Brown patches on Epipremnum. Any thoughts?

Hey folks, looking for some advice on the cause/remedy for brown patches on some of my Epipremnum leaves. They're only on a handful of leaves, but I'm worried they might become more of a problem. They feel thin and sort of elastic-y to the touch, if that makes sense, and only appear on the yellow parts of the leaves. The plant gets watered every 2-3 weeks after the soil dries out slightly, sits in a bright but sunless position on a tray of wet pebbles and is misted several times a day. If anyone has experience of this problem, whatever help or advice you could offer would be appreciated.

Paul.

Since it doesn't involve leaf tips or margins it's probably not directly related to a high level of soluble salts in the soil, under-watering, or over-watering, any of which would cause a drought response that would likely be manifest in lost foliage or burned tips/margins; which in the end leaves me to believe it's fungal and likely related to the frequent misting.

Al

I agree. I think a tray of moist pebbles will raise the humidity around the plant without the need for additional misting. Good air circulation is important as well.

I live in an area with a very humid climate and my plants stay outside almost year round. At times during the summer when it's extremely humid, and there's no breeze stirring, I can have problems with fungal infections on a couple of plants, so I use a small oscillating fan to give some air movement.

Thanks, guys. One of my plant books mentioned leaf spot as a possible culprit. Should I cut off the affected leaves? I'll quit with the misting and try to get more fresh air into the room. (It's just that it is getting really cold here in Scotland, making me worried about harmful, cold draughts from open windows and too-dry air caused by central heating)

'Leaf spot' in horticulture is like saying 'rash' in medicine - it's not very specific, but most leaf spot diseases are caused by fungal infection.

Misting does more for the grower in the sense that it fulfills our need to nurture or feel like we're 'doing something', but really is ineffective at raising humidity, which is the most common cause for cited for employing it. It can provide the conditions necessary for fungaluglies to incubate, as well as spread disease and insects from leaf to leaf or in some cases plant to plant.

If your plants are in a soil that allows you to water properly, soluble salts will not build up in the soil. High levels of salts makes it difficult for plants to absorb water, which is why leaf tips and margins burn. While low humidity can exacerbate the problem, it is almost never the root cause (re. common houseplants). We can usually always find the actual cause in the short list I left upthread (a high level of soluble salts in the soil, under-watering, or over-watering). Of these three offenders, we can usually trace over-watering and a high level of soluble salts to an inappropriately water-retentive soil.

Al

Thanks again for your input, Al. I'll stop the misting and see if things improve. Most of my plants sit on a dish of wet pebbles to raise humidity (I make sure that the water level does not come up to the bottom of the pot). Do you think this is beneficial or is it likely to cause more problems?

It won't hurt anything as long as there is no way for the water in the humidity tray to wick its way into the pot.

FWIW - A few winters ago, as an experiment I put a digital hygrometer in the branches of a bonsai tree in my living room & set the pot on a humidity tray with with 1/4" pebbles & water & about twice the surface area of the pot. The top of the pebbles were wet, so the evaporative surface was maximized. There was no fan on in the room, only normal convective air movement. The hygrometer registered only a .4% (4/10 of 1%) increase in RH.

Al

Does the plant get much potassium?

The plant was only bought a couple of months ago, and since it's pretty much winter here, I haven't been adding any plant food when watering. Do you think it is a potassium shortage? (When I do use plant food I just use BabyBio. I should probably start looking for something better?)

Tropical plants generally use more potassium than other nutrients. An all purpose fertilizer for tropicals should have a 2-1-3 ratio N-P-K.

A lack of potassium will cause burn on leaves.

Wow, the stuff I use is no where near that ratio. It's 10.6 - 4.4 - 1.7 NPK. Even the Miracle-Gro food I checked out on Amazon is 6 - 5 - 5 NPK. If yourself or anyone reading can suggest an alternative plant food I'd be grateful. Guess I've got a lot to learn about growing houseplants!

If your garden shop sells a Palm & Citrus fertilizer, that would have the right ratio.

