I went out to dig the other 20% of the sweet potatoes Tuesday morning and came home with this measly wheelbarrow full.  And for the rest of the day, I pondered why Monday's beds yielded up dozens of mammoth tubers while Tuesday's beds gave me just a few skinny roots.

I considered planting date, since I put in a bed every week or so between mid May and late June, but my measly beds were planted near the beginning of that succession and even the latest-planted bed yielded up good-sized tubers.  Or maybe it was the type of fertilizer?  Nope, I gave all of our sweet potatoes the same chicken manure compost.

I had just read Steve Solomon's Gardening When it Counts when planting our sweet potatoes this year, so I spaced the slips nearly twice as far apart as last year (only four slips in an average sized bed.)  That planting method might explain why I had so many huge tubers, but since I used the same method on the measly beds, it doesn't explain the disproportionate yield between beds.

Finally, the simplest answer came to me --- location.  All of my hefty tubers came from the upper garden where we enjoy a slightly clayey loam, while the measly tubers came from the mule garden which is pure clay.  I was tricked into thinking the mule garden would be okay for sweet potatoes since I've had good harvests from garlic, white potatoes, and carrots there, but my failure with onions in the mule garden clay and with all of the above in the back garden's even more clayey clay should have clued me in --- root crops just don't like clay.  Next year, I'll stick to the front garden for our sweet potatoes.

Check out my previous posts to learn more about when to harvest sweet potatoes and how to cure sweet potatoes.  Or, if you're really into planning ahead for next year, learn to make your own sweet potato slips!