Hardiness of selected Hawaiian trees

[TNAndy]

I have four Koa saplings, a tiny Kukui tree, a whole bunch of Coffee sprouts, a Macadamia bonsai, and some Manila palm seedlings. Our weather, over here on the mainland, is definitely changing with the seasons. Only two and a half weeks ago the overnight low dropped below 60 degrees F for the first time. Earlier this week, it dropped below 50 degrees for the first time, but has now reached a night time low of 45. I have found the following info and am wondering if anyone has any direct experience that confirms the internet claims.

Acacia koa (Koa) can tolerate a light frost, correct? Can it handle a freeze? How cold and how long?
Reference: http://www.na.fs.fed.us/pubs/silvics_manual/Volume_2/acacia/koa.htm
Here's a conflicting opinion: http://davesgarden.com/guides/pf/go/66293/

Aleurites moluccana (Kukui) can tolerate a light freeze, 25 degrees F (USDA zone 9b), right?
Reference: http://www.desert-tropicals.com/Plants/Euphorbiaceae/Aleurites_moluccana.html

Coffee species are damaged by light frost. How does the Kona variety fare in the cold? (I know it snows--occasionally--on top of some of those volcanoes!)
Reference: http://www.encyclopedia.com/doc/1S1-9199407110633364.html

Macadamia species can be outright killed by light frost, especially when young. They grow a bit more frost tolerant as they mature.
Reference: http://www.crfg.org/pubs/ff/macadamia.html

Manila palms can handle a heavy frost, 30 deg. F (USDA zone 10).
Reference: http://davesgarden.com/guides/pf/go/2223/

I brought my Clove, Nutmeg, Cinnamon, and Surinam Cherry inside two weeks ago.

[Allen]

Andy,
I would rank your plants in order of cold hardiness, Koa, Coffee, Kukui, Manilla palm, and Macadamia. Doubt any will survive hard freezes you have in your area. Koa and coffee do pretty well in Hawaii where temps drop to 40 and occasionally lower. The others not so much.

Otherwise they should live, but not flourish with lower temps. Temps you mention will effect these plants more severely as you move down the list.

Let me know if that helps.

[Allen]

Andy
Temps for Koa


mean minimum temps 36 - 61
mean annual temps 48 - 70


Much more here:
http://www.agroforestry.net/tti/Acacia-koa.pdf

[TNAndy]

Thanks for the confirmation and advice. I especially appreciate your advice on the Macadamia; the references on the internet made it sound more hardy. Of the plants listed above, all but the Koas are inside, now. The low temps are still in the mid 40's F, so I have a couple more weeks to make room for the remainder.

Oh, yes, I know none of these plants will survive a hard freeze. That's why I have them in containers--the big ones on casters! I don't plant much of anything in the ground.

[Allen]

The last three, kukui, manila palm, and macadamia will show similar slow growth in cold climates. But here on the Big Island, it is quite easy to see macadamia decline in growth as you go from sea level to 2000ft. Kukui and manila palm seem to rebound when warmer months come back, macadamia not so much.

[TNAndy]

Regarding cold hardiness, my potted Macadamia survived where my Manilla Palms did not. The Macadamia was/is by no means happy; numerous leaves remain bleached white from last year's cold. We'll see if it makes it this winter.

Young Coffee trees wilt at near freezing temperatures. They recover, slowly, when they warm up. Koa trees do not like being brought indoors, period. Subsequent cold doesn't make them any happier. Outdoors, I know of one planted in a very protected spot in USDA zone 9. I will post if it lives through this winter.

I also know of a Kukui (Candlenut) and Plumeria planted in this same protected spot. With no extra help, the Plumeria has lost all leaves. The Kukui is growing with the Koa under a sheet.

Betel Palms also die with relatively little exposure to cold. Coconut Palms expire if their roots drop below 50 degrees F, although the trunk can stand brief exposure to lower temps.

My Chusan Fan Palms, Pindo Palms, Pygmy Date Palms, and Cat Palm seem to be doing just fine.

Cocoa trees will not survive below about 40 degrees F. You don't figure out they are dead until several days later. (Grrrrrrr!!!) I wouldn't be surprised if it's the roots that die, because the tree wilts, then shrivels. The leaves remain green for quite a while just to fool you.

Pepper vines (Piper nigrum) lose their leaves and young shoots at these temperatures. I hope mine make it through the winter. Betel Pepper vines are somewhat hardier, although the first freeze kills them. Given fertile potting mix, Betel Pepper vines will overflow their container.

Blue Ginger (not a zingiber relative) dies back when exposed to freezing temps. Most lower leaves and stems look OK. Flowering Gingers are fine. Cardamom is fine. My True Ginger is turning yellow, but I'm sure the rhizome will resprout with higher temperatures. If properly mulched, Flowering Gingers will resprout in USDA zone 7.

Mature True Cinnamon leaves shrug off the cold, but leaves from recent flushes get progressively damaged as temperatures drop. Leaf veins and young stems tend to blacken and die.

