📌 Quick Summary (TL;DR): Early Planting & Disease Risks
- 🥶 The Cold Soil Trap: Growers share real-life experiments of transplanting tomatoes into unheated greenhouses too early (mid-April in Zone 4). The result? Stunted growth, delayed fruit set, and tomatoes ripening weeks later than plants set out in warmer soil.
- 🌱 The Seedling Stress Connection: A fascinating insight from a plant pathology expert is discussed: Leaf Mold (Cladosporium) often infects plants very early, around the 7th true leaf stage. Why? Because this coincides with “hardening off” and early transplanting. Packing seedlings tightly under plastic covers in a cold, damp greenhouse creates the perfect incubator for spores.
- 🛡️ Prevention: To combat this latent infection (which has a 70-day incubation period), growers highly recommend applying preventative fungicide sprays (like Copper or modern systemic options) immediately after transplanting into the greenhouse.
- 🔥 Soil Warming Tricks: To avoid transplant shock, growers suggest planting through clear/black plastic mulch or using black plastic grow bags to pre-warm the soil before early planting.
📝 Editor’s Note: Cultural Practices & Fungicides
- Trench Planting (“Laying them down”): You’ll see a grower mention planting tomatoes horizontally (trenching). This is a common practice for leggy seedlings, allowing the buried stem to grow a massive secondary root system. However, doing this in cold spring soil can severely stunt the plant, as deep soil is colder than surface soil.
- Akhatov: Mentioned in the thread, Askar Akhatov is a highly respected Russian agronomist and author of definitive textbooks on greenhouse plant diseases.
- HOM / Strobi: “HOM” is a common brand of Copper Oxychloride (a standard copper fungicide). “Strobi” contains Kresoxim-methyl, a commercial fungicide available globally.
Lyudmila, you transplanted your tomatoes early this year. Could you share your impressions—did you like early transplanting, is it worth it, and will you continue to practice it? And another thing: do you think Leaf Mold (Cladosporium) could have run rampant precisely *because* of the early transplanting? Maybe the plants were weaker than usual due to the cold stress?
Marina111 wrote:
Lyudmila, you transplanted your tomatoes early this year… do you think Leaf Mold could have run rampant precisely because of the early transplanting?
Marina, how are you? Are you back from the dacha?
What have you decided about your own plantings? I think it’s impossible to sow all tomato seeds at the exact same time.
I can’t change my habits; I will continue to sow in different batches, at different times. What if spring comes early and it’s warm at the end of April?
Besides, sometimes things don’t germinate. Lyuda praised the determinate variety Rozoviy Gay (Pink Grove), so I ordered it, and I also ordered the determinate hybrid Pink Bush F1. So right now I’m rustling through my seed packets, sorting them out.
gala7496 wrote:
Marina, how are you? Are you back?… I can’t change my habits; I will continue to sow in different batches…
Galya, thanks! Everything is fine with me, just a lot of errands in the city and fatigue has piled up.
I wasn’t referring to early *sowing* (indoors), but specifically early *transplanting* into the greenhouses. I’m interested in how the plants tolerate living in the cold and whether such a start affects their further development, particularly their susceptibility to diseases.
Good evening, Marina and everyone else. May I answer your question about early transplanting based on my experience specifically this year? Then Lyudmila can write her thoughts; maybe this will be useful.
I sowed my tomato seeds on February 17th. I transplanted one greenhouse bed on April 16th, and the other bed on April 24th. The ones on April 16th I planted horizontally (trench planting) to a depth of 7-8 cm (3 inches), and the ones on April 24th I planted normally.
The result was this: the tomatoes took a VERY long time to get going, set fruit late, and the first red tomatoes only appeared in mid-July! My tomatoes have never started ripening that late; late June to early July was always when I got my first ripe tomatoes. I assume that the unheated soil was to blame. So, it’s my fault for planting them in cold soil. Even though I measured the temperature and it seemed okay, the days were warm but the nights were cold, and the deep earth hadn’t warmed up yet. That is my experience from this year.
Hello everyone! I sowed and transplanted on those exact same days, but the soil temperature in my greenhouse in mid-April was 2 degrees (Celsius) higher than in other years. For the second year in a row, my tomatoes suffer from the intense sun—I have to use shade cloth.
They ripened on time—we’ve been eating them since June—but there were a lot of skipped blossoms on the trusses, missing trusses entirely, and the overall yield was smaller. Granted, I used to plant two greenhouses full, and now I only plant one, and not packed to the brim. I had almost no Leaf Mold last year, and it didn’t run rampant this year either—I spray with iodine and milk.
Marina111 wrote:
Lyudmila, you transplanted your tomatoes early this year… do you think Leaf Mold could have run rampant precisely because of the early transplanting?
Marina, every year I try to transplant as early as possible. Moreover, I bring the seedlings out into the greenhouse in early April. First I bring them back into the house at night, but starting from the second ten days of April, I leave them there overnight without supplemental heating.
I think this does affect fruit set, seedling development, and early diseases. I can’t say it happens like this every single year, but definitely the last two years.
However, with the early transplanting of the determinate Pink Bush (around April 17th) into a sunny, warm spot without supplemental night heating, the results were simply excellent. No diseases, no skipped blossoms right up until autumn.
For planting next year, I will be even more meticulous in selecting varieties. And I will sow and transplant everything (except early determinates) much later.
Rosinka wrote:
The result was this: the tomatoes took a VERY long time to get going, set fruit late…
Natasha, many people’s tomatoes behaved like that this year, including mine, even though I didn’t transplant them until early May.
Nessi wrote:
They ripened on time—we’ve been eating them since June…
Interesting, why did they set fruit late near Kaluga, but right on time in the Moscow region? Maybe the spring in Kaluga was colder?
