Mid-July Fertlize or Not?

cmcramer · 2024-07-07T15:24:46+00:00

Starting with average garden soil (sorry, no soil test!) which has grown good quality flowers/veggies in previous seasons, I added one TEASPOON of Osmocote...

SteveM

JessieC The few feeder roots on the tuber in your photo have me wondering about something I should probably know: I understand young plants will get their nourishment from tubers until they develop feeder roots. But how many feeder roots does it take before a plant is getting enough nourishment from the soil to make a difference. Is it possible your plants are still too young to be getting nourishment from the soil and, instead, are still being fed mainly from the tuber? If this were the case then no amount of fertilizer would make a difference. Right?

JessieC

SteveM That is an excellent point. Also, I pulled that tuber out of the ground to inspect it more closely, and ended up removing a lot of the feeder roots by mistake. These have been in the ground for about ten weeks, so they are definitely stunted. I do plant in pairs generally, so it's easy enough to try the experiment with the fertilizer (I found a small package of the exact one you mentioned for $6 today!) This one is Small World, and I have pairs of Glenplace and Odyssey that look equally bad, or even worse. I wonder if it's spider mites after all. It's just strange that it is limited to this bed.
I think I will go out and hover some more. I am told that helps a lot!
Thanks

SteveM

JessieC I have also had Broad mites and Cyclamen mites on dahlias at various times. Both are small so a 15X (or greater)hand lens is needed to see them. Broad mites prefer the new growth and can make a plant look similar to a DMV infestation. One year all of my Cafe Au Laits were badly infested with Broad mites . They were very stunted and the leaves were deformed. This gave me a good excuse to cut them all down.

JessieC

SteveM Well I hate to say it, but it looks a lot like mites to me. (Apologies for these gruesome photos 🤢)
This is a closeup of Odyssey, which is the one that looked like spider mites before. I chopped one plant down and trimmed the other a few weeks ago. Glenplace also looked afflicted, and I trimmed that pair as well. Oddly, Glenplace in another part of the garden also looks like this. But they were never together. The third one was a cutting. Odyssey is in another part of the garden and looks fine, albeit not my greatest plant. The other plants in this bed are all suffering, and I bet it’s a combination of things.
Given that the weather is going to be mild this weekend, I’m thinking that I’ll give them all a serious trim (à la @tobi from Georgia.) I’ll remove the netting so I can get in there and inspect some roots too. Maybe I’ll even dig up and replant a few to try your Miracle Grow experiment. On the other hand, a proper soil test is $15 and could answer lots of questions! Or none at all.*
My understanding is that combating mites with miticide is a tedious and expensive process. As much as I like the term “miticide,” I have to conserve energy for the groundhog who’s decimated my bed of zinnias. Thankfully, I don’t see these kinds of symptoms elsewhere in the garden.
As always, I remain open to (and grateful for) advice from my fellow dahlia nuts. It’s good to be amongst like-minded enthusiasts!
*ETA I suppose a soil test might suggest that a particular deficiency left these plants vulnerable to a mite infestation. 🧐

SteveM

JessieC Well I hate to say it, but it looks a lot like mites to me

My eyes aren't reliable enough to say for sure but it sure does "feel" like a spider mite infestation. You should see red dust-size particles that move (adult mites) and probably webbing? I don't see leaf distortion so I doubt it is broad mites. The first sign of spider mites is interveinal stippling on the surface of leaves (as in your photos) which is caused by mites feeding under the leaves. Spider mites multiply amazing fast so, no matter what you use to control them (miticides, beneficials, or spraying water), it should be started as early as possible. For your situation, (assuming you positively see mites) I would remove(and bag) as much of the infested foliage as possible and continue misting/spraying the plants with water. Try to spray under the leaves if possible. You might consider introducing .beneficials. I wouldn't recommend miticides because once you start spraying miticides you have to spray regularly and rotate with different miticides. This can get expensive so best left to commercial growers or show enthusiasts. You should also be aware of transferring mites on your clothing from the infested bed to the others.

JessieC *ETA I suppose a soil test might suggest that a particular deficiency left these plants vulnerable to a mite infestation.

I think you nailed it. Weakened/sick plants invite pests, healthy plants ate attacked last. After some Googling, it seems there is no easy way to remove excess phosphorus from soil. It seems the best recommendationis to grow certain cover crops and pull the cover plants up when mature. A soil test on this specific bed might be worth the investment for guidance going forward. If you collect samples avoid soil that you have recently fertilized.🙂

JessieC

SteveM It seems the best recommendation is to grow certain cover crops and pull the cover plants up when mature

Ah. Well given the way these plants look now, I see a cover crop in my near future! 😬
And I did put some leaves under a 10x magnifying glass. Honestly, I don't see anything moving on them. But I've been bagging and tossing the foliage, and treating what remains to a thorough spray of water. Who knows? Maybe they'll bounce back before the frost, which is likely November.
I had labeled this bed the "pom and miniball community" because I was hoping to get seeds off of Odyssey. Alas, seeds may be a little too advanced for me at this stage.I'm glad you mentioned the issue of contamination. I've been treating it like an outbreak for sure! For now, I will focus on keeping the rest of my plants happy. The other 70-odd dahlias are doing alright, and I am glad this problem appears to be localized.
Thanks so much for your help!!

Teddahlia

Removing phosphorus is fairly easy for a farmer who harvests a crop. My strategy has been to remove the dahlia stalks every year. It works but takes several years to achieve visible results. My "poison row" where I used "more bloom" products to grow "better" flowers is still showing negative effects after about 5 years. The biggest fertilizer myth of all is that dahlias need little nitrogen and lots of phosphorus and potassium. Professional farmers use soil tests to determine fertilizer needs. Adding fertilizer because some "so called" expert says that is what dahlias need is some of the worst advice concerning dahlias out there.

JessieC

Teddahlia Agreed! I am so glad I knew this (from this group,) and that I did not compound the problem with more fertilizer. The soil I bought came with all that extra Phosphorus already in it. My soil tests have paid for themselves many times over. Both the P and the K came down last year in the large bed that I tested again. I'll gather soil from this bed soon and I will report back!

SteveM

Teddahlia The flower grower who grew in my field, before I leased it, heard that Phosphate was good for flowers. So, he liberally fertilized with Triple Super Phosphate (0-45-0). I compounded the problem by adding lots of Milorganite (6-4-0). I got the lease cheap because the old farmer said nothing would grow in that soil He was mostly correct.

mocullen35

Alternatively, maybe baby thrips? I had a bad baby thrips issue last year in one bed (as diagnosed by my local nursery after looking at a few leaves under a microscope). They sucked the leaves of everything and they were silvery/shinyish and and covered in grey/black dots, the teeny thriplets were off white and longer than a mite. I stripped the leaves and used captain jacks a few times. They grew back and looked great. I've been overhead watering at night to hopefully avoid the issue this year
.

JessieC

mocullen35 That’s interesting. And a good reminder that thrips are a thing. I have been unable to treat with Capn Jacks due to the heat, but can start adding that to the schedule. So far, I’ve just seen some June bugs and the odd beetle.
Thanks for the insight!

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