[James Kilkelly]

Yellow leaves on plants, causes and cures.


Iron deficiency on a Rhododendron showing up as yellow leaves, with leaf veins remaining green. , photo / picture / image.


"God you look pale, are you sick?" This concerned phrase is usually uttered human to human, if one of the individuals looks a tad off colour. However, where I am concerned, I will often offer the comment towards a particular shrub, perennial, or tree that has lost its green splendour.

Autumn colouration aside, when a plants normal green leaf colour begins to look drained, bleached, and yellowed, it's an indication that something is amiss. That something is usually a particular nutrient, without which the plant begins a struggle for survival.

With the recent heavy rain showers many plants have begun to exhibit yellowing of their leaves, as all that water from the sky washed precious nutrients down and away from their roots. The two main elements that you may find your garden plants lacking in are Nitrogen and Iron, so lets have a look at their symptoms, causes, and solutions, if they should be found wanting in your garden.

Nitrogen Deficiency
Deficiency symptoms: Pale green or yellow leaves.
Although more pronounced on older leaves, this shows up as a uniform yellowing of leaves including leaf veins. On occasion this is combined with the leaf petiole developing a reddish-purple colour, the petiole is the small stalk attaching the leaf blade to the plant stem.

Cause: Your soil has insufficient levels of the nutrient Nitrogen (N) to allow normal plant growth. This may be because your soil is too low in organic matter, and/or it drains much too quickly (sandy soil) leading to nutrients being washed away.

End result if left unresolved: Sickly looking spindly plants with decreased leaf and shoot growth. Such weakened plants are prone to attack from every bacteria, fungus, virus and pest going.

Solution: For an almost instant pick-me-up apply a nitrogen rich liquid feed to the root-zone and foliage of your affected plants. Follow this with an application of a slow release fertiliser to the base of the plant i.e. well-rotted farmyard manure (best), fish blood and bone, or pelleted poultry manure.

Iron Deficiency.
Deficiency symptoms: Pale green or yellow leaves, with leaf veins remaining conspicuously green, most obvious on younger leaves. The yellowing spreads over the whole leaf until it becomes almost completely bleached white.

Cause: Your plant requires the nutrient Iron (Fe), without it a chlorosis of the leaves begins. This deficiency may be because your soil is too low in organic matter, or if your organic matter levels are in fact adequate, it may be because your plant cannot extract the nutrient. You see Iron has low mobility in compacted and high pH soils (alkaline/limey).

End result if left unresolved: Leaf fall, shoot dieback, and unsatisfying flower and fruit production.

Solution: For a quick fix apply a liquid feed designed for use on acid-loving/lime-hating plants to the root-zone and foliage of your affected plants. Look for liquid feeds labelled Sequestrene or chelated iron. Another way to also decrease your ph, or make your soil more acid is by applying sulphate of iron to the soil around the plants at a rate of 100g per metre squared for each drop in ph point.

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Follow this with an application of well-rotted compost/farmyard manure to the base of the plant to up the fertility and acid levels. As well as compost/farmyard manure there are also many organic materials you can recycle by digging in around your plants and help acidify the soil. Used tea leaves/teabags, pine needles, and shredded/composted leaves are just a few handy ones that come to mind.

Of course you could discover that you have planted a total lime-hating plant into your lime-laden garden. If that's the case you may be fighting a loosing battle, so just accept defeat and opt to grow that particular plant in pot filled with ericaceous (acid) compost. To help you avoid planting lime-haters into alkaline soil here is a short list of those lime-hating plants.

Lime-hating Perennials.
Gentiana (Gentian)
Lithodora diffusa 'Heavenly Blue'
Celmisia (New Zealand daisy)
Dodecatheon (Shooting star)
Shortia (Oconee bells)
Meconopsis (Tibetan poppy)
Primula denticulate (Drumstick primula)

Lime-hating Shrubs.
Azalea
Calluna (Heather)
Daboecia (St. Dabeoc's heath)
Erica cinera (Bell heather)
Camellia (Japanese Camellia)
Clethra (Sweet pepper bush)
Desfontainia (Spiny desfontainia)
Enkianthus
Pieris
Rhododendron
Pernettya/Gaultheria
Magnolia
Kalmia (Mountain laurel)
Fothergilla (Mountain witch alder)
Leucothoe (Dog hobble)
Hamamelis (Witch hazel)

Lime-hating Trees
Eucryphia
Embothrium (Chilean fire tree)
Nothofagus (False beech)
Sassafras
Oxydendrum (Sorrel Tree)
Stewartia (Deciduous camellia)
Nyssa (Black tupelo)
Liquidambar (Sweet gum)

Lime-hating Fruit plants
Vaccinium (Blueberry/Cranberry)

Any queries or comments on Yellow leaves on plants, causes and cures, please post below.

