Oregano? I hardly knew her!
June 4, 2006 8:57 AM Subscribe
Gardeners, a call to arms! Something is killing my oregano!
I have two different cultivars of oregano in pots (mountain greek and zorba rose). They had been growing rather well, and the mountain greek still seems to be, however...
The zorba rose is having several of its leaves blacken and die, from the ouside in. First the tip of the leaf will blacken, then eventually the whole leaf.
Additionally, new growth on both plants is strangely yellow. New baby leaves will be yellow to yellow-green, with darker green veining.
I don't think I'm under or over-watering...I check regularly by digging a finger into the soil and feeling for moisture. Still, could it be a watering issue? Could it be fungal?
I live in North Texas, and the plants have Northern exposure. They get morning and some evening sun, and are shielded from the hot Texas afternoon sun. I would say they get watered about every 3 days or so.
Additionally, my rosemary is doing ok... but not really taking off. Tips on that one would be appreciated, too.
I have two different cultivars of oregano in pots (mountain greek and zorba rose). They had been growing rather well, and the mountain greek still seems to be, however...
The zorba rose is having several of its leaves blacken and die, from the ouside in. First the tip of the leaf will blacken, then eventually the whole leaf.
Additionally, new growth on both plants is strangely yellow. New baby leaves will be yellow to yellow-green, with darker green veining.
I don't think I'm under or over-watering...I check regularly by digging a finger into the soil and feeling for moisture. Still, could it be a watering issue? Could it be fungal?
I live in North Texas, and the plants have Northern exposure. They get morning and some evening sun, and are shielded from the hot Texas afternoon sun. I would say they get watered about every 3 days or so.
Additionally, my rosemary is doing ok... but not really taking off. Tips on that one would be appreciated, too.
Best answer: Could you take a photo? Do you leave the plants outside at night, with wet leaves? It could be a fungus of some sort...the spores of lots of plant funguses travel on the night air and attach themselves to moist leaves.
It could be some kind of mineral deficiency (upon preview, as ewagoner says). Do you have them in potting soil, or plain dirt from your yard? You may have to cut in some fertilizer or additive if the plant isn't getting enough nutrients from its growing medium.
There are so many options here. It also sounds like maybe one or two other things - either black rot, or some kind of root disturbance.
If it's black rot, you have to cut off all the affected limbs, and sometimes, if it's bad enough, you have to just get rid of the plant and its soil altogether. You'd throw them in the trash, not burn them or add them to your compost.
The root disturbance seems unlikely, because it sounds like your plants are pretty well established, but I'll mention it anyway. If there are any air pockets in the soil, or the plant was disturbed recently, not enough water would be getting to the edges of the leaves. The leaves would then dry and turn black. If you're unconsciously overwatering (you say that you aren't) to make up for the drying leaves, the new growth would be yellow from too much hydration. Are the blackening leaves dry, or mushy, or just the same texture as the green leaves? Over or underwatering can also cause root death, and in either case, root death can manifest itself in older leaves turning black, and new growth being yellowish.
posted by iconomy at 9:31 AM on June 4, 2006
It could be some kind of mineral deficiency (upon preview, as ewagoner says). Do you have them in potting soil, or plain dirt from your yard? You may have to cut in some fertilizer or additive if the plant isn't getting enough nutrients from its growing medium.
There are so many options here. It also sounds like maybe one or two other things - either black rot, or some kind of root disturbance.
If it's black rot, you have to cut off all the affected limbs, and sometimes, if it's bad enough, you have to just get rid of the plant and its soil altogether. You'd throw them in the trash, not burn them or add them to your compost.
The root disturbance seems unlikely, because it sounds like your plants are pretty well established, but I'll mention it anyway. If there are any air pockets in the soil, or the plant was disturbed recently, not enough water would be getting to the edges of the leaves. The leaves would then dry and turn black. If you're unconsciously overwatering (you say that you aren't) to make up for the drying leaves, the new growth would be yellow from too much hydration. Are the blackening leaves dry, or mushy, or just the same texture as the green leaves? Over or underwatering can also cause root death, and in either case, root death can manifest itself in older leaves turning black, and new growth being yellowish.
posted by iconomy at 9:31 AM on June 4, 2006
I'd start by ensuring you're using a suitable watering practice (i.e. water at the base not at the tops, sprinklers and other automated systems can be pretty horrible about that).