Aleksan9ra wrote:
…early transplanting of the determinate Pink Bush… results were simply excellent. No diseases, no skipped blossoms…
Lyuda, well that one is probably an F1 hybrid, right?
Maybe when transplanting early, we should plant through plastic mulch? Cover the ground early to warm it up, leave the plastic on during planting, and only remove it when it gets completely warm. That way the soil won’t cool down so fast.
Marina111 wrote:
I’m interested in how the plants tolerate living in the cold and whether such a start affects their further development, particularly their susceptibility to diseases.
I planted tomatoes outdoors in early June. And only slightly earlier in the greenhouse. Well, I didn’t even arrive at the dacha until May 26th. So everything was already warm. The outdoor tomatoes got Leaf Mold. In the greenhouse, there was almost none at all. But my greenhouse has brand new polycarbonate, and nobody knows when the old one was blown off by the wind.
Galiy wrote:
The outdoor tomatoes got Leaf Mold. In the greenhouse, there was almost none at all.
So it turns out that outside it was colder for them and Leaf Mold popped up, while in the greenhouse they didn’t freeze and were fine? On the other hand, early June really isn’t that cold. Did you use row covers outdoors?
Good evening everyone. Soil warming also depends on the structure of the soil itself; if it’s more sandy, it warms up faster. It also depends on the amount of sun. My greenhouse is in the shade in the morning until about 9:00 or 9:30 AM; across the road, the neighbors have huge trees blocking the east.
But the spring was also cold this year; our April was cold. I used to transplant at these exact same dates, and the whole development process went differently, which is why I got my hopes up. I also always bring them out to the greenhouse in the first ten days of April, but I put them under low tunnels/hoops, cover them with spunbond frost blanket, and if the nights are freezing, I throw plastic film on top of that.
I transplanted outdoors on May 11th under a row cover, but I don’t keep them under it for long. As soon as it gets somewhat warm, I open them up, but I do have a canopy over them. I didn’t have any Leaf Mold this year either in the greenhouse or outdoors. I sprayed with Luna Experience. Prior to 2021, Leaf Mold tormented me inside and even occasionally outside.
Marina111 wrote:
So it turns out that outside it was colder for them and Leaf Mold popped up, while in the greenhouse they didn’t freeze and were fine?
The summer was hot. I planted in mid-JUNE. It was hotter in the greenhouse. It only started getting colder towards mid-September. I think the reason is something else.
Good morning everyone and have a great day! It’s warm and sunny here!
Regarding Leaf Mold (Cladosporium), I read in a book by plant pathologist Askar Akhatov that, under certain conditions, it can appear while they are still seedlings. The most favorable moment for infection is when the 7th true leaf appears. Why specifically then?
Maybe it’s because this is exactly the time when we start subjecting our seedlings to various forms of “hardening off.” Sometimes you place the seedlings in the greenhouse, the trays are packed close together, the seedlings are dense, there is no ventilation, and they are covered on top to keep them warm. Then, as luck would have it, a cold snap hits with a series of cloudy days—and bam, you’ve created the perfect conditions.
After the initial infection, it takes approximately 70 days (if I’m not mistaken) before the disease begins its intense, visible development. Again, everything depends on the conditions.
This is why professionals recommend treating seedlings at least twice for prevention immediately after transplanting.
Marina111 wrote:
Lyuda, well that one is probably an F1 hybrid, right? Maybe when transplanting early, we should plant through plastic mulch?
Marina, yes, it’s a hybrid. But not all hybrids are resistant to Leaf Mold. For example, my Sarra F1 was the first one to get infected.
Yes, you can use plastic mulch. Also, this spring, the method of warming the soil in black plastic grow bags worked very well. For early seedlings, you can start doing this earlier.
Aleksan9ra wrote:
This is why professionals recommend treating seedlings at least twice for prevention immediately after transplanting.
Good afternoon everyone! Lyudmila, what is the best thing to treat them with for prevention?
Lyudmila, there are many fungicides available now, but in this case, you can use the simplest copper-based ones, for example, HOM (Copper Oxychloride / Copper Fungicide).
Lyudasik wrote:
Lyudmila, what is the best thing to treat them with for prevention?
You can do one round with Luna Experience, and the second round with a different product like Strobi.
Svetikk wrote:
You can do one round with Luna Experience, and the second round with a different product like Strobi.
Sveta, I paid attention to Strobi; you mentioned it in another thread. But Strobi wasn’t available in our group buys this year, and it probably won’t be available next year either.
gala7496 wrote:
But Strobi wasn’t available in our group buys this year…
I have a stockpile of Strobi and Strobitec. By alternating it with Luna and something else (I forget what, my notes are at the dacha), I had absolutely zero Leaf Mold in my greenhouses this year.
Svetikk wrote:
I had absolutely zero Leaf Mold in my greenhouses this year.
Yes, I remembered that; I think it was in the regional chat thread. Unfortunately, I only had Luna, but maybe that helped too.
Aleksan9ra wrote:
The most favorable moment for infection is when the 7th true leaf appears…
Lyuda, my extra backup seedlings went outside and grew right next door. The ones in the greenhouse didn’t get Leaf Mold. The one that suffered the most from Leaf Mold was the hybrid Fenomena F1, but that whole batch went outside; the ones in the poly tunnel didn’t get it. And the Tulip and Grapefruit varieties growing right in front of it were perfectly fine.
Later on, I grew to love planting them into warm soil with plenty of space. Yes, the harvests are later, but the tomatoes don’t suffer transplant shock at all. The summer was definitely good this year; maybe another time there won’t be a harvest, just like with late-planted onions.
Girls, they sell Strobi in small consumer packets in our local stores.
