I put a whole pile in the planting hole as mine is augmented with aged chicken manure. It can also be used as mulch.

Linda

You can top dress with compost anytime you have compost to hand. It really doesn’t matter.

Remember that compost isn't a fertilizer, especially as a top dressing or mulch. It mainly helps the soil retain moisture by cutting down on evaporation. So if there is a time for letting your plants dry out, that's a great time not to apply it.

I also blend some compost into the planting holes, but the best time to apply compost as a mulch is after the soil has warmed up. If you're planting tomatoes outside now I would assume that you're located further south than me (Va)?

I'm in Hinesville, Georgia, zone 8b, Southeast Coastal Georgia. I usually wait till April to plant tomatoes, peppers and eggplant, but the weather has been so mild I thought I would try planting earlier than usual. Also, as this is my first year of retirement, I'm excited to be able to give the garden more attention than previous years. Where are you?

Central Virginia here where the soil and air temps are still too relatively cold to plant tomatoes outside (in fact I'm starting them from seed inside today). My tomato plants will be transplanted outside around early May at best and that's only if the long range forecast looks good and warm (nite time lows at 50F+). You may be ok now down there near the SE Georgia coast if the soil has warmed up enough, but keep an eye on the long range forecast, it's not an ideal outlook but it can give you some hint at what's immediately ahead.