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Calgary Alberta Canada

So I've been using 15-30-15 for the pumpkins roots. I'm wondering when I should switch to a high potassium ratio for vine growth? How do I know when the plant is ready?

6/14/2015 12:27:22 AM

Anamosa, IA BPIowegian@aol.com

Nitrogen, the first number is for vine growth. Potassium, the third number is for fruit growth. What you have been using should be giving you decent nitrogen. As you get close to pollination, you want to stop the nitrogen. If you send the plant into a big burst of green growth, your pumpkins will abort. I had that happen a few years ago with one plant. It set tons of pumpkins that all aborted at 4" to 6" diameter. Unless you got a late start, I would hold off on fertilizer until you have a pumpkin that is at least beach ball size. You have to be careful with potassium. Too much will make your pumpkin mature too quickly and shut down growth. And if you are using Pumpkin Pro or another micorrhizae inoculant, you don't want too much phosphorus. Excessive phosphorus suppresses micorrhizae.

Unless you have very well to excessively drained soil that allows salts to leach out, you don't want to use soluble fertilizers too much. They are high salt content and long term use can be bad. That is why I try to get my nutrients into the soil before planting, using mostly organic sources. My soil is silt over sand, and I don't have a salt problem. But I limit my soluble fertilizer to 3 very light drench applications to get the plants going in a cool spring like this year, and 3 or 4 light foliar applications in September to keep the growth going. I use either Schultz or Miracle Gro tomato fertilizer, as they are fairly balanced and have some of the micro nutrients too.

6/14/2015 9:41:57 AM