Thanks for your advice. Will look for some (probably on-line, as my local garden centre is unlikely to stock it). The issue of feeding plants is more confusing than I would have guessed. As well as all the various ratios of NPK in different feeds, I have read opinions ranging from never fertilizing indoor plants to never stopping feeding, even over the winter months. Pretty confusing.

I have a somewhat different perspective, and I'll share why. Across the board, plants use about 3/5-2/3 as much K (potassium) as N (nitrogen). While there may be a very few tropical plants that use a greater amount of K than that, tropical plants as a group are no different than all plants as a whole. This chart shows average nutrient usages by plants:
Nitrogen has a value of 100 because it's the most used nutrient. Other nutrients are listed as a weight percentage of N.
N 100
P 13-19 (16) 1/6
K 45-80 (62) 3/5
S 6-9 (8) 1/12
Mg 5-15 (10) 1/10
Ca 5-15 (10) 1/10
Fe 0.7
Mn 0.4
B(oron) 0.2
Zn 0.06
Cu 0.03
Cl 0.03
Mo(lybdenum) 0.003

If you look down to K, we see that plants use between 45-80 parts of K for every 100 parts of N, an average of about 62% or 3/5 as much K as N. Even palms do not use more K than N, but fertilizer packagers have created willing buyers of 'Palm Fertilizer', just as they have for 'Bloom Booster' formulations, which in some cases supply more than 30 times as much P as the plant can use (in relation to N).

It's possible that your plant is deficient in K, but it's probable that there would be other deficiencies as well if it is - especially since bark and peat-based soils are generally high in P and K to begin with (again in relation to N).

The commonly found fertilizer formulations like MG or Peters 24-8-16, MG 12-4-8, Dyna-Gro's Foliage-Pro 9-3-6 supply nutrients in a ratio very close to that which plants use (closest commonly available), and supply all the K your plant needs in relation to N.

That said, I'm doubting that you would have received a plant 2 months ago that could have developed a K deficiency so severe it produced the symptoms shown in the picture in that short of a time. Symptoms of nutritional deficiencies that severe usually lag the onset of the deficiency by a considerable amount of time. We can probably assume the plant was well cared for (well fertilized) at the greenhouse where it originated, so it's doubtful the plant could develop a deficiency that severe so quickly AND have time to develop the symptoms shown in so short a time.

My bet is still on something cultural, probably the misting.

BTW, Paulie - how often and how much you should/can fertilize should partially take into consideration where the plant is in the growth cycle and how much light it's getting, but the primary determining factor comes by having to work within the limits of your soil and watering habits. You can fertilize at low doses every time you water, all year long, if your soil is fast (draining) enough to allow you to water properly. Watering properly means watering to the point where at least 10-15% of the total volume of water applied exits the drain hole. This flushes accumulating salts from the soil with every watering and ensures that nutrient levels are low enough that the plant easily takes up water, yet high enough that there are no nutritional deficiencies - the ideal state of nutrition.

Al

Thanks, Al, for taking time out to explain things so clearly. I'm going to change my plant food to MiracleGro, and I'm already making sure to water my plants in the way you suggest, flushing the compost thoroughly (and cutting back on the misting). I'm sure it will mean fewer problems with my plants.

Paul.

OK, good - but please remember that it takes a well-aerated soil to water properly. I wouldn't want you to water to run-off when using a heavy soil and have your plants develop root issues because of the anaerobic (airless) conditions in the soggy soil. ;o)

Al

The soil seems pretty good in most of my plants, the water runs through pretty quickly. I have one or two where I have to water in small amounts to let the water sink into the soil, although I'm guessing it's more a case of the roots filling the pot rather than heavy soil. Also, I've been inspired by a few posts, including yours, into mixing up my own soil for next spring's repotting. I can't find all the ingredients which you use but I've just bought some perlite and I'll get some bark also (does it matter what kind?).

Yes - hardwood bark, 'wood or forest products', 'wood chips' or ground heartwood/sapwood products should be avoided for multiple reasons. Conifer bark is rich in suberin and lignin, both of which make it difficult for soil organisms to cleave the hydrocarbon chains in the bark (IOW, it breaks down very slowly) so you don't have the problems with nitrogen immobilization (ties up N because the soil biota out-compete the plant for available N) and extreme spikes in pH during the composting process. I prefer pine or fir bark because it's very easy to get, but I have friends that have used redwood and hemlock bark with good success, too.

