Mulch after the soil has had a good chance to heat up --- I give it 2 weeks + of summer weather. Around here usually means early to mid June.

The idea is that the mulch (particularly one like straw) acts as an insulator -- put it on before the soil heats up and you're keeping the cold in, put it on after it's heated up and you're trapping the heat in and reducing extreme fluctuations. It's also, of course, reducing weeds, trapping moisture and preventing soil from splashing on the plant and spreading disease. All good stuff.

Straw is an effective mulch. The only issue I've heard is that a lot of straw has weed seeds in it, so you may be introducing a lot of weeds to your garden.

I apply my hay mulch immediately after planting, and right up to the stem to keep the leaves off the ground and prevent splash back. I don't put the plants out until the soil is reasonably warm. Worked for me for 35 years.

TomNJ

I planted out 4/15 and put wheat straw out 5/15, after putting out one section of newspaper (open and cut in the middle for stem of plant. over lap paper to make a solid line of paper,if not lay a section between each plant. you want a solid row of paper,it holds moisture in and keeps weeds and grass out. In the fall I pull plants (take out of garden) and til in paper and WHEAT STRAW. Wheat is better than hay (no grass and weed seed) good luck Bill

Thanks for the good advice folks.

Straw is a real good choice I have been mulching as I plant today it is hot and dry right now soil is plenty warm already and I feel the benefit of even moister is well worth it

Other years will vary though

The weeds and grass you get from hay and straw mulch are so very easy to get rid of or pull it is really not worth going to any extremes to get a special kind of straw use what ever is available locally