Answer: Parsley can be picked any time. If you remove the larger outer leaves individually, the center will continue to grow. Or, you can cut it back hard all at once.
With basil, you can remove a few leaves to use any time. The plant should also be cut back periodically to encourage it to regrow more densely and to prevent it from flowering. Once it flowers the flavor usually turns bitter. And, as an annual, after flowering it usually declines.
Oregano can be treated the same as the basil. Use a few leaves whenever you wish, cut it back quite hard periodically to keep it growing dense and full. It too is better before it flowers. This is a perennial and should come back for you next year.
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