1/2 teaspoon per gallon will give you 125ppm nitrogen, which is what many people aim for. That would also be considered a full strength dose by most fertilizer instructions. I don't recommend high phosphorus fertilizers like your 19-31-17, but I doubt it would hurt anything as long as you flush the plant thoroughly when watering.

Thanks, penfold2. Since you're a member of this forum, I'd be interested in knowing your recommended fertilizer, esp the numbers in case that particular brand isn't sold in Canada.

Normally, I'm an outdoor gardener. Can you pls explain 'flush the plant when watering'. Does this mean not letting the plant stand in water, letting it thoroughly drain? Thanks for your help, it's greatly appreciated.
\Sandi

I use Dyna-Gro Foliage Pro 9-3-6 plus Pro-Tekt 0-0-3, which gives me a 9-3-9 formula. There's no need to copy those numbers exactly, but I would try to find a fertilizer where the middle number is the smallest. Your 19-31-17 would be more appropriate if the P were, say 6, rather than 31. Adding 5 times more P than a plant can use just raises the TDS (total dissolved solids) unnecessarily. Flushing the plant (which is simply watering thoroughly until water runs out the bottom) removes excess minerals that would otherwise accumulate. And I would never let a plant sit in water.

Here's something I posted about fertilizers:

The uselessness of high phosphorus levels