Why do plants turn yellow?

[Micromegas]

In my garden some of my succulents and cactus are turning slightly yellow. The soil is unfortunately fairly heavy clay (in a wind-exposed area), but has been worked considerably with mulch, horse manure and occasionally potting soil has been added. Any thoughts on why some plants are turning yellow... or even why plants/leaves turn yellow in general? Some of them are newly planted, so perhaps they are settling in, but I have the feeling they are missing something... Any ideas?

[planthelper]

waterlogged?

my feeling is that there is something wrong with the roots.

yellow normaly means nutrient (N) defiecency but i guess the roots are damaged and thats why the poor thing can't uptake nutrients and get's yellow as a result. proly the tip is still a bit green, because that is wher the cacti moves it's stored nutes in a desperate aim to survive...

i would dig them out and inspect the root enviroment.

than either pot into pottingmix or a different location, maybe you have to cut, calluse and re grow roots.

my instincts tell me that you might have created what is called a "ph's stupid friend disaster", in this instance my friend replanted all my happyly growing pedros into a waterlogged position wher they fast turned yellow and died.

you would have been proly better off, not to mix pottingmix or topsoil into the clay!!

see what might have happend is you diged holes into clay and filled them with a medium totaly different to clay, so all the water just stays in those holes and as such leads to root rot!!

if you would have not mixed potting mix into it, chances are they would still be green.

plant them out onto a freedraining position, like on top of a slope, or create a mound where onto you can plant them your cacti.

differnt mediums produce what i call waterlines, caused by different viscose and osmotic properties?!

[foolsbreath]

It is a sign of depresion

Treat with love and tenderness

[Rev]

dig a trench to at least 300mm to the side of the spot and install 100mm drainage agpipe backfilled with blue metal ( or whatever) and drain off site or to weherev irt needs to go

check pH and use lime (if acid) or gypsum (if not) to open up clays. it will take time

i suffer with high watertables too and sodden clays seasonally

agpipe is gods own invention

[foolsbreath]

Yeah great advice rev, If only we could get all irrigators to do this, and reticulate there would be no water problem in australia!!

[Micromegas]

Thanks very much, helpful responses indeed... I'll have to go out and investigate the situation tomorrow. I'm not sure they could be waterlogged. Though the soil is heavy, there hasn't been much rain

Another thing that has been plaguing me are some san pedro cuttings I planted. They look fine, have been in the ground for about a month and have remained fairly dry... but I didn't wait for them to callous over before planting is it necessary to remove them and allow them to dry out before re-planting?

Thanks for helping out. It seems there is no end of things to learn about gardening!

[Rev]

if they arent rotten now then they have probably rooted

id leave them alone

[kakti]

Too much direct sunlight..?

[Micromegas]

What are some indications of rot in cacti?

[indigo264nm]

Any thoughts on why some plants are turning yellow... or even why plants/leaves turn yellow in general? Some of them are newly planted, so perhaps they are settling in, but I have the feeling they are missing something... Any ideas?

Nitrogen (N) deficiancy is often the main cause of yellowing, but also the way in which the yellowing is occuring will provice insight. The veins staying green and the the rest yellowing (interveinal chlorosis) can indicate a variety of different deficiencies (Fe, Mg, Mn) depending on how the yellowing is forming on the leaf.

If the leaves are browning as well and are looking like they are dieing it could be anything from insect damage, incorrect soil conditions for the plant, incorrect sun exposure for the plant, incorrect temperature for the plant (winter coming ), incorrect humidity for the plant, incorrect pH, salinity and a whole list of things including diseases.

Can you tell us what other plants are being affected??? It could just be seasonal, or they could be getting too much light.

Also for the heavy clay part, as Rev said, you might want to consider adding in gypsum and turning the soil very thoroughly before you next plant anything in... checking pH is definitely a good idea.

Also check to see if the soil repels water instead of absorbing it which may happen after clays have dried out.

The agpipe idea is very effective in such cases, but luckily such has never been an issue for me living so close to the beach.

