My carrots and onions (leeks, chard and spinach) are so small that I am needing to handweed. No chance of getting a hoe in as I will destroy the crop as well!
I started weeding last saturday after being away for a week, I went back on Mon and the weeds that I had left were bigger - and much much easier to pull up, it really made a difference. So if you can wait for them to be about an inch tall, then tehy are easier to hand weed, and the whole plant seems to come up, not just pull the top off! I have the weeds with teh little blue flowers, can't remember what its called now! Although also have some nasties that I am trying to remove (bindweed, a dandelion/thistle (mum calls cow thistle), housetails) all the time and will not let get any bigger!