Under-watering to the degree it affects the nutrient stream would be accompanied by wilting. If you're not getting wilting, it's almost a sure bet your plants aren't drought stressed.

It's more likely a nutritional deficiency (N, probably) - we can chase that down if you want to, or possibly a symptom of over-watering/compaction/heavy soil.

Al

Hi Al! I'm thinking I should have used your planting mix--and I will, if I can ever figure out where to get the ingredients.

I've seen a slight bit of wilting, but I haven't let them get to the point where it's very evident.

These beans are planted in Miracle-Gro Potting Mix. Does that change the diagnosis?

It doesn't change anything other than add to the possibility that over-watering might be the issue. Lack of O2 in the root zone can have a considerable impact on root function, and therefore nutrient uptake. If you're pretty confident you're not over-watering, I'd guess it to be a need for fertilizer. If you like, sharing what you're doing about nutrition might help narrow things down to where you can be pretty sure.

Al

Actually, I've done nothing about nutrition. From my reading, I got the impression that beans require little to nothing in the way of fertilizer. In fact, I was concerned that the potting mix I used might give them too much nitrogen. Here are the mix's fertilizer numbers: 0.21 - 0.14 - 0.07. The package claims the mix fertilizes for six months.

I'm open to suggestions!

Thanks,
Susan

Great! I have the 24-8-16, and will mix up some half-strength. Many thanks.

Make sure you let us know what happened!! ;o)

Al

It's all good, Al! No more new yellow leaves, and lots and lots of tiny beans.

How often do you suggest I repeat the above feeding?

Also, I was checking out the fertilizers I have on hand, and found a bottle of liquid Starter Plus, by Schultz. It's a transplanting solution, containing Vitamin B1. It's also a 5-10-5 fertilizer, plus 0.1% iron. Would this safer to use than the higher-nitrogen Miracle-Gro I used above? Either of them could be mixed at half strength.

Thanks!

Used at low rates, the 5-10-5 probably won't hurt anything, but it supplies about 12x more P than your plant needs in relation to it's N needs. Since N is the must used element, other nutrients are usually measured as a function of N. While going about the chore of growing, plants use about 6X more N than P, so I can't think of any container culture application where it would be better to use a fertilizer that supplies more P than N. That said, it's not going to kill your plants or cause great harm; it's just that there are better options.

If you were referring to the 24-8-16 as a high N fertilizer ..... it really isn't. Remember, the % numbers mean nothing individually. If there was a fertilizer that was 48-16-32, it's not considered a high N fertilizer any more than 9-3-6. Yes, it has more N by weight than the 9-3-6, but both are 3:1:2 ratio fertilizers and contain the same amount of N. How this works: The instructions for mixing will direct you to use only about 1/5 the amount of the more concentrated 48-16-32 as the 9-3-6; so in the end, you're supplying the same strength solution, even though 1 fertilizer id many times 'stronger' than the other.

The 3:1:2 ratio fertilizers work so well; because there is little excess in the soil. Let's think about what happens when you use your 5-10-5, with 12x more P than necessary. Let's say your plants are looking a little yellow & need fertilizer. You fertilize & all starts to look well, but soon, your plants are running out of N and yellowing again. Since there is still lots of P left in the soil, you fertilize. This supplies a little N (in relation to P) but it alsu supplies another BIG dose of excess P. Now you have LOTS more P in the soil than necessary. P raises pH AND competes with Fe (iron) and other micro-nutrients, the symptoms of which includes the yellowing that comes with deficiencies. As you add more fertilizer in the hope that the yellowing will be reversed, it gets worse instead. When you use a 3:1:2 ratio, the plant uses the nutrients evenly, so they are all becoming deficient at the same time. When you fertilize, you're not increasing a notable excess on ANY element, which is not the case as when using high-P formulations.

If you have a plant that needs to have its vegetative growth slowed, simply switch to a 1:1:1 fertilizer or alternate its use the same 3:1:2 ratio you're using. You can also use 3:1:2 ratio fertilizers at low doses (to restrict N) and supplement the K (many use Pro-TeKt 0-0-3 for this).

A summary: I use 3:1:2 ratio soluble fertilizers on EVERYTHING, unless I am intentionally trying to stress the plant by limiting an element (usually N), and I never intentionally apply a fertilizer that will supply an excess of one or more elements in relation to the other essential elements. Excesses are as bad as or sometimes worse than deficiencies. (Dr C Whitcomb et al)

Al

Glad to see they are doing better. :)

JoJo

Forgot to say you can watch the older foliage & when it starts to look "not quite as dark green as they were a few days ago" you can apply fertilizer - prolly about every 2 weeks - depending on your dosage. If you think the plants are pushing too much foliage and not making enough beans, switch to 20-20-20 or another soluble 1:1:1 fertilizer.

Al

Thanks, JoJo.

Boy, Al, I hope you make your living in education, because you're a natural-born teacher. Thanks for all the info in this thread and elsewhere on the forum. A lot of us would be struggling without you!

I started bush beans and noticed that 1 plant out of the 10 is totally yellow. The plants just have their second set of leaves at this time. Is this a genetic mutation? Will my beans be yellow too?

hello, I appreciate this thread is 9 years old but I have a similar question! My bush bean plants (babies - 1 month old) have been shooting up and recently mini flowers / pods have appeared, but the bottom leaves are turning yellow with brownish spots. Fairly sure I'm not overwatering as I only water when the soil tester says the soil is dry, so I was wondering if it could be some sort of deficiency - a quick Google threw up manganese? They're potted in a 3:1 multipurpose potting soil and perlite. My tomato feed (really the only non-universal plant food I can get my hands on) is 4-5-10 but manganese isn't listed on any of the ingredients, would this help or is it something else these guys are wanting?

Thank you in advance for any advice! :)