remaining spears will produce foliage which will help feed the crowns. The second year there will be more spears to harvest. Eventually you'll be able to harvest over a long season.
Mulch the bed after you've finished harvesting with a 4-6" layer of compost. This will bury annual weed seeds and make it hard for perennials to grow. You'll still have to weed, but hopefully it'll be less of a chore.
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