That's a bummer, man. Hope you can make it.
Look at it as an opportunity. It can be a good thing to get laid off if you take it as the kick in the ass to do what you wouldn't have done for yourself.
Get the landscaping thing going full blast. Spend your downtime marketing the crap out of your business, every chance you get. That will build up your business in a big way. Learn the marketing techniques you need. The info is out there.
If your former employer calls for help, say, "Sure!" Then, help them out, but before you help them, bill them IN ADVANCE for the work you do. In other words, charge them a retainer for an hourly rate. When the retainer is HALF gone, bill them for more retainer. Do more work. When the work is done, refund any overages they paid. Make sure your hourly rate is high enough to cover your self-employment taxes (about 18%), your health insurance (about 10% or more), your professional expertise, AND your profit on top of that. Usually, it's about 2.5 times what your prior hourly rate was but round up. If you were being paid $25/hour before, charge about $60 for your consulting services. Even at that rate, you WILL be saving them money, trust me on this.
Whatever you do, do NOT allow them to get time from you for which they have NOT paid you in advance. End of discussion, my friend.
Last but not least, if you have expertise in doing something like installing electronics in cop cars or whatever, realize that is VALUABLE. Start your own business doing this and take the business for yourself. This is a capitalist society and competition is the name of the game. You can do it cheaper and faster than the other guy, including your former employer.
Go for it!! You can do it and retain your self respect.
--Wag--