Always wait for the pedro to callous over hehe .

[teonanacatl]

check your pH, most times with plants in the ground its not a nutrient deficiency but a pH problem.

[indigo264nm]

What are some indications of rot in cacti?

Never really had that problem but try digging out some soil at the base, get down close and have a good old sniff. You should be able to smell something funky.

[Micromegas]

Wow, thanks again. Had a good look today and everything looks reasonably well. I guess what I'm talking about with the yellowing is sort of just a fade in colour from deep green to a yellowy-green which has happened on a few pedros and an aloe vera plant. The pedros I am sure are reacting to the direct sunlight, since the cuttings came from a huge, shaded mother plant. Other trichocereus cacti have also yellowed just slightly after being moved into direct sunlight. I wish I had known about the callousing-over part a few weeks ago, but the pedros I planted last year went in fresh and grew well (also in direct sunlight)... and these ones look fine at the moment (these also faded gradually from dark green to light green)... the aloe vera plant was recently planted and has improved in the last couple of days after some watering, but its tips are still yellow.

Of more worry is the Faucea succulent which has turned yellow all over, and a jade tree whose smaller leaves yellow and drop off while the other leaves look fine. It certainly wouldn't surprise me to find some nutrient deficiency. But really, for the most part, it might be too early to tell what will survive and thrive since I only started the garden six weeks ago.

As for working the soil, i've been gradually improving at that also while the area increases. I've used quite a bit of gypsum and horse manure as well as organic mulch. The rain last night drained away well but there's no hiding the fact the soil is/was terrible. If I tried to dig into it with a spade I could get in only two or three inches (sometimes one!) before the mattock was required. It's been a lot of hardwork.

How does one go about checking the pH?

Thanks for answering my tedious question, I'm sure they won't be the last!

[teonanacatl]

with a pH test kit available from your nearest nursery:)

[Rev]

pH is fundamental

most garden soils are 6.5-7

but if its not you need help

sulphur, iron sulphate, aqueous vinegar and compost for alkaline soils

lime , dolomite and calcium fortified compost for acid soils

Edited May 1, 2006 by Rev

[Alice]

check your pH, most times with plants in the ground its not a nutrient deficiency but a pH problem.

also pH problems can be the cause of nutrient deficiency/toxicity

eg some elements precipitate out of solution at high pH as they may form insoluble hydroxides, so they are essentially unavailable to the plants, which could cause a nutrient deficiency.

and at low pH these hydroxides may dissociate and release the element back into the solution, possibly causing nutrient toxicity.

but clay has a surprisingly large surface area for ion exchange, so clay soils can also buffer against these changes too.

test the soil with a kit as suggested and adjust if necessary to the plants optimal range. if you're looking at a nutrient problem as opposed to water/sun/etc then adjusting the pH usually makes the plants much more happy.

also try and get a chemical pH testing kit as opposed to a probe type, they tend to be more accurate.

[planthelper]

now that you say that the soil is very hard, i tend to believe that it's very hard for the roots to develope in this type of condition, the result is the same, no healthy roots, no uptake of nutrients, resulting in yellow apereance. haven't you got better soil, somewher else in your garden? you could use some steel to probe all over your place, till you find soft soil...

if all is heavy clay, use gypsum as said and construct raised beds, after loosening up the heavy clay as much as possible. you have to dig over the whole area. just digging holes and re filling them with enriched soil, will pose some risks. after heavy rains all the water will collect in there without draining off.

i gave my cacti the best spots (on a nice slope which aids drainage) in the garden, they fully deserve them.

