This year I have planted 8000 seeds in 13" X 11" seedling trays on a 50x50 potting mix and perlite base then covered with 1/4" sand then 1/2" perlite to prevent damp off and fungus knats.
I transplant seedlings as soon as they show signs of forming a true leaf into 2" square pots and so far have about 200 transplanted since mid Aug. the first of which are just starting to bloom. I have had very few losses in the transplants even though I am not really gentle in my method.
The problem is that now(about the last month) I am losing most of my seedlings at the cotyledon stage before transplant. They appear to get a dark “shiny” look on the cotyledon, sometimes on one leaf which will die off. sometimes as small spots which spread until the plant “corrodes” and dies. They do not wilt but are more necrotic and dry looking.
I have used hydrogen peroxide as a treatment (once)and I have used"Seasol" as a stimulant, neither seem to have done any good.
Any ideas on what it is and what I should do about it.
It sounds as though you need to get them out of the tray sooner. Whatever is causing the problem is probably in the tray. I’d suggest that you lift them out as soon as possible after they break the surface, even before the neck straightens out, and get them into whatever you plan to grow them in. It wouldn’t hurt to rinse them off when you lift them out and before you pot them; if there is some sort of nasty organism in the seed flat, rinsing them might get rid of the contamination.
BTW, you’ll discover that there is less transplanting shock and you’ll lose fewer when you move them early, before the true leaves get large enough to be noticeable.
I transplanted all that were up and it is obvious that the stem below ground is also affected as it is discoloured and constricted on the sick plants but the new roots below this area seem strong and healthy.
I dont know what this indicates but it is very surprising.
Russ, I am new here and “hopefully” will start my “journey” into the breeding minefield shortly(this coming weekend hopefully. I have read your post and by my maths your seeds are 3/4" under cover, is this right and if so is that the correect cover for seeds. Why I ask this is I have in my possecion some seeds from America(thanks Kim), me being in Australia, and do not want to stuff them up. Is the potting mix the same all the time or have you changed brands, the same goes for the perlite and sand I guess. I hope some of the brains on here come up with your answer Russ, then there is one less for me to fall in.
I transplanted all that were up and it is obvious that the stem below ground is also affected as it is discoloured and constricted on the sick plants but the new roots below this area seem strong and healthy.
If the stem is tan and firm just below the surface, that’s usually OK. But if the stem is translucent brown, that’s not OK. You can usually save seedlings if you cut above the translucent part until you have firm white stem(use a very sharp knife or a razor) and plant the top section deep, with just the tip of the elbow showing, or if the cotyledons are already open, with the cotyledons spread wide at the surface or together below the surface (it’s OK to gently close them).
Usually the cotyledons have enough strength to let the cut stem end form roots quickly. The seedlings you have to treat this way should be put in a low-light area, maybe at the edge of the lighted zone, until they begin growth. It would be really tiresome to treat a lot of these, but the percentage of successes with this technique is usually pretty good.
It’s a remote possibility, but we once got a bad batch of germination mix. The company had accidentally put in way too much nitrogen. We had heavy losses of various annual seedlings.
White, burnt edges on the leaves can be symptomatic of nitrogen toxicity.
It might pay to try leaching out your seedling flats with some good water. Basically rinsing out the soil.
What I meant was that when I removed the sick seedlings from the soil it was obvious that the stems were “infected” below the surface, but in many cases there was a strong root system growing below the withered and translucent coloured part of the stem.
Jadae.
I am using a 50/50 mix of a commercial “organic” potting mix and perlite about 2" deep, seed broardcast on surface and packed into the surface, then I spread sand on top, just enough to guarantee good contact, then a cover of perlite as protection from insects and damping.
Joe.
I did try leaching. But my observation of the root systems would not indicate fertilizer burn.
I still dont know what the problem is but I will try moving them ASAP in the hope that will help.
That’s what they used to suggest using Captan for. I did it for several years until I couldn’t find it on the store shelves, then discovered it didn’t make a difference. Growing them outdoors, it’s not an issue here. Kim