Alliums like fertile but well drained soil. I don't tend to pay attention to the acidity because if the garden is well composted, rather than native soil, it will be close to neutral anyhow. Mainly, onions and garlic do not like *competition*. Garlic is easier in this way than onions and I, a lazy gardener, have never produced onions that were worth the effort and they are so cheap, I just buy them. So, even watering (their roots are shallow, so deep watering isn't ideal) .
Re: fertilizer. Hmmm. We plant out our garlic in August to harvest the following year. I'm not experienced enough to know whether spring planting gets you garlic bulbs in the late summer, but if they end up the same, I would let up on the fertilizing once they get full height at the latest. Maybe someone else has more experience with this. For garlic, snapping off the flower ends will get you the big bulbs. I tried not doing it this year, just to see, and they were pretty diminished compared to the year before. Snapping off garlic tops is something kids might enjoy, and they fetch top dollar at the farmer's market for stir fries.
Keep the patches well weeded (I need to say this because I don't keep anything well-weeded!). Good luck! Garlic is pretty easy, it's the onions I need to figure out. Maybe. Real estate in the garden is at a premium, and I don't have time for prima donnas, if that's what they want to be.
Edited by SweetSilver - 5/17/12 at 7:47am