I've been giving my plants equal amounts of npk so they can continue to put on growth, and keep flowering at the same time. This genus Stachytarpheta is a new one for me. I love Verbenas and try to grow as many hummingbird plants as possible. Did you buy your plants, or grow them from seed? How many years have you been growing porterweeds? They're more of a tropical plant, perhaps they require putting on a lot of growth before flowering.

Jay, most of my plants I purchased, either online or from a local vendor. Many, however, now come from cuttings. They are very easy to grow from cuttings. Perhaps one or two have come from seeds.

I purchased something like a dozen this year from Almost Eden. They began blooming pretty much right away after I put them in the ground--but I gave them a heavy dose of Flowertone when I planted them. I can't find any 10-10-10 in a time-release fertilizer. Flowertone is organic and, I believe, fairly quickly breaks down.

Tom, I'm in zone 6a, so up here porterweeds probably aren't hardy, and would have to be treated as annuals I'm thinking. Going to look into it. I'm no expert in fertilizing. I'm just doing what I think makes sense. I hope your plants do have loads of blooms. There is still plenty of growing season left. Edit.... Tom porterweed is hardy in zone 10 and higher. Questionably hardy in zoned 9a/9b. I'd consider growing it as an annual if it was sure to flower. If I only had a greenhouse :( They are supposed to be the all time best nectar producers.

How tall are your porterweeds, Tom? According to what I've read, when they get tall and woody, they bloom very little.

Sherry

Jay, I think the closest to them in your zone is the buddleia. They may be perennials where you live. I can't grow them here because the nematodes eat their roots. The porterweeds are clearly annuals for you. Still, they are terrific nectar plants and I would consider trying to overwinter some inside in your growing zone.

Sherry, I had some that had grown to about ten feet tall and they had been blooming nicely. Unfortunately, they were killed off in the hard freezes we had last winter. The smaller, younger ones have mostly come back.

I looked at the info on Flower tone and Espoma recommends reapplying it once a month during the growing season. I have never had to do this before, but I am doing it now. Hopefully they will start throwing out lots of blooms soon.

Tom, with regard to the rains, I can say that my porterweeds have been
flowering more, not less.
Even a bit of flowering by plants that have been in a bin of water
for 8 months