You may have a calcined clay product like Turface available to you there called Montmorillonite.

Al

Just ordered a couple of bags of pine bark chips on eBay. Thanks again for all your help and advice.

Size is important, so keep that in mind when you make the soil. If the pieces are too large, you can reduce the size by setting your mower with the catch bag in place to its lowest setting & running the bark over with it. The small pieces collect in the bag.

Al

Maybe that's what I need to do, too. Honey, will you mow this for me? Tee hee.hee...

Epipremnum pinnatum is a very tough tropical plant. Here it is a weed. It is not very particular to soil, as it is a hemiepiphyte; so your soil & bark choices are of little consequence. The more root-space you give it will allow a larger plant though.

By giving the plant a high nitrogen fertilizer, will be good for the leaves, but not the stems, which is how this plant carries itself.

Treating tropical plants the same as temperate annuals will be a mistake.
High nitrogen is good for Aroids such as Colocasia & Alocasia as their main growth is in leaves., but it won't be good for Epipremnum.

Climbers & vines such as Epipremnum & Philodendron need much more potassium than your normal temperate plant. This is the case with many tropicals that require strong stem growth. You will see the deficiency show up in the leaves, which may be the case with your plant.

A good article about potassium nutrition is found in Broschat & Meerow. 2000. "Ornamental Palm Horticulture". University Press of Florida. Look up Chapter 4 "Mineral Nutrition of Ornamental Palms".

Giving all plants a high nitrogen diet in general is wrong. If you do that to tomatoes and peppers, you won't get anything but leaves!

It is best to care for plants on an individual basis, rather than treat them all the same.

Certainly, the fertilizer I've used before has a very low potassium ratio, although as Al pointed out, my plant is fairly new so the problem is probably my doing (too much misting rather than potassium deficiency) as it was in good condition when I received it. However, I've just bought some Miracle-Gro plant food which has a 6 - 5 - 5 NPK, which seems closer to the "ideal" mix and which I'll be using from now on.

Regarding the bark, it is Golden Pine Orchid bark, so I'm assuming that it's already the correct size for potting plants/soil mixing. In any case, the lawn mower has been stowed away until the grass needs cutting again, probably March-April, here in Scotland. I'm definitely not getting it out again until then!

By giving the plant regular feedings you can avoid deficiencies (the plant will take what nutrients it needs).

As the plant is a hemiepiphyte, it is used to getting some of it's nutrition in run-off (tea) from other plants. You can replace this with foliar feedings.
Use one teaspoon per gallon of water of your Miracle-Grow, and mist your plant with it.

Misting the plant should not cause any problems if it is well ventilated. The plant does extremely well here in rainforests that get more than 100 inches of rain per year and it is used to being wet all the time.

The only time I have seen plants that get the leaf burn like yours, is when they are grown indoors and don't get enough nutrition.

Good luck with your plant!

Aloha, Dave

Thanks, Dave and Al, for all your useful advice.

I think the soil you choose for any container plant is of considerable importance. In many cases, it makes the difference between whether or not your plant even has the chance to grow at near its genetic potential. As for the bark, there are many types of bark that are wholly unsuited to use in container media, hardwood bark, e.g.

That any fertilizer has a higher N content than either P or K does not make it a high N fertilizer. As noted, all plants use more N than either P or K, so it should be considered normal for the N content to be higher than P or K. Most fertilizer manufacturers of soluble fertilizers make 1 or more formulations in the 3:1:2 RATIO that they label as all-purpose fertilizers. It's not an accident that these fertilizers supply NPK in almost the exact same ratio that plants utilize them in.

Good articles regarding greenhouse plants and the fertilizer ratios that are used to maintain them are found in dozens of texts. Plant Production in Containers II by Dr Whitcomb (practically a bible), Water Media and Nutrition for Greenhouse Crops by Dr W Reed, the Ball Redbook on Greenhouse Crop Production Vol II, Growing Media for Ornamental Plants by Handreck and Black, others, all support what I mentioned about nutritional wants. In most cases, greenhouses will fertilize at 3:1:2 ratios unless they purposely wish to limit vegetative growth to make plants bushier, then they will purposely limit N to a 2:1:2 ratio.

