Interesting questions.

I only mulch when an extended period of sub-freezing weather, without snow cover, threatens.

I fertilize before planting, again in late March/early April as growth really begins to kick in, and again in mid May(onions only). I also fertilize the bulbing onions more heavily than the garlic or multiplier onions.

I would recommend removing the winter weeds. If yours are anything like the winter annual mustards, grasses, and filaree we have here, then they will be a serious source of competition long before they die out in early summer. I have some spinach interplanted with one row of garlic and I think I can already see some diminished vigor in the garlic in that row compared to the clean rows.

This only my third season to be serious about growing garlic and onions, so I'm no expert and looking forward to seeing others responses to your questions.

I just fertilized my early varieties. I mulch as a way to fertilize, mixing granular fertilizer and/or chicken manure into composted wood waste. Of course, I enrich the medium in my beds before planting.

Here in NoCal it is early spring and the right time to feed whether or not we still have freezing temps ahead. Last year health issues prevented me from fertilizing and I could really see the difference.

I have been removing weeds all along, but still have grass and sheep sorrel popping up here and there.

The OP and I are in very different climates but i'm going to offer my thoughts anyway, maybe some if it will apply.
Mulching is great to reduce weeds, retain moisture when the heat finally comes and offer some time release fertility if your choice of mulch has any to offer.
My alliums get manure compost before planting and I find that it's enough for the garlic to go full season. I usually mulch the garlic with oat straw but this year I used washed manure from the local organic dairy (weed free!!).

Onions are a bit trickier. Their roots are shallow and fertility seems to wash away from them over the winter. We also have long wet springs here in Oregon and so I tend to hold off on mulch until late March. I use a compost I make which is mostly manure based and once I give them a good weeding, it gets applied for spring weed control as well as fertility.
Overwintering onions here finish up by June and garlic by the first week of July.
-Mark

Mark,

Thanks for the heads up about mulching. These forums are great for learning new techniques and stimulating thinking about things in a new way.

I spent an hour or so online looking for information about mulching garlic. I don't think I've hardly ever seen a practice so universally recommended-home gardeners and commercial growers from Ontario and Virginia to Texas and Oregon. I even found a study done by Colorado State University showing that unmulched garlic had a statistically significant lower yield than the mulched.

So, tomorrow afternoon, since I have some clean straw mulch available, I will enjoy the bright sunshine and 60 degree temperatures and mulch the bed with the garlic, overwintering onions, multiplier onions and spinach. I will also hope it doesn't blow away in Monday's forecast wind and dust storm.

Wertech, I have spread a light sprinkle of chopped leaves around my garlic & onions(multipliers)just to keep the next hard freeze off them(if we have one).
In places you can see the soil in the bed.
I will fertilize in late March, unless one of you more Knowledgeable gardener tell me other wise.
It is raining here at this time.

Beautiful day yesterday! In the 70's, I weeded and spread a thin layer of straw over them. I'll hold off on fertilizing, thanks!