Problem with my hop plants: yellowing of new growth. Advice?

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Corbeermite

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Hi all,

I'm container growing some hops in large, 20 gallon planters, and have run into a bit of a snag. I'm growing two different varieties: Willamette, and Sterling. This is their first year, started in mid-April from rhizomes. The planters were filled with a mix of about 50% potting soil, and 50% compost, mainly composted yard waste and spent grains.

While growth has been good, for the past few weeks, new growth has been pale green in color, and delicate/translucent, with a bit of leaf curl at the margins. Some, but not all, of the newer leaves that form develop yellow spots that seem to eventually become holes or deformations in the leaves. Older leaves are a dark, healthy green, and show no signs of yellowing or curling. There has also been some wilting, but curiously only at night. Both plants perk up nicely during the day. Both plants are showing the same symptoms, but the Sterling is showing symptoms more strongly than the Willamette.

Thinking this might be a case of nutrient deficiency, I applied a mild solution of Miracle Gro, the older 15-30-15 formula, at 1/3 of normal strength. Things seemed to improve for a few days, then worsened slightly. A week later, two days ago, I applied another dose of Miracle Gro at 1/2 of normal strength.

This time, something strange happened: today, 48 hours later, new growth is showing a pronounced yellowing, starting at the center of the leaf, and radiating outwards towards the margins. The same thing is happening on both plants. Many of the topmost leaves are doing the same thing. The older leaves, toward the bottom, remain healthy and dark green, with no signs of yellowing or curling.

I can't quite figure out what's wrong, despite some furious googling and forum reading. The outward radiating yellowing reminds me of iron or sulfur deficiency, but Miracle Gro has both sulfur and iron. The best I can come up with is manganese deficiency caused by a soil pH that's too high, maybe due to our fairly alkaline tap water, but I'm unsure if a manganese deficiency can suddenly intensify so severely. I don't have a way to measure pH beyond some broad range test strips, but the runoff I tested came out approximately neutral. I'm not sure if that casts doubt on high soil pH or not.

Any advice would be greatly appreciated. I'm happy to answer any questions, or provide any information I may have missed.

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Soil pH optimal for most plants tends to be slightly acidic, in the range of 5.8 - 6.2. Hops can thrive in a large range, but will require supplementation outside of that. You mention micronutrient deficiency, and that's a likely cause (as an initial guess). Just because something has iron and sulfur doesn't mean the plant will be able to uptake the nutrients. As well, you mention you have hard water, so every time you add water, you're increasing the alkalinity or salt concentration, but also increasing soil pH as a result.

I recommend trying distilled water to help leach out any salts over the next several waterings.
 
I'd stop using Miracle Gro and switch to a slow release fertilizer to see if Miracle Gro may be the source of the problem. Years ago when I used it for general gardening, I often got the same thing you're running into. I use a mixture of blood and bone meal with great results for both my hops and garden.
 
Soil pH optimal for most plants tends to be slightly acidic, in the range of 5.8 - 6.2. Hops can thrive in a large range, but will require supplementation outside of that. You mention micronutrient deficiency, and that's a likely cause (as an initial guess). Just because something has iron and sulfur doesn't mean the plant will be able to uptake the nutrients. As well, you mention you have hard water, so every time you add water, you're increasing the alkalinity or salt concentration, but also increasing soil pH as a result.

I recommend trying distilled water to help leach out any salts over the next several waterings.

Great information, thanks. That's my suspicion as well: with fresh soil and compost, it's not that the nutrients aren't there, it's that there's no uptake for some reason, probably pH related.

I have an RO filter for my brewing system, so I'll make some RO water for the next watering and see if that improves the situation.

I'd stop using Miracle Gro and switch to a slow release fertilizer to see if Miracle Gro may be the source of the problem. Years ago when I used it for general gardening, I often got the same thing you're running into. I use a mixture of blood and bone meal with great results for both my hops and garden.

Yeah, it seems to do a good job on vegetables, but I've never had much luck using it on anything else. I'll probably stop fertilizing for a bit, since they shouldn't have needed it yet anyway. Later in the season, providing they recover, I can look at some better options. Thanks!
 
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