I HAVE THE SAME QUESTION AND WANNA KNOW.
THANKS FOR POSTING.

CYRUS

I've never tried growing Walla Walla, but here are a few tips I've found:

~ Walla Walla (as you probably know) is a long-day onion -- it wants a lot of daylight, so is best grown in Northern climates. You also need to plant early, of course. Are you planting soon enough?

~ Walla Walla likes a soil pH of 6 to 7. Have you checked your soil for acidity?

~ They also need a good deal of space -- are yours crowded? I read: 5 to 6 inches between sets and rows spaced 15" apart.

~ Also, a 10-10-10 fertilizer is recommended at planting, as you've done. But, about a month after planting, they recommend a high nitrogen fertilizer (21-0-0) applied at a rate of one cup for every 20 feet. Repeat every 3 to 4 weeks. And water immediately after applying fertilizer.

I've never tried Walla Wallas because my garden is always far too muddy in the spring to plant as early as these need to get in the ground. Heck, my garden is usually still covered with snow when most people are talking about planting long day onions.

I hope some of the above is useful!

Personally, I would fertilize every 2 to 3 weeks. I do mine every 18 days (I write it on my calendar or I would forget). Onions also love water. I've read blogs from people who grow onions for show and they really water their onions. I'm not sure how much is too, much but I make sure mine don't get too dry.

Good luck!
Catherine