[TNAndy]

Ugh. I couldn't have been more wrong about my coffee plants. It now seems wilt means death, same as with cocoa saplings. They won't recover. They merely take even longer to die than cocoa. The sunroom heater incident was far more catastrophic than I thought.

Interestingly, a handful of coffee saplings were able to shrug off the cold. They lived--surrounded by other plants that didn't. Maybe a few percent of coffee seedlings are ever-so-slightly cold hardy?

[TNAndy]

The Koa and Kukui trees planted in USDA climate zone 9 reportedly survived the winter. From what I hear, 2010-11 was a record cold winter for the Florida panhandle. During the coldest nights, the two small trees were covered with umbrellas and sheets. I'll give a more detailed report when I see them in person. While Koa certainly doesn't like freezing cold, you do far more damage simply by bringing it indoors than anything else.

I still have a very few coffee trees that survived the heater incident freeze. One seems perfectly OK. It never showed any sign of damage. Its older leaves remain a dark, healthy green. Now it's growing new, bright green leaves. A couple of the runts yet live, but they were segregated and didn't suffer quite the same cold as the others. Their leaves are dark green and growing, too, albeit slowly (no faster than before, anyway--that's why they're runts). A few other coffee plants appear alive, but I haven't seen any new growth whatsoever and the leaves have a yellowish tinge. I've seen those symptoms before and unfortunately, the prognosis is not at all good. Just like with coconuts, I suspect it's the roots that can't stand the cold.

My Macadamia's leaves seemed to be more heavily damaged by the 2009-10 winter than the 2010-11 winter. I'm beginning to think something besides cold caused it because it was quick to recover from the heater incident. In fact, it is really shooting up this year.

My Chusan Palms ignored the cold where a couple of Pygmy Date Palms were damaged and one died. I started a crop of Pindo (Jelly) Palms. They are very young. I can't see any cold damage, but at this early stage, infant mortality is a bigger concern. All of these palms are supposed to tolerate light freezes.

I would rank the plants this way (least hardy to cold tolerant): Nutmeg, Clove, Coconut, (must stay warm--60+ deg.F) Betel Palm, Cocoa, Manila Palm, (cannot tolerate cold below 35 deg.F) Coffee, Vanilla Orchid (all killed at 32 deg.F), Black Pepper, Plumeria, Betel Pepper, Pygmy Date Palm, Macadamia, Koa, Kukui, (killed by hard freezes--below 30 deg.F), Allspice, Cinnamon, (leaf damage from frost, but plant recovers) Citrus, Pindo Palm, Chusan Palm, Tea (freeze tolerant--20+ deg.F).

Please note, these are simply my observations. This information may only be valid in my sunroom where there is no wind and no frost (unless the temperature drops below 32 deg.F). I have not scientifically tested any of these plants. Your mileage may vary.

[TNAndy]

I got a chance to examine the Koa and Kukui trees this week. They are planted in the central Florida panhandle a half mile (give or take) away from the beach.

The Koa suffered less damage from the extra cold winter than the Kukui. I can't tell if the Koa had any damage from the cold, but the formerly 7 foot tall Kukui froze back to about a foot off the ground--basically the part protected by pine straw mulch. Since then the homeowner cut off the dead part. This spring, it has sprouted several new branches. I expect this die-back is what will happen most years.

I read elsewhere that Koa trees, once pot bound, never really recover. I'd say this could be the situation here. While I did not detect any damage I could attribute to freeze-back, this plant is not strong or even particularly healthy. The stems seem thin to me and the leaves only grow at or near the stem tips. If Koa were not a legume, I'd suspect a severe lack of nitrogen (and that could be another problem anyway). But it is certainly no worse for the wear than the Koa I kept in my sunroom in Tennessee.

I wonder how healthy this Koa would now be if I had skipped the container stage entirely by planting it directly in the ground in Florida. I suspect it can withstand temperatures in the 20's F. just fine. If you have a Koa growing in the ground in Florida or anywhere else in the contiguous 48, please post a description here. From what I read, this tree is becoming rare in Hawaii--particularly large specimens . Koa wood is so beautiful, this species MUST be saved!

[TNAndy]

Almost forgot... Plumeria is by no means hardy in the central Florida panhandle no matter how close you are to the beach. If the first frost didn't kill this specimen, the second one did.

[TNAndy]

It took far longer for my True Ginger (Zingiber officinale) to sprout from the roots than I thought. The freeze resulting from the heater incident killed everything but the rhizome, and a large proportion of that as well. It has taken this long for vigorous growth to resume.

Isn't it odd that my flowering Gingers, Kahili and White, suffered no damage or slowing of growth rate due to the freeze?

As I reported earlier, only one of last year's healthy Coffee saplings has thrived where all the others were killed or extremely damaged. This plant's leaves have remained dark green throughout. It has grown by inches this spring and summer. A couple of survivors kept their leaves, but those leaves remain yellow and droopy, and only one plant has grown any new leaves. Several plants that had their tops frozen back have sprouted new growth from their lower trunks. Of course, the vast majority of the Coffee saplings just plain died.