Not that it is important, because we're not talking about tomatoes and peppers, but I usually fertilize my young containerized tomatoes and peppers with 3:1:2 ratio fertilizers, or even 3:1:1 (30-10-10 MG) until the plants have a fair amount of photosynthesizing machinery (leaves) in place, then I switch to a 2:1:2 ratio fertilizer to limit vegetative growth so the plant is forced to direct photosynthate to fruit production rather than foliage. It's a very good strategy to build lots of foliage and then force the plant to direct the larger volumes of photosynthate made available by that foliage to fruit production.

I sort of agree with the idea that plants should be treated as individuals, but grouping all tropicals under the heading of K lovers kind of goes against that idea, which is what prompted my response to begin with. I also offer other good reasons why I think a K deficiency would be unlikely as a singular concern.

Take care.

Al

Would it be a good strategy to occasionally switch to a different ratio? I mean, lets say I use fertilizer at about 10% of recommended strength at most waterings (just occasionally use plain water). One week use 30-10-10 acidic, next week 24-8-16 gp, the following week something, and then just plain water sometimes for a nice flush. I mean sometimes a dog pees on a bush, sometimes a squirrel or bird leaves excrement, leaves break down, worms leave tunnels of black gold, etc. Is that a waste of brain energy, or would it have a benefit?

Not really. If you're using growth as the measuring stick, which is the increase in the mass of the plant, the ideal situation is to have all the nutrients a plant uses, in the soil, all the time, at the lowest concentration that will ensure there are no deficiencies, or slightly above.

I would reserve the flush for soils that are too water-retentive to water properly. Those soils that are fast (draining) enough to allow you to water to saturation and then beyond to flush the soil with every watering don't need additional flushing. In fact, if you happened to be fertilizing at minimum doses, so that you were on the borderline between nutrient levels that were sufficient/deficient, the water only application could be counter-productive.

It probably takes a fair working knowledge of the relationship between your soil's drainage characteristics, your watering habits, and fertilizer solution strengths to figure out exactly what I meant, but you can hardly go wrong fertilizing plants in a fast soil with frequent low doses of a fertilizer that has all the essential elements supplied in as close to the ratio as the planting uses them as possible.

Al

Thank you. I am working on the understanding soil structure and watering. You guys are really great :). So what do you do for your acid lovers, like orchidacea? Is that where you do a dash of vinegar in the mix?

I don't know much about the peculiarities of orchids, so I'll leave that answer to those more expert than I in that area, but I'll get technical first. If you have questions, you can ask & I'll answer, but I'll leave a shorter answer at the end if you want to just skip to that.

The fact that different genera/species of plants grow in different types of soil where they are naturally found, does not mean that one needs more of a certain nutrient than the other. It just means that the plants have developed strategies to adapt to certain conditions, like excesses and deficiencies of particular nutrients..

Plants that "love" acid soils, e.g., have simply developed strategies to cope with those soils. Their calcium needs are still the same as any other plant and no different from the nutrient requirements of plants that thrive in alkaline soils. The problem for acid-loving plants is that they are unable to adequately limit their calcium uptake, and will absorb too much of it when available, resulting in cellular pH-values that are too high. Some acid-loving plants also have difficulties absorbing Fe, Mn, Cu, or Zn, which is more tightly held in alkaline soils, another reason why they thrive in low pH (acid) soils.

Media pH in containers is no where near as important as it is in mineral (garden) soils. Mineral soils in general hold nutrients much more tightly than the highly organic soils we grow in. If you'll consider: Even the gritty mix I often use is still highly organic at 2/3 inert ingredients: 1/3 (33%) bark as compared to the soils in gardens with an extremely low organic component (usually

I don't know much about the peculiarities of orchids, so I'll leave that answer to those more expert than I in that area, but I'll get technical first. If you have questions, you can ask & I'll answer, but I'll leave a shorter answer at the end if you want to just skip to that.

