Yellowing

[Pearcy001]

Hi Daluke,

How long have you been watering 3 times a day for? Also how much sun does it get? 2-3 times a day watering seems a little much for a pine to me, in saying that I'm definitely no expert on pines so ignore me until others chime in. I was under the impression it was better to keep them a little on the dry side? Maybe excess water could be causing the yellowing?

Cheers,
Pearcy.

[Daluke]

It gets full sun. Probably 8 + hours. I've been watering 3 x a day when temps are 30 degrees +. The other pines seem to be growing mad with the water and sun. They get fed with liquid ferts once a week / fortnight.

[evan]

Could you also take a photo of the base of the needles that are yellowing? One that shows their positions on the branch.

[Daluke]

I'll have to do it when I get home tonight. Interestingly it doesn't seem to be getting worse or spreading. I only noticed when recently pruning the new growth to ramify. I've been treating it the same as my other pines - as said regular feeding and watering. The only time I've cut it is a few weeks ago when I took off the new growth to induce a second flush.

[treeman]

Saying that blackening of the tip on ANY species of plant is a sign of problems is akin to saying that having a body temperature of less than 37C in ANY species of animal is equal to ill health. How about cactus spikes, they're leaves with black tips.

Speechless on that one..

You can't compare pines with broadleaf plants, they have completely different mechanisms in their internal systems for energy and water management and transport.

Care to share those differences?

While blackening on a maple leaf indicates some problem, blackening of the tips on black pine needles seems to be a natural process for old needles

Not on mine. The tip goes brown (on all of them)

Your definition of "natural aging" still doesn't apply to every single plant.

Sure it does. Iv'e been growing thousands of species of plants for a long time. From grasses to perennials to orchids to shrubs to trees. The ageing is always the more or less the same. Any sign of black indicates an unnatural problem mostusually with the roots. Whether it be from too much water, a build up of salts in the leaf tip, or a fungal issue.

There are too many variables to consider with why chloroplast degradation is occurring at the rate it is. While your trees may be going straight from yellow and then brown, I think in Dalukes tree the process is happening at a different rate because of these variables.

What variables?

I've got many examples here of trees with the exact same old growth habits, but my phones photo size is too big to upload right now.

Well when you can, I'd like to see what you mean.

[evan]

If you didn't know that cactus spikes are simply modified leaves, I think you probably need to hit the books Treeman. Leaf morphology is an extremely complex subject. Colour expression, as we know, is the result of chloroplast concentration and degradation, hormones and associated chemicals with the various stages of leaf degradation (for example the yellowing of leaves prior to leaf abscission is the result of chlorophyll breaking down to form carotenes). For some species expressing blackness in the leaf can serve many different functions such as defense, and usually occurs due to lignification, for example cactus spikes are simply modified leaves. Problems in xylem and/or phloem transport chains, heat over-exposure, along with simple things like insect attack can also cause blackness (or what it really is, cell death) in leaves.

While for most broadleaf varieties, black leaves are associated with cell death, and hence infection or environmental stresses, I believe some pine needles naturally develop a black tip as a result of slower leaf abscission due to the inherent differences in internal biology between conifers and broadleaf species.

The main difference between conifers and broadlead is that conifers do not have xylem, but, instead use tracheids. While the xylem is made of many smaller cells, which are perforated and allow easy water exchange in and out, tracheids are one single lignified cell that is imperforated (meaning that water exchange can only occur at certain points between cells).

The other huge difference (and this is the more important one for what we're discussing) is the sap systems of conifers are far more important in conifers than it is in other species. As we all know from working with pines, the ability for pine resin to remain as a liquid for much longer than other plant saps are capable means that sap systems in pines remain much longer within the plant and/or leaf. This is one of the reasons that expression of illness in conifers usually takes a much longer time than broadleaf varieties (usually a difference of weeks), because the internal rate of degradation is much slower than broadleaf.

This slower rate of leaf abscission is also what cause the gradual yellowing of pine needle. This rate can be affected by many different factors, from temperatures, hormone levels, light availability, water avaliability.... pretty much any environmental factor that affects plant growth. So for each persons microclimate, the specific factors influencing internal plant mechanisms is completely different.

On top of this there are many other factors that we simply don't know enough about yet that cause plants to express various physical traits such as genetics and viral infections for example.

SO generalising leaf blackness being caused by root, and root problems only doesn't help in trying to determine the actual cause of blackness in leaves. Which in this instance is normal leaf aging for pine leaves. If you have anything else you'd like me to explain to you Treeman, I have all the time in the world

(Ps. If you want to know where my information comes from, I'm currently doing a Bachelor of Agricultural Science)

[Daluke]

I hope this clarifies

[treeman]

I hope this clarifies

A much better pic. The other looked like black tips to me (must be my eyes )
Anyway pretty normal BROWN tips there. Nothing to worry about. (even though they really should not be there this time of year)

[treeman]

If you didn't know that cactus spikes are simply modified leaves, I think you probably need to hit the books Treeman.

