Saturday, July 17, 2010

How To Propagate Tomatoes Or How to Save Tomato Plants With Blight

This year I lost two tomato plants to a mysterious disease that turned the lower plant stems black. The blackened section dies and the rest of the plant above the damaged portion dies too because it cannot get water. I went ahead and bought new tomato plants, but one of them that was planted into the same location also began to turn black.
I wasn't sure at the time what was turning my tomato stems black, but I have figured out a way to save the tomato plants from dying. The tomato plant above the damaged section is basically alive and well, so the trick is to give the upper portion an ability to obtain it's own water supply.
You will notice that, just above the damaged section, the stem is very bumpy. The tomato plant actually WANTS to grow roots to get water.

Here's what I did:
  1. Take a sheet of plastic and put some good quality soil in the middle.
  2. Tie the two corners of one side of the sheet together. Do the same with the other side. Now you have a pouch with soil inside.
  3. Take this soil pouch and wrap it around the stem under a leaf joint so that the soil is touching the stem. In the case of blight, this will be the good section above the black part.
  4. Take the loose corners of the two pouch sides and tie them together.
  5. Get help! Have someone hold the soil bandage up.
  6. Support the soil bandage. Use string or long twist ties to support the soil bandage by tying it to the leaf joint. You can also prop a piece of wood or another object under the soil bandage to hold it up. Be careful not to pull your plant over if your plant is unable to hold up the weight of the soil bandage.
Honestly, it looks like crap. It's a giant ball of soil wrapped around a stem of tomato plant.
But look at what happens after a couple weeks. Since the tomato plant wants water so badly, it starts to grow A LOT of roots really fast. They even grow out of the damaged black portions!
Once your soil bandage looks like there are lots of healthy white roots growing into it, you can cut off the stem under your soil ball. Put it down and carefully remove the plastic wrapping by cutting it open. If your plant has black stem, be sure to cut away all the black portions.

Now you can plant your rescued tomato plant into a new location.

What is the black stuff?

I looked this up and it appears to be a fungal infection called Blight or Late Blight. The spores are found in infected soil and they splash up onto the plant stems when you water your plants.
This is probably how the lower parts of the stems got affected on my plants and why I am able to save the upper portions. Infected plants can be purchased from big stores like Home Depot or Walmart, and the disease spreads easily there because the plants are in such close proximity. It's moist there, there's not much air flow, and that means good conditions for fungal infections to spread.

I suspect that some of the early tomato plants that died were infected plants. After they died, the spores sat in the soil, and they splashed up onto the new tomato plant and infected it too.

You're actually supposed to destroy infected plants. You're not even supposed to compost them. However, I don't really want to destroy my tomato plants, and I don't mind a good experiment (as you know). So this will be an interesting test to see if the newly propagated tomato plants will live and produce good fruit.

If you live near farms or areas where your infected plants could affect someone else's crop, you should probably get rid of your plants. Since mine are isolated and in the city, I don't have that issue.

Can I eat tomatoes infested with Blight?

You can eat tomatoes from blight-infected plants. It's okay. However, a really badly infested plant will produce hideous tomatoes with ugly black spots on them. I'm not sure if mine will be okay yet. We'll see.

What causes Blight? How can I avoid it?

Blight spreads easily in cold, wet weather which we had earlier in the season, but it is slowed down by hot, dry weather which we have now.

You can discourage/avoid blight in your garden by giving tomato plants a lot of breathing room. In fact, you can even trim tomato plants that have too many leaves and look overly dense. Just cut off some extra stems/leaves that look weak or don't seem to have a useful purpose. Don't get the foilage wet when you water the soil (so spores don't splash up on the stem and leaves). And ensure that leaves have a chance to fully dry out each day.

You can also avoid it by buying blight-resistant plants.

Blight can also affect potatoes. It was actually responsible for the Irish potato famine of the 1840's. So be careful if you have infected tomatos near potato plants.

Well, I hope that helps you out with your tomato growing. I love eating tomatoes fresh from my garden, and they taste so much better than store-bought ones!

Happy Gardening!
How To Propagate Plants


VTbabe said...

Hi, there--

Stumbled on your very interesting blog post just now on your tomatoes and thought I'd give you a little bit of feedback since somebody's given you some not so good info on the dread Late Blight.

I'm not so sure it's what your plants have, since Late Blight on tomatoes usually affects both leaves and stems, but I don't really know what else to suggest.

I know I've read somewhere about some pest that invades the stem and cuts off the plant's ability to draw water through the roots, which is what it seems was happening with yours, but I'll have to go dig a little more to find it.

In any case, a couple of other points about Late Blight. Most important that it does not live in the soil. Other slightly lejss devastating fungal tomato diseases do, but not Late Blight, which requires living tissue to survive.

So no worry about infecting the soil or getting it from the soil. It actually comes as spores on the wind, which stick and multiply in moist, cool weather. The hot sun apparently kills them.

Last year, there was Late Blight all over the continent, as you know. While it was originally thought that it came north from a big grower in Alabama who supplies big box stores and the like with plants, I believe that's since been debunked, and it's really neither fair nor correct to suggest that these stores regularly carry infected plants.

Still, it's definitely a better and safer practice to buy plants from small local growers, if you can, than from anonymous mega-suppliers to big box stores.

