I haven't grown Copra for a few years nor have I tried Patterson. Copra never grew very large in my garden and really didn't seem to store much longer than other types but I'm sure that was my storage conditions are not ideal.

The last few years I've just been growing Candy, Red Candy, and Superstar. I get my Dixondale bunches locally and they usually carry about 10 varieties but haven't had any Copra for a few years. They have had Patterson for the last couple years though.

I put last years Copra that softened in the spring into the ground and have a few seeds. It's too late to plant them this fall so I'll find a space for them next spring and hopefully will have some late onions that will store longer. Never tried this before.

I don't see the advantage of the Patterson variety as I like a range of sizes to match what a meal needs. The problem would be if Copra got too many onions that were too small to use, but I've never seen that.

I'd prefer the Copra's over Patterson but what can you do. I used the last of my Copra seeds in the 2020 season and those onions kept well into late summer of 2021. I diced and freeze dried what what left but I also grew Patterson last year also. Copra's tasted better IMO.

This year I planted a dozen Copra's for seed to collect. I don't know what I'll get next year from the seeds but I'm going to find out. What pisses me off is the retailers allow seed companies to put short day onion seeds in their displays in the northern growing zones. Like grande 1015 and other short day varieties which won't produce much of an onion in Minnesota. What pisses me off is those with little knowledge about onions don't have much of a chance and will lose interest in growing them.

I grow about 300 Copras each year and they average 3-4". They last 6-8 months in my cellar, and over a year in the refrigerator. I also grow 50 Candy each year for earliness and canning. The Patterson are supposed to last as long as Copra and are of a similar size. Worth a try.

I fully agree about retailers putting out seeds and plants that are not appropriate for the region! I also see short day varieties here in Zone 6a, and warm season seedlings like tomatoes and peppers for sale in early April, a good six weeks before the last frost date. I can only imagine how many people get disappointed and discouraged when these crops fail. Not sure who is more at fault, the growers, distributors, or retailers, but someone is either ignorant or profit trumps customer satisfaction. You would think growers and perhaps distributors would know better.