[Micromegas]

Thanks planthelper, if only I had thought about this before planting! Gradually I have been realising my mistakes and working backwards. I certainly should have worked the whole area first... but I didn't, so now I have to work backwards. Things are steadily improving. I have improved the soil quite a bit overall with gypsum, mulch, manure and topsil... but the plants I put in at the beginning are already firmly in the ground in a situation such as you describe, sitting in enriched soil but with clay all around. The san pedros however were put in raised, sloping beds, or in pots. I live south of Adelaide, in a fairly dry spot (490mm/year), which gives me hope for the rest of the plants ranging from cereus and trichocereus cactus (and others requiring I.D), various aloes, opuntia species, a number of succulents and agaves, and a few natives and other shrubs. I had two san pedros planted in a bathtub with no drainage at all last year and they grew at least five times their original size... I should blame them for encouraging me!

So what to do about it now? Just keep working on the soil? Most of the plants appear relatively happy... I certainly encourage them to grow! They seem to enjoy being planted in a community. I can't imagine just one plant suffering my in-experienced gardening onsluaghts coupled with clay and occasional high winds!

But to add to the problem I'm leaving the country for seven months soon... I'm hoping the plants will get through winter and establish themselves in the great spring weather and await my return in summer! I guess that was the reason I went with cacti and succulents... that and my reverence for such remarkable plants!

I did test the soil today with a probe and it came up as pH 7 which MUST be a lie. I will use a chemical tester tomorrow.

Thanks again for the responses. I can imagine this hobby becoming an obsession (too late). Probably best I leave the country...

BTW, today I went to nursery and next door was a vacant lot with an awesome cactus growing in it. I asked the shopkeeper if it was their lot and she said yes, and after i'd paid for my purchases she let me take a few cuttings. These cuttings are about 30cm around and 30 in length and the plant looks like a really fat T.spachianus (spine and colouration), but it was growing in big clumps and doesn't have a woody spine in the centre. I'd love to post a photo but my camera's broken. Any idea what it could be?

Long post, i know... thanks again.

Edited May 2, 2006 by Micromegas

[planthelper]

hmm, i wasn't aware that your location is that dry, but that means that my concerns don't have that much merit. wish you happy travells and i am sure you can't belive your eyes when coming back.

[Micromegas]

Yes, quite dry...

Checked the pH today with a chemical test. The first place i checked came up between 6 and 6.5... then I walked twenty metres and the pH was 7.5! I guess that's just the way it's gonna be. At least the pH wasn't too extreme either way.

Also pulled up one of the pedros to have a look. The bottom was dirty (no surprise there) and once washed off was still brown/black (from the soil I presume). The column is firm and looks healthy, there was only the pleasant smell of dirt and cactus, and there even seemed to be some minor root growth (it's been in the ground for four weeks maybe) - little shoots coming from around the base of the spine about 3-5mm long.

Does this sound OK? Doing everything a SP should be doing?

[Rev]

sounds good

Organic matter is a great buffer for most soils

it remedies heavy soils, sodic soils, alakline soils, acidic soils, skeletal soils, asndy soils, heavy clay soils etc etc.

but in a low rainfall area you nee attention to detail

OM should be WELL composted. Breakdown needs awter and too much mulch and raw OM in the soil profile robs the soil of nutrients AND water

i would use mineral suppements in gardening

(natural gypsum, lime , dolomite, elemental sulphur, rock phosphate)

well rotted organic true compost, decomposed cow manure and seaweed

inorganics like super and urea ( if kickstarting 'Dead' soils), but generally only potassium sulphate is necessary. as ol' pete cundall says KSO4 is bloomin marvelous ;)

the theory is that arid area soils are generally low in OM.

why buck natures example.

high debris IN arid soils kills plants by robbing nutrients and water in decomposition

HOWEVER

if you can irrigate use a mulch of straw or chips or whatever and drip irrigate through it. but do not dig in the high carbon mulch. let it staty moist ast the mulch soil interface and let teh fungi break it down and mineralise it fr the plants

this a most successful strategy on any sandy soil and in arid areas

it pays to scarape away the mulch during the wet season s and replace it in the dry.

In very arid areas use only very decomposed organic materials, inorganics and heavy ROCK mulches

the larger the stone the more thermal mass it has to resist heat (stays cooler underneath) and hold heat ( resists frost at night)

Edited May 3, 2006 by Rev