Leaves slowly willting

[poncirsguy]

I have a New Zealand lemonade tree on C35 and a Valentine Pomelo on US897. The US897 started wilting first so I picked its fruit and about a month later the NZL started wilting. I started picking its fruit over the last month. Now 6 weeks into the wilting.  None of the fruits or flowers froze so the lowest temperature my have dipped a  little below freezing.  Any ideas of cause and is this tree a goner

[kumin]

The loose bark appears indicative of a moist cambium layer. Is there a chance the bark surfaces were perpendicular to the sun's rays? If the inner bark was moist and active it may have been vulnerable to freeze damage at temperatures harmless to more dormant branches.

Are the damaged areas facing the sun?

[Millet]

The tree is protected by the 4 layers of glass, but what is the temperature of the soil at the roots?

[poncirsguy]

The soil is cold probably near or possibly bellow 55F.  The sun is not hot on the trees because of the 4 layers of dirty glass.  They get mostly diffused light.  They seem to put on very slow growth and/or flowers all winter.

[brian]

Two of my container citrus (kumquat hybrids) wilted rather suddenly like this, and I still have no idea why.  Roots look fine, soil is free-draining, they are in the same greenhouse with a hundred other (mostly citrus) plants that are perfectly healthy.  But on these, the leaves wilted up and the branches are now dying. 

I would check root temperature for sure, though.  The soil might be much colder than 55F, and possibly going long periods below this temp so roots may become inactive.

[poncirsguy]

I tried this winter to keep them dormant by not heating the greenhouse unless the temperature inside would drop below 32F.  I did not need to heat until January to keep fruit from freezing.  The trees started wilting Mid January and bark split on one tree.  I have no way of heating the soil so I don't want to heat the air either.  With 4 layers of dirty glass on a warmish sunny day the greenhouse doesn't get hot and at night it doesn't loose heat badly either.  These trees will either come out Ok this spring or they will die.  The other greenhouse has a seed grown fruiting Fukushu and fruiting Meiwa kumquat trees that look really good.  It gets less heat that the lemon and valentine do.

[sea4]

Two of my container citrus (kumquat hybrids) wilted rather suddenly like this, and I still have no idea why.  Roots look fine, soil is free-draining, they are in the same greenhouse with a hundred other (mostly citrus) plants that are perfectly healthy.  But on these, the leaves wilted up and the branches are now dying. 

I would check root temperature for sure, though.  The soil might be much colder than 55F, and possibly going long periods below this temp so roots may become inactive.

Yup, same here. I have more quats than other citrus, but I've had this sudden wilting thing happen a few times on the quats. I have yet to pull a plant out to look at the roots, I rather doubt it would actually tell much.
Very baffling.

[poncirsguy]

The tree in the white circle is an in ground Seville sour seedling I planted next to the C35 to be used as a rootstock transplant.  It has some leaf wilting and destruction.  The Seville sour in the black circle is in a 5 gallon bucket.  If the NCL dies and the Valentine Pomelo lives I will graft a new NZL to the Seville sour.  If the Valentine pomelo dies too.  The greenhouse will be disassemble and the Seville seedling will be grafted and containerized.  Citrus trees do not belong out side in ground in Cincinnati, Oh.  If the NZL survives and the pomelo dies I will plant another NZL.

[Millet]

The more I read about this, the more I believe the soil has become too cold for the roots.  You could purchase an electrical heating cable and circle it at various depths in you greenhouse structure, starting at 2 feet deep and up.  I have an electric heating cable that is 100 feet long.

[kumin]

A 4' deep trench around the perimeter of the enclosure with 2" - 4" thick rigid foam insulation backfilled with soil,serving as a thermal barrier will decrease the bridging effect that channels the warmth from the inside soil to the cold exterior soil. The inside soil can then function as a passive heat sink. In the past I've built several solar greenhouses and these principles are quite effective.

[hardyvermont]

On a sunny day, what is the temperature inside?
Finding that out could eliminate some possible causes to the wilting.

[poncirsguy]

I am thinking that the roots are to cold and the tops desiccated.  The stems are still Ok.  It has only been 3 weeks since the ground hog saw its shadow and 6 weeks is when most stuff comes out, mid March.  I thought about pushing warm air 2 feet deep to warm the soil to 60F and let the soil heat the greenhouse.  My 2 seed grown kumquat trees are doing fine in the other greenhouse.  The greenhouse perimeter has up to 2 feet of leaves for insulation now.

[BorisR]

@poncirsguy, have you bandaged the cracks on the thick branches with duct tape, didn't you?

I have heard that the bark under shelter can crack from high humidity, but I do not know if this is true.

*
OFTOP: If I use "@" in front of the user's nickname, does he receive a notification that he has been contacted? Or does it not affect anything on this forum?

[Citradia]

I’ve seen a lot of my cold hardy citrus die when the bark at the base splits like this. It splits on the south side of the tree in spring after temps have risen enough to cause sap to flow and break dormancy, followed by a freeze that splits the bark. The trees need to stay cold and dormant as long as possible throughout fall, winter, spring. Some blooming and growing in winter even in the greenhouse is a problem since temperatures will drop below freezing in the greenhouse even with supplemental heating when outside temperatures get cold enough. Signs of new growth in March is a bad sign here.

[kumin]

White overwintering poly can be helpful to reduce solar gain. Increased air volume in an enclosure slows the rapid yo-yo effect of alternating clear, cold nights and bright, sunny days.

[Millet]

BorisR  "@" does nothing

[poncirsguy]

More drying of leave and stem die back

Lower level of green is from seedling Seville.