cold test on seedling New Zealand lemonade

[poncirsguy]

Just brought my Seed grown New Zealand lemonade tree inside So far it has seen 22F, 22F, 20F, 25F, and many hard frosts. to date. I am warming the roots up to hibernation temperatures for that of an in ground tree so I can put it back outside for the up coming 17F, 13F to determine cold hardiness of this cultivar 01-02-2022



It is now down in an unheated basement to prevent coming out of dormancy.  It has seen 2 months with most nights below freezing.

[Jibro]

Interesting experiment... I would like to know too how hardy NZ Lemonade is, I want to use it for crossing with Trifoliate so your data will be usefull for me, thanks.

[poncirsguy]

Going down to 15F tonight.  My NZL is outside in cold out of the bright sun.  When the sun drops behind the hill I will place the tree in and insulated doughnut to hold the roots at freezing while exposing the trunks to very cold air.

[poncirsguy]

Tree is in position and the pot, roots and first 3 inches of trunk are insulate with cold 30F'ish leaves.

Wrong picture

[tedburn]

Hello Poncirusguy,
interesting experiment, I have a poormans orange also called   Newsealand Grapefruit which is called to need lower amounts of summer heat for the fruits than normal grapefruit, but I guess Newzealand lemonade is an other citrus variety  ?

[poncirsguy]

The poorman orange is very different than the New Zealand Lemonade.
http://citruspages.free.fr/sweetoranges.php#hybrids

[poncirsguy]

The tree still looks good and will go outside tonight for the 9F low.  I will remove several high branches to root.  If they truly survived 15F I will know in 2 weeks.  If the tree dies tomorrow morning but survived the 15F we will all know the limitations of full hardened NZL

Very little visible damage.  A few leaves' stem collapsed.

[Millet]

Poncirusguy, I will be looking for your results

[poncirsguy]

I have Planted the cuttings that have been tested to 15F.  The temperature dropped to 11F and the tree in inside for good to get final results.  The lower trunk was insulated so I can graft a mature NZL mud to the roots for a own cultivar roots NZL tree of fruiting age and still small.



just brought inside from 11F


3 hours later.

[poncirsguy]

Things look good for 16F for the NZL.  As for 11F,  Most leaves are badly contorted but when crushed they smell nice and lemony.  No bark splitting.  The smallest twigs show some desiccation.  a few of the lower leaves look fine.

[hardyvermont]

Have you been bringing the plant back indoors after every exposure to cold?

[poncirsguy]

I brought the tree in after the 16F and placed in in a dark cold unheated room so I would not see 2 day highs of 25. and get damage before the 10F test.  My goal was to see how cold this plant could go in a single cold snap if it was planted on its zone boundary.  I live 2.5 Zones cooler than this trees limits and testing for constant day after day in the high teens and 20's would kill it anyway.  Sometime I miss a tree and it gets hit by a severe cold snap.  This one would survive the 16F and Maybe the 11F.

[poncirsguy]

All leaves on the tree are crisp and dead.  It doesn't mean the tree is dead.  I'll put the tree down in my unheated basement and bring it out this spring.

I found a US897 rootstock tree outside that has endured all the cold and it looks good.

[tedburn]

interesting experiment, but did you insulate the pot by testing ? Because a plant in earth ( with better insulated roots than in a pot) will take more cold temperature I assume. Regards Frank

[poncirsguy]

Yes.  The tree was place in another pot and insulate with 6 inches all around an 6 inches on top of the root collar.  Not quit inground but close.  When I brought the tree back inside the soil was not frozen anywhere. 

[tedburn]

Thank you, so its good ti know what the plant would support if in ground - thank you

[poncirsguy]

The upper most shoots were fully exposed to 16F and might have been slightly covered at 11F.  The stem up to 1/2 inch above the picture is green with a very distinct line of brown above that point and it was down to 11F.  My conclusion is 16F is the minimum safety survival temperature an it should be grafted to FD or Pt.