Train your foremen. I think it bad form to have lunch on someone's lawn. Encourage guys to bring a thermos of coffee, or something cold along with nibbles. If you are going to be there all day, then, have a short break at the truck, not on their yard. Having them bring their own lunch I think is better. The lunch period doesn't tend to stretch. But foremen should have the ability to say, "It's f*((( cold out here. Let's find a warm place to eat.
Hire more guys than you need. Be up front and tell them that you got a bad batch last year, that you are deliberately hiring extra guys, becuase you expect that 1/2 of them won't make it. The first week is going to be a scramble if you don't have foremen.
Indeed, if you don't have foremen, pick out some of the guys who you think will do well at that level, and make a two day training course. In fact, pay your foremen for one evening a week initially for more training. During that evening, you drive to sites, and point out things that were done really well, or weren't that hot. Never mention names. Never chew a guy out in front of the others. This is how you set the standard for what is to be done.
If you have a problem with one foreman, don't talk to him at the meeting. Catch him as his crew comes in, and talk privately.
Build enough slack into the system that you can fire a bunch of guys, and not have everyone esle working infinite overtime. This is where you want a bunch of guys who are willing to work part time. The part can be small or large. If you do commercial garden work, you can find lots of people who have kids who want to work school hours only.
This can also help around the feast or famine. Here, a lawn has to be mowed twice a week from mid May to the end of June to look good. By August it only needs to be done every two weeks.
During the short times, give guys the option to either work short days, or fewer days. Organize that by crews.