Please help my citrus trees...yellowing leaves

[Meeelia]

Hi all, this is my first post and I'm pretty new to gardening in general. I have a 2 questions about citrus plants that I would be most grateful if people could help with. I have fed both with Osmocote citrus fertiliser a couple of weeks ago and watered with seaweed solution recently.

I have Yuzu plant that's approximately 3 years old. The leaves started off a lovely dark green but over the past year most of the leaves have dropped and the remaining leaves are very yellow with green veins. I've done lots of Googling but find it hard to differentiate between the various deficiencies...could anyone please help? It produced one small fruit last season and although it's now spring here there is no new growth. I cut some of the branches in winter hoping for new growth but nothing has happened so far. Here are pics:

Secondly, my Meyer lemon is also starting to have yellow leaves...I'd really love to rescue it before it goes down the same path as the yuzu! It otherwise looks healthy, lots of new growth and buds are coming out. Here are pics:

Any suggestions or advice would be most appreciated! Thank you!

[imafan26]

How long has it been since it has been repotted. When citrus looks like that it is usually a soil issue. It is easier to repot in good potting soil than to try to fix it.

Soak the pot in a tub of water until the bubbles stop and then drain it about 10 minutes later to make sure the roots get a good drink and the rootball is not dry in the middle.

Miracle Grow potting soil , Black Cow and Gardener and Bloom are good potting soils. Make sure you are using potting soil not garden soil.

Pot up one size bigger. I prefer 4 or 7 gallon egg cans. They are taller than they are wide and the roots will have more space that way.

Check the roots if they look good, then repot and try to keep the rootball intact. I do score my root ball to break up any circling roots.

If there are dead and black roots, I would carefully trim them away but still try to keep most of the rootball intact.

Make sure the lemon is at the same level in the new pot as it was in the old one.

Water the plant in well and keep it in the shade for a few days if it is still hot and then gradually bring it back out into the sun. You can mix up a gallon of water with 1 tablespoon miracle grow plus 1 drop of super thrive and water in the plant. Only use one drop of super thrive. It is a root stimulator and will kill a plant if you use too much. It can only be used on well fed plants and only once a year.

I prefer to plant my citrus in pure black cinder in a twenty inch pot. Black cinder contains no nutrients and does not hold water well so the plant needs to be watered everyday or every other day. The plant will be totally dependent on getting nutrients regularly. The advantages is that I do not have to worry about the soil going sour or the rootball compacting with the water going around the rootball while the roots in the center die of starvation. Cinder has a lot of airspace so there will be a lot of room for the citrus roots. The downside is that the pots are very heavy and need a dolly to move them although I can still tilt them to make sure the tree is not going to ground. My oldest tree is about 19 years old and it has been in the same pot for about 16 years.

[Meeelia]

Thanks for the quick reply Imafan26! I haven't repotted the yuzu at all since I got it bare-rooted about 3 years ago. I'll get a bigger pot and will definitely try your tips.

The lemon was repotted about a year ago with potting mix for citrus so I don't think that's the problem though...

[imafan26]

Citrus are Mediterranean plants. They like well drained soil and in the ground only need a good deep drink once a week. The soil should be slightly acidic. Citrus food contains sulfur as well as micronutrients the plant needs so you should have had enough nutrients if the tree was fed regularly at least every three months or so. The only thing I know of that can cause global yellowing is because the nutrients are not being taken up even if they are in the soil

1. Sour soil- pH out of range. If you have added compost to hold water it can make the pH less than optimum. High pH makes micronutrients like iron, zinc, magneseum, boron, and selenium less available and that will show up as deficiencies in the leaves.
2. The soil has compacted and the rootball is not evenly moist. Some of the roots in the center die and less nutrients get taken up by the plant. Leaves wilt and fall off.
3. The soil has too much water holding capacity. Compost based soil mix. It is fine if you don't have a lot of issues with monsoon rain and you don't water on a schedule but only when needed. Otherwise the soil stays too wet, fungal issues crop up and the roots start to rot. If it happens quickly the plant wilts and dies with soggy soil (phythoptora). If the roots have not gotten as far as rot, but is constantly moist, the air space is lacking an the roots become stressed which will show up as generally poor health on the tree with leaves yellowing and falling. The same thing happens when the tree does not get enough water, the leaves shrink, yellow and fall off. Trees will come back better from lack of water than when they get too much.

The other reason for citrus trees to be stressed is from virus.

Huanglongbin or citrus greening disease. It is a relatively new disease but it was spreading.
http://www.californiacitrusthreat.org/h ... eening.php

Tristeza virus
Tristeza virus is common worldwide. Hawaii has some of the most virulent variants of the disease and most of the trees have it. That is why most citrus trees grown in Hawaii are grafted onto resistant rootstock. The resistant rootstock will still show signs of the disease eventually and the tree will die but it will take about 20 years vs 3-5 years on susceptible citrus stock. One of the symptoms of tristeza is that the tree will actually become very productive and give a lot of fruit for some years and then the bark will start to peel off. Cutting off the dead branches help but if the bark starts to peel off the main trunk, the tree's days are numbered.
http://idtools.org/id/citrus/diseases/f ... e=Tristeza