The fact that different genera/species of plants grow in different types of soil where they are naturally found, does not mean that one needs more of a certain nutrient than the other. It just means that the plants have developed strategies to adapt to certain conditions, like excesses and deficiencies of particular nutrients..

Plants that "love" acid soils, e.g., have simply developed strategies to cope with those soils. Their calcium needs are still the same as any other plant and no different from the nutrient requirements of plants that thrive in alkaline soils. The problem for acid-loving plants is that they are unable to adequately limit their calcium uptake, and will absorb too much of it when available, resulting in cellular pH-values that are too high. Some acid-loving plants also have difficulties absorbing Fe, Mn, Cu, or Zn, which is more tightly held in alkaline soils, another reason why they thrive in low pH (acid) soils.

Media pH in containers is no where near as important as it is in mineral (garden) soils. Mineral soils in general hold nutrients much more tightly than the highly organic soils we grow in. If you'll consider: Even the gritty mix I often use is still highly organic at 2/3 inert ingredients: 1/3 (33%) bark as compared to the soils in gardens with an extremely low organic component (usually less than5%).

Fertilizers affect media solution pH and make it easier/more difficult for certain types of plants to extract nutrients from soil solutions. Often, the plants themselves add ions to the solutions to actually change solution pH and make it easier for the plant to take up other ions. The fertilizers we would want to use for 'acid-lovers' will have an acidifying effect due to the ammonium nitrogen content. Fertilizers that form acids will be high in ammonium, ammonia, and urea. During nitrification, ammonium is converted to nitrate in the media, and in the process H is released which lowers pH. Plants also secrete H into the media whenever they absorb ammonium.

Fertilizers containing nitrate in the form of calcium/potassium/magnesium/sodium nitrate all tend to cause an alkaline reaction and raise container solution pH.

Although the most important factor in where media solution pH will fall is the alkalinity of the irrigation (which includes the fertilizers added) solution, it's not the only factor. We need to not only consider the fertilizer, but also the pH of the medium components, the liming materials used in the medium, and the pH/alkalinity of the irrigation water before adding fertilizers.

The short answer is: Media pH is not as important to container culture as mineral soil pH is to gardening, so it's probably less of an issue than it's made out to be. If I wanted to use a fertilizer for plants (I'm not sure about how orchids tolerate various fertilizers because I grow only a few terrestrial hardy orchids, so take this with a grain of salt as it applies to orchids) that need a low pH so they can manage nutrient uptake, I would use those fertilizers that derive their N from urea. 30-10-10, 24-8-16, and 12-4-8 are all MG products in the 3:1:2 ratio that derive their N from urea and are acid-forming fertilizers, even though 30-10-10 is the only one MG advertises specifically for acid-lovers. If the water I use for irrigation was high in alkalinity, I would probably also add enough white vinegar to it to lower the pH to around 6, which would halt the normal upward creep in media pH as it ages. I employ this strategy in the winter for plants I over-winter under lights.

Oh man - I didn't even realize we'd strayed off the OT. Sorry PW. I hope it's ok, seeing how the conversation sort of got steered in the direction of nutrition.

Al

Sorry for off topic. I probably ask too many questions, that's what I heard as a child, anyway :). I am going to go start a thread to get the dirt on dirt.

You're right that all tropicals do not use more potassium than nitrogen, but a large amount of them do.

Such as, all Palms use more potassium than nitrogen. Citrus and other tropical fruit trees use more potassium than nitrogen. Vines and climbers such as Epipremnum pinnatum, use more potassium than nitrogen.

While greenhouses may force tropicals with nitrogen, that is not how they grow in nature.
Forcing tropicals with nitrogen may produce a luxury of foliage on a young plant to make it look good for sale. This also will cause stem lodging and deficiencies in other nutrients such as potassium.

I guess we'll just have to agree to disagree. ;o)

Al

Easily done Al!

Aloha, Dave

We are all after what works for us, so different views will help each individual person find that for themselves. Thanks to everyone that is willing to share their point of view and help us learn :).