Not only did I know that I have a collection of several hunred cacti. Many with black tipped spines.

Leaf morphology is an extremely complex subject. Colour expression, as we know, is the result of chloroplast concentration and degradation, hormones and associated chemicals with the various stages of leaf degradation (for example the yellowing of leaves prior to leaf abscission is the result of chlorophyll breaking down to form carotenes)

Irrelevant to this discussion

For some species expressing blackness in the leaf can serve many different functions such as defense, and usually occurs due to lignification

Show me an example

Problems in xylem and/or phloem transport chains, heat over-exposure, along with simple things like insect attack can also cause blackness (or what it really is, cell death) in leaves.

True. Cell death expressed as a black colouring. In other words (my words) unnatural or external influences such as pathogen or insect attack at the roots or the leaves directly. Sunburn, chemical burn, etc.

While for most broadleaf varieties, black leaves are associated with cell death, and hence infection or environmental stresses, I believe some pine needles naturally develop a black tip as a result of slower leaf abscission due to the inherent differences in internal biology between conifers and broadleaf species.

Brown tip not black.

The main difference between conifers and broadlead is that conifers do not have xylem, but, instead use tracheids. While the xylem is made of many smaller cells, which are perforated and allow easy water exchange in and out, tracheids are one single lignified cell that is imperforated (meaning that water exchange can only occur at certain points between cells).

Lignified cells are brown

The other huge difference (and this is the more important one for what we're discussing) is the sap systems of conifers are far more important in conifers than it is in other species. As we all know from working with pines, the ability for pine resin to remain as a liquid for much longer than other plant saps are capable means that sap systems in pines remain much longer within the plant and/or leaf. This is one of the reasons that expression of illness in conifers usually takes a much longer time than broadleaf varieties (usually a difference of weeks), because the internal rate of degradation is much slower than broadleaf.

Again completely irrelevant to this discussion.

This slower rate of leaf abscission is also what cause the gradual yellowing of pine needle. This rate can be affected by many different factors, from temperatures, hormone levels, light availability, water avaliability.... pretty much any environmental factor that affects plant growth. So for each persons microclimate, the specific factors influencing internal plant mechanisms is completely different.

Yes agreed. But what has that to do with blackening tips?

SO generalising leaf blackness being caused by root, and root problems only

Never said ''only'' What I said was that blackening (as opposed to browning) always indicates an unnatural cell death. (assuming we are calling pathogenic or chemical stresses unnatural)

If you have anything else you'd like me to explain to you Treeman, I have all the time in the world

You haven't explained anything or shown me any reason to suggest what I'm saying is wrong. If you can show me an example of blackening tissue on a plant which is caused by ageing please do. In all the years in horticulture, I cannot think of a single example where this occurs. If it does, it must be extremely rare.

(Ps. If you want to know where my information comes from, I'm currently doing a Bachelor of Agricultural Science)

That's very nice.
Please note! So you're not confused, leaf damage (not ageing) caused by many of the issues mentioned in this thread is usually expressed as BROWN coloured tissue.

[Boics]

Robust discussion lads!
Interesting. Fwiw i wouldnt be too worried!

[Daluke]

I'm sorry I didn't mean to divide the seas. Everything has been quite educational. I'm curious though - if it had a root problem, what would the needles be like?

[anthonyW]

Mmm that sounds like a lot of water my friend whats the medium and how long have you been doing that for and on that particular pine for if you don't mind
Anthony

[Daluke]

I water heavily when it's hot (we've been having 35 degree plus days).

[treeman]

I'm sorry I didn't mean to divide the seas. Everything has been quite educational. I'm curious though - if it had a root problem, what would the needles be like?

Typically, in my experience, root damage due to overwatering, (and subsequent fungal attack) new growth slows right down and eventually stops. Needles become pale and limp. They eventually go yellow and may or may not develop black tips or patches then either fall off or remain on the pine and brown. This is the most common problem and I've had it happen to 2 trees this summer. A white and and a black. Regardless of the air temperature, the tree should not be watered excessively.
Better to spray the leaves frequently than to constantly drench the potting medium.
With excess fertilizer, you often get yellowing needles (or leaves) and black or brown tip but the needles remain firm for a while until the roots are damaged and attacked by pathogens (if they are)
That is what I have observed anyway.

P.S (for evan) I did manage to find a plant where natural ageing causes blackening. It's a native orchid. Sarcochilus falcatus.
The old leaves and flower stems do not go brown but jet black!....So there's one...

[evan]

Sorry to get a bit riled up about the topic treeman. I think the semantics in our responses and the way I was interpreting your responses may have gotten a tad mixed up, and I tend to get a bit defensive when it comes to matters of science and sometimes go on a tangent.

I completely agree with what you've said about fungal infection caused by root damage as a definite cause of black tips in some instances. But also in my experience I've observed that some black pines will develop black/brown tips by natural aging as well. Particularly in 2 to 3 year old needles, and that rather than drop when they've turned brown, they'll do so when they've completely yellowed instead.