Mouse and Garden: April 9, 2006 Archive

Do we need a revamping of the USDA hardiness zone system for planting? Here in the Twin Cities we are at zone 4a. That means we can buy any plant that is zone 4 and it will do well here, right?

Not exactly. The zone system only measures minimum temperatures – the coldest temperature at which a plant will make it through the winter. The zone doesnt take into account the freezing and thawing cycle, the length of the growing season, humidity, or rainfall.

I grew up in the state of Washington and out there on the west coast they use a system set up by Sunset magazine 40 years ago which consists of 24 zones that take into account the factors that I mentioned above. It made things easier for my family in the semi-arid region south of Yakima to realize we couldn't grow the same things as in wet Seattle.

We really need something like this for the Midwest. Minnesota doesn't have as drastic climatic regions as Washington, but we do have a shorter growing season than most of the country. Just because a zone 4 plant does well somewhere else in the US doesn't mean that it will do well here. Any flowering tree opening before May 15 is in danger. Any fruit not ripening before October 1 probably won't make it. That means if a zone 4 tree says it takes more than 150 days for the fruit to reach maturity, you will need to do some fancy footwork to get a harvest.

I have wanted to try out the sungold and moongold apricots developed by the University of Minnesota, but the problem with them is the tendency to bloom before our last frost. I will have to weigh my stress tolerance versus my pride of being the only one on the block with apricots for that purchase.