When tomato plants turn yellow from the bottom up …
Beth in Silver Spring writes: “I’ve been struggling with tomato plant disease ever since we put in our little garden six years ago. I don’t know if it’s early blight or some sort of wilt, but it always starts the same way: Bottom leaves quickly turn yellow, wilt and dry up. I mulch the soil with LeafGro and water only at the base of the plants, but to no avail. I realize that this has been a very rainy season, but it happens every year, so it feels like it’s a soil-borne problem.”
…There’s a sinister spoiler skulking in the soil!
You are correct, Beth. It’s perhaps the most common problem affecting home-grown tomatoes — nasty wilts such as verticillium and fusarium that build up in the soil when tomatoes are grown in the same spot every year.
So move those love apples around . . .
Of course, the best answer is to simply rotate your tomatoes to different locations every season. I know that some sources say to rotate all your crops — and moving everything around is certainly ideal. But with tomatoes, it’s absolutely essential to plant in a different spot every few seasons. These diseases generally show up by the third year of repeated planting, then get worse every season tomatoes are planted in the same piece of ground until it reaches such a crescendo that the plants are often dead by the Fourth of July.
What if you just can’t move them around?
Beth says that she can’t plant anywhere other than her little fenced-in area of raised beds because of the hungry deer in her neighborhood. She asks: “Could I buy a large planter and fill it with clean soil but still keep it inside the fenced-in garden area — on top of the diseased soil?”
The answer is yes, Beth. These wilts live in the soil, not on the surface; many people in your situation do turn to containers as the answer. But you need big containers; you need to only plant one tomato plant per container; you need fresh ‘soil’ (ideally a combination of a soil-free mix that contains lots of perlite and compost—definitely not garden soil), and you’d have to change out the soil mix in your containers after two years of use (but you can use that soil on other plants, just not tomatoes).
In situations where the disease is just beginning to show up, planting resistant varieties — they’ll be labeled with the letters V and F after their variety name — can offer some help, often gaining you another season or two.
So can grafted tomatoes, where the variety you want to eat is spliced onto the root system of a different tomato that’s super-resistant to these soil-born ills. As more people grow some of their own food and garden areas keep getting progressively smaller, grafted tomatoes are becoming increasingly popular. Once only available via mail order, many independent garden centers now stock them in the spring.
Deer-proof tomato cages
Beth feels that her planting options are limited to her small fenced-in area because of rampant deer problems in her neighborhood. She wonders whether she can grow her tomatoes in containers inside the fencing.
The answer is yes, but an easier solution would be to construct the kind of tomato cages I recommend every spring: six-foot long (linear) lengths of welded wire animal fencing formed into tubes that are about two feet across, placed over the young tomato and then supported by driving a heavy stake through the sides of the cage.
Deer can’t reach the tomatoes inside the cages; the cages provide excellent support for the big, floppy plants, and you can easily move the cages to a different spot every year. That would free up the fenced-in area to grow crops that aren’t as fussy about being rotated — which is just about all of them!
Tomato trouble-shooting
It’s the time of year when a host of tomato troubles begin to appear, and here are some solutions to other problems:
- Tomatoes that turn black at the bottom just as they start to ripen have blossom end rot — a deficiency of calcium that can be corrected with sprays of liquid calcium, available at most garden centers.
- And to avoid other disease issues:
- Make sure your tomatoes have strong support — don’t let them sprawl!
- Provide plenty of room for airflow between plants; you’ll get much better fruit from two plants that have a foot of space around each of them than from four plants all crammed together, especially in a wet season like this one.
- Don’t touch the leaves when they’re wet.
- Mulch with an inch or two of compost — not composted manure or any kind of wood mulch.
- And we certainly haven’t had to water lately, but if things do turn dry, water disease-prone plants such as tomatoes and roses only at the base of the plants. Don’t wet the leaves.
- Don’t use chemical fertilizers; in addition to making the fruits taste watery, chemical fertilizers make plants more attractive to pests and disease. You’ll find plenty of organic tomato foods at local independent garden centers. Bonus: all of the natural tomato foods contain the calcium that will prevent blossom end rot!
