Plants grow well in St. Paul, Minnesota because the soil is rich and the weather is just right but even rich soil needs to be enriched every year. You can create a organic compost pile that will help you enrich your garden organically with compost that you make yourself.
Set up a bin with organic wood boards or a metal wire fence so the compost is held in place while it is composting. You can make four boards into a square or you can curl metal fence until it is in a circle for a bin. The bin should be at least two feet wide. Put only organic material in your compost bin like leaves from an organic yard, old plants from an organic garden and left over food that is organic.
Let it all sit and compost for a year adding more when you get it and turn it at least once a month. If your organic material is dry you should put water on it so it can compost correctly. When you put the compost on your garden use the best composted part and leave the rest to compost longer for next year.
The material you put in your compost is important. It should be organic and you should not add anything that is not organic like artificial enzymes.