What we did have last year, though, was that awful weather, and at least where I am in mid-Vermont, many days of southerly winds to blow the spores up from the south, where the disease is much more common.

In any case, it's generally quite a rare disease in northern areas because that requirement for living tissue means it gets killed off over the winter.

The one place it can survive is in potatoes, which is why one should never use supermarket or even farmers market or one's own potatoes as seed potatoes, but only certified disease-free from reputable suppliers.

Late Blight is back this year already in some areas up north, and so far has been attributed entirely by ag officials to potato growers who got infected last year and didn't make sure their infected tubers were destroyed or left on the surface to freeze (and kill the spores) over the winter.

As above, there are lots of other nasty fungal diseases that hit tomatoes (I had both Early Blight and Septoria Leaf Spot on mine), and the tactics you outline of leaf and branch trimming and watering at the roots, etc., are all things that help avoid or minimize the effect of those diseases.

I'll be very curious to see how your interesting experiment with your diseased tomatoes works out. I'm pretty sure if they survive and do fine, that means they did not have Late Blight after all.

But I'm with you, a summer without tomatoes from the garden is hardly worth living!

By the way, you might want to check out a terrific site called Tomatoville, which is just loaded with people from all over the world, actually, with various tomato problems and ideas and suggestions. I think they'd be fascinated to see what you've done here, and might be able to help figure out what was wrong with the plants that caused those lesions. said...

Oh wow! Thanks for leaving all that wonderful information, VTbabe! That's really useful to me and to anyone else that might happen to read this post.

It would be really interesting if the disease on my tomato plant ISN'T blight since that means more possible research for me to find out what exactly it is. I will have to check out Tomatoville to see if someone there knows what's going on with my plants.

The good news is that the recent hot weather seems to have put the now-mysterious-again tomato illness in check. Both the propagated portion AND the lower portion are still alive. The blackness is also less black now...

Since I have changed so many factors (I added coffee grounds to the soil, added composted manure, added mushroom manure, it's sunny and hot now) it's hard to tell what might have caused the most improvement in my tomato plant health.

At any rate, thanks again for all the info and for stopping by to read my post!

Have a great day,

VTbabe said...


Boy, I didn't realize you'd kept the "black" portion on the plant. I'd say for sure, if you didn't cut that off and throw it away that it's not late blight or any other fungal disease because the spores would surely have reached the rest of the plant by now.

The hotter weather won't stop it once it's on your plant, although it will slightly slow down the progress. But gee, by now, I think your plants would have been overcome, since LB really moves very, very fast usually.

I know people who reocgnized it on their tomatoes last summer, rushed off to the ag store up in town to try to find a remedy (there is none, alas), and by the time they got back a couple hours later, the plants were all dead!

If I were you, I'd definitely cut that off and dispose of it in the trash because whatever it is, it can and usually will spread to the healthy tissue.

Media reports on Late Blight can be very misleading because too often the writers don't really understand it. I remember there was a very bad and deceptive one even in the sainted NY Times last year.

I've learned with gardening to totally trust only the ag school and state/county extension Web sites for info on pests and diseases and their remedies. They serve primarily commercial growers, so they really have to get it right. Whereas an awful lot of us home gardeners are a little less, um, precise, shall we say.

When Late Blight showed up all over the place last year, and at the same time my tomatoes came down with something(s) awful, I did a lot of reading and researching on the Web, and have continued this year, so I maybe know a bit more about it than the average layman. (I HATE not knowing what's going on in my garden for sure, don't you?)

I did finally get the Late Blight at the very end of the summer, luckily after I'd gotten in my harvest, such as it was, so I've at least seen it once.

This year, knock on wood, my plants all seem healthy and happy. By this time last year, they were already in trouble and I was frantically clipping off more infected leaves and branches every single day in an attempt to slow it all down. UGH!!

Congrats to you, by the way, as I gather you're in the city but still doing what you can to grow your own. I heard recently about a guy living in an apartment in NYCity who was so keen on growing his own veg, he bought a second-hand pick-up truck, filled the bed up with topsoil and planted a bunch of stuff and parked it on the street where it got enough sun. How cool is that?

VTbabe said...

Oops! Sorry about the multiple repeats! Something funk about the blog software kept telling me something was too long, not clear what, and that my comment had been rejected. Not so, apparently.

Hope you can delete the repeats... said...

Hi VTbabe,

Well, I thought I cut off the black portion. It's definitely gone on the original plant. However, my mom told me today that my dad didn't cut it off of the other one (the propagated one) before he planted it into the ground for me. I almost had a heart attack when I heard that, but I looked at the propagated stem and it seems fine.

Considering how well the previously-ill tomato plant is doing, maybe it was a more blight/mysterious disease resistant variety? I have no idea. It's starting to form fruit now, and I keep waiting for them to turn black and fall off :P So far so good.

It's great that you're so well-read on late blight now! A lot of my knowledge is trial and error, hehehe!

That's very cool that the city fellow made his own garden in his truck! My family moved from a townhouse to a house last Fall so I suddenly have a lot more space to work with! It's heavenly, but the work never ends! I can spend hours in the garden and hardly notice it. Sadly, all that time spent hardly makes a dent in the never ending list of things to do in the garden :) Especially when it comes to weeding...

The cool thing is that this garden came with a lot of new plants for me to experiment on, and Home Depot's Garden Center is super close. Woo hoo!