[artalis]

Hi James,

The cordylines that I bought locally were spotted yellow on all the leaves on purchase and I was told that in time they'd settle down, no need to apply any fertiliser etc.

The upright ( indivisa ) grew out of it, but the other ( australis ) has never outgrown the yellow spotting on all the leaves.

Is it nitrogen or iron deficiency?

thanx

artalis

[michael brenock]

the rhododendron in picture I think is suffering from Manganese deficiency rather than iron Deficiency. The iron deficiency would show as white or bleached leaves at the growing point, Magnesium deficiency shows up in the lower leaves mostly or solely. Manganese deficiency can be corrected by the addition of a solution of Potassium Permanganate (Condy's Crystals). Iron deficiency is corrected by adding a dilute solution of Sulphate of Iron (too much can kill). shortage of Nitrogen can be easily corrected by the addition of fertilizer containing Nitrogen (Calcium Ammonium Nitrate), acid soil prevents the uptake of manganese.
michael brenock horticultural advisor (retired)

[michael brenock]

a correction to the previous contribution manganese availability is prevented by High pH (the opposite to what I stated) so check your soil pH as your soil may have too much lime present, Homer nods.
michael brenock horticultural advisor (retired)

[James Kilkelly]

[artalis]

Hi James,
Thanks for your reply. Here are a couple of pics. taken with the handy mobile phone...even if the leaves were shaking in the breeze I hope you can distinguish the uniform spotting all over the leaves.

artalis

[artalis]

So now I am getting pushy apologies in advance James,

But, if you can, could you take a look at this pic. please of a dwarf apple tree from the Coronet group, named Elstar/Falstaff......it has no dev. apples or signs of faded blossom. Was advised on the forum here, ( under the trees thread) that if it is a vigorous grower to leave it unpruned, come Autumn. The new growth appears to be about 10 inches long. What do u think, is it vigorous?

artalis

[michael brenock]

looks like a vigorous tree to me with so much growth. at this stage i suggest that you pinch out the top end of the shoot, remove about 2 inches (5cms) and hope that fruit buds or spurs develop at base for a crop next year. make sure that the budded part of the stem is above soil level (the result of planting too deep) and that scion rooting has not occurred.
michael brenock horticultural advisor (retired)

[michael brenock]

the Cordyline spots look like Rust (Puccinia) to me but not serious enough to warrant control measures unless the younger leaves are attacked. while the picture shows a very good close-up view it does not give any idea as to whether the disease is all over the plant or at one side or spreading from old to the young foliage. if it is the latter then cut off as much as possible of the older leaves and burn them.
If this is weather related, only occurring when temperatures and humidity are high then let it alone and the weather will change sufficiently to halt the disease's progress.
michael brenock horticultural advisor (retired)

[artalis]

Thanks for that Michael.

You could well be right about it being a rust. However the underside of the leaves are yellow and not brown as specified (RHS def. ) for the identification of rust. The upper side as seen in the photo has yellow spotting all over it, but the surface of the leaf is flat with no raised spores or postules etc. The yellow spotting appears translucent when looking up through the tree canopy towards the light.

Have been wondering about it for 3yrs, that's when I bought the cordylines. I have been removing old, yellow spotted and damaged leaves from year to year, hoping to encourage new growth. Almost all of the mature leaves are affected by the spotting. New growth is unaffected, but may gradually succumb to the yellow spotting if I remember correctly. Looked in my RHS encyclopedia and there is a fungicide treatment available for rust - penconazole or myciobutanil.

If it does no harm I may give it some fungicidal treatment later. I wonder when would be the best time of year for this?

Otherwise the cordyline blossoms regularly and looks strong. I won't remove too much of the foliage as it will need some winter protection.

Thanks again for your useful information and help.

artalis

[artalis]

[artalis]

[James Kilkelly]

As I thought , the ould orangey yellow spots..... like as if someone flicked a paint brush at them.
My inkling was rust just as Michael has posted.
Remove affected leaves and improve air circulation would be my first tips.

[artalis]

Thanks for the diagnosis Michael and James-so it's a rust and not some mineral deficiency .

If I remove all affected leaves there will only be a dozen or so new ones left, in the centre, and I think that would expose the tree to frost damage come winter.

I might have to compromise on this one between removing some leaves along with using a fungicide treatment?

Any other thoughts guys, regarding the risk of frost exposure in winter, if most of the existing leaves are removed now?

thanks,
artalis

[artalis]

Thanks Michael,

I pruned the top 2 inches of the new growth on the Coronet Elstar/James Grieve this morning thanks, so will let you know what happens. I see some pink bud tips beginning to form now on some branches. Wondering if that is the beginning of spurs or just more new leaves?

Also got an email from the owner of the Coronet group Dr. Pat McD, who advised little or no pruning, except in the Winter (aaagh!) He also commented that it should have apples by now. He also suggested that after light pruning it might produce some apples next year.

Will let you know...
artalis