Then move on to identifying nutrient deficiencies.
If possible post some pictures, full plant and macros of the affected growth if possible.
posted by Matt Oneiros at 9:56 AM on June 4, 2006
Then move on to identifying nutrient deficiencies.
If possible post some pictures, full plant and macros of the affected growth if possible.
posted by Matt Oneiros at 9:56 AM on June 4, 2006
Best answer: Oregano needs to dry out between waterings. The top two to three inches of soil should be dry before you water. Make sure you dig your fingers into the root ball and not just the potting soil. If the plant was originally planted in something like peat (as many nurseries do), and then you planted it in potting soil, the two media can dry out at different rates.
Here in summer-dry California, oregano (other than varigated and golden) does best in full sun, with minimal watering once established. This is why I suspect your oregano is overwatered. It's also an herb that is generally tolerant of nutrient poor soils, though mineral deficiency could be an issue, although I've rarely seen it.
One other thing to consider is salt burn- this occurs when plants in the ground or overfertilized, or plants in pots are fertilized but the soil is not thoroughly flushed each watering.
If those were my oregano plants: I'd do my best to cut back all unhealthy growth and clean dead material out from the center.
I'd then water the plants very deeply and give them a chance to dry out before the next watering. No fertilzer unless the new growth comes out yellow again, then I would use a liquid foliar feed containig chelated iron. If your water or soil is extrememly alkaline, that makes it hard for plants to take in iron, so a simple ph test would help determine this. I'd also considering moving them into full sun, if possible (this goes for the rosemary, too.)
Watering in the morning helps foliage dry during the day which minimizes fungal infections on the foliage. I personally have found that the gardens I work with that have overhead sprinkling actually have far fewer issues with pests and fungus due to the fact that the insects and spores are sprayed off during watering (this is in the Bay Area where water conservation, and therefore drip systems, are de riguer. Unfortunately, gardens with sprinklers are often healthier. Shrug). YMMV, due to differences in humidity, especially in the evening.
posted by oneirodynia at 1:11 PM on June 4, 2006
Here in summer-dry California, oregano (other than varigated and golden) does best in full sun, with minimal watering once established. This is why I suspect your oregano is overwatered. It's also an herb that is generally tolerant of nutrient poor soils, though mineral deficiency could be an issue, although I've rarely seen it.
One other thing to consider is salt burn- this occurs when plants in the ground or overfertilized, or plants in pots are fertilized but the soil is not thoroughly flushed each watering.
If those were my oregano plants: I'd do my best to cut back all unhealthy growth and clean dead material out from the center.
I'd then water the plants very deeply and give them a chance to dry out before the next watering. No fertilzer unless the new growth comes out yellow again, then I would use a liquid foliar feed containig chelated iron. If your water or soil is extrememly alkaline, that makes it hard for plants to take in iron, so a simple ph test would help determine this. I'd also considering moving them into full sun, if possible (this goes for the rosemary, too.)
Watering in the morning helps foliage dry during the day which minimizes fungal infections on the foliage. I personally have found that the gardens I work with that have overhead sprinkling actually have far fewer issues with pests and fungus due to the fact that the insects and spores are sprayed off during watering (this is in the Bay Area where water conservation, and therefore drip systems, are de riguer. Unfortunately, gardens with sprinklers are often healthier. Shrug). YMMV, due to differences in humidity, especially in the evening.
posted by oneirodynia at 1:11 PM on June 4, 2006
Response by poster: Wow! Thanks, all, for the informed replies. Here are some photos for you....
Zorba Rose Oregano
Mountain Greek Oregano (no blackness on this one)
Fertilizer
As far as the "rot" goes, the leaves are dry and crumbly where they blacken, and it always works from the outside in.
Does this look like overwatering?
posted by kaseijin at 1:52 PM on June 4, 2006
Zorba Rose Oregano
Mountain Greek Oregano (no blackness on this one)
Fertilizer
As far as the "rot" goes, the leaves are dry and crumbly where they blacken, and it always works from the outside in.
