About how much earlier can a plant be started in a greenhouse?

[michael68]

I'm at 34 N, 3,000ft elevation. (about 915m)

What's the earliest I can start some seeds in pots, is mid April fine?

We got plenty of sunlight here around that time, but in mid April we can still get light frosts and chilly nights up until May or so.

I just want a fairly small portable one, any tips for keeping the seedlings warmer, like should the pots be lifted off the ground, etc?

 

[Littleleaf]

Some cheep was to keep them warm.

Large black trash cans filled with water.

stacks of tires filled with soil or buckets filled with water in the tires.

a fresh compost pile will generate lots of heat.