Does this look like overwatering?
posted by kaseijin at 1:52 PM on June 4, 2006
Response by poster: Oh, and the plants are in potting soil, fertilized lightly with the above fertilizer (which contains iron). I have been watering at the tops, about every 3-4 days, which I guess is bad?
posted by kaseijin at 2:01 PM on June 4, 2006
posted by kaseijin at 2:01 PM on June 4, 2006
Those actually look pretty healthy. The blackness looks like salt/fertilizer burn to me, not any fungus. Water deeply, allowing the water to run out of the pot and away, then put the pot back on it's saucer. Don't worry about watering from the top- you don't really have much of a choice, in this case. The new growth is normally a bit brighter green, if it doesn't darken with age then see my advice re: iron fertilizers.
posted by oneirodynia at 2:20 PM on June 4, 2006
posted by oneirodynia at 2:20 PM on June 4, 2006
It looks like aphids. I live in Houston and I used to live in Fort Worth and this is the worst time of year for those pesky bugs to lay their eggs. They lay their eggs on the the leaves and the leaves will curl and turn black around the edges. I had the same thing happen to my hibiscus and I found out too late before it attacked my whole plant.
Are there ants around these plants? Evidently, ants protect the aphids --who knew?
You need to pull off all the leaves with the black edges and turn your hose on "jet" and spray the he** out of your plants -- and focus underneath the leaves as well.
Then, mix 1 part dove soap and 2 parts water and spray your plant.
Hope that helps.
posted by oronico at 9:19 PM on June 4, 2006
Are there ants around these plants? Evidently, ants protect the aphids --who knew?
You need to pull off all the leaves with the black edges and turn your hose on "jet" and spray the he** out of your plants -- and focus underneath the leaves as well.
Then, mix 1 part dove soap and 2 parts water and spray your plant.
Hope that helps.
posted by oronico at 9:19 PM on June 4, 2006
Response by poster: Hmm. I don't know. I didn't see any aphids on the plants, but I'll double check. I sprayed all of my herbs not too long ago with an organic pesticide, too. =/
I did pull off all of the black leaves. I also flushed water through the pot like oneirodynia suggested, to clear up fertilizer burn. I'll give it a thorough once-over for aphids in the morning, and we'll see how it does. Thanks!
PS - could it still be aphids even if I don't find any adults crawling around?
posted by kaseijin at 9:48 PM on June 4, 2006
I did pull off all of the black leaves. I also flushed water through the pot like oneirodynia suggested, to clear up fertilizer burn. I'll give it a thorough once-over for aphids in the morning, and we'll see how it does. Thanks!
PS - could it still be aphids even if I don't find any adults crawling around?
posted by kaseijin at 9:48 PM on June 4, 2006
No. It's not aphids unless you see aphids.
Generally speaking, during the warmer months aphids are viviperous, meaning their offspring are born live (and often parthenogenetically, which means no male aphid is involved). Eggs are most often laid in fall.
Soap sprays can be effective, but as they are contact insecticides they only work if sprayed directly on the aphids. If you've blasted them off with the hose it's sort of pointless. It's also important for the soap to be about 1-3% of the solution, or you may injure your plant. Here's a good page about insecticidal soaps with dilution tables at the bottom. However, I generally just do the hose blasting, particularly on things I am going to be eating.
posted by oneirodynia at 12:22 PM on June 6, 2006
Generally speaking, during the warmer months aphids are viviperous, meaning their offspring are born live (and often parthenogenetically, which means no male aphid is involved). Eggs are most often laid in fall.
Soap sprays can be effective, but as they are contact insecticides they only work if sprayed directly on the aphids. If you've blasted them off with the hose it's sort of pointless. It's also important for the soap to be about 1-3% of the solution, or you may injure your plant. Here's a good page about insecticidal soaps with dilution tables at the bottom. However, I generally just do the hose blasting, particularly on things I am going to be eating.
posted by oneirodynia at 12:22 PM on June 6, 2006
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posted by ewagoner at 9:18 AM on June 4, 2006