Eucalyptus Cinerea (Zone 6a Colorado)

[COpalms]

I have a Eucalyptus Cinerea (AKA Silver Dollar or Argyle Apple) planted here in zone 6a Colorado. It is hardy down to about 10f (-12c) or zones 8a-11. I have one planted in a rock area in the cul-de-sac of my yard, where it's at least shielded from all four winds and faces south-west. I gave it 3-5 inches of mulch, and it was covered in snow, but it underwent a 6-8°F night (-12c) and had no damage whatsoever. It looks beautiful with the blue leaves and the purple-ish leaf tips. Not quite sure what to expect, but hopefully it survives. I may put a frost cloth over it, but apparently, they can survive zone 6a with dieback. I've heard multiple things from different sources, so I'm not sure what to expect. Any advice, ideas? Do you have any experience or wisdom to share with me in Eucalyptus cinerea or eucalyptus in general? Have a great day, God bless! (If you want any photos, just ask and I'll attach them)

[ChrisA]

That’s a good experimental eucalyptus since they are easily acquired.  I remember there was one growing in Albuquerque several years back that eventually got to about 15-20’ tall but eventually was frozen to the ground. It attempted to grow back several times but dies after a few years of struggle. It was in planted in a median and never received protection. Not sure it ever was on a water system either which may have affected its ability to recover from consistent freezes.

I tried Coolibah (Malaleuca microtheca) a few times starting in the late 90’s. We had two mild winters and it lost most of the leaves and thin twigs in those milder winters but then got cut to the main trunk, afterwards it died yearly to the ground, never to recover. The nursery trade states it is hardy to 5F but don’t believe that for a second. I would say below 18-20F you will see leaf damage and below 15F very serious damage will take place. Below 10F it’ll die to the ground.

Be aware that Eucalyptus does not show freeze damage until temperatures have warmed back up.  Hopefully your Argyle Apple will recover. If you can keep the base from freezing yours may sprout back from the bottom once summer temps return.

Good luck! And share some photos, we all love photos here!

[Jonathan]

19 hours ago, ChrisA said:

That’s a good experimental eucalyptus since they are easily acquired.  I remember there was one growing in Albuquerque several years back that eventually got to about 15-20’ tall but eventually was frozen to the ground. It attempted to grow back several times but dies after a few years of struggle. It was in planted in a median and never received protection. Not sure it ever was on a water system either which may have affected its ability to recover from consistent freezes.

I tried Coolibah (Malaleuca microtheca) a few times starting in the late 90’s. We had two mild winters and it lost most of the leaves and thin twigs in those milder winters but then got cut to the main trunk, afterwards it died yearly to the ground, never to recover. The nursery trade states it is hardy to 5F but don’t believe that for a second. I would say below 18-20F you will see leaf damage and below 15F very serious damage will take place. Below 10F it’ll die to the ground.

Be aware that Eucalyptus does not show freeze damage until temperatures have warmed back up.  Hopefully your Argyle Apple will recover. If you can keep the base from freezing yours may sprout back from the bottom once summer temps return.

Good luck! And share some photos, we all love photos here!

Hi Chris, I'm guessing you meant Eucalyptus microtheca? If so, not surprising it died...that species is native to tropical savannah in northern Australia, would be very surprised if it could tolerate temps much below freezing. You might have more luck with the other Coolabah species, Eucalyptus coolabah, which reaches much further south and inland, including some pretty frosty winter areas. I've got one doing pretty well down here in Tasmania. It's a lovely tree as well!

[ChrisA]

 Hi Jonathan! Thank you for the reply.  Yes that is correct, I should’ve written Eucalyptus microtheca.  I’m not sure the provenance of those commercially sold in the US, especially in southern Arizona. I hadn’t heard of E. coolibah but will have to check that out.  I wish we had more options when it comes to these beautiful trees!  How hardy would you say coolibah species is to cold temps?  Are eucalyptus difficult to grow from seed? I’ll have to find some photos that I took so I can hopefully get input from those of you down in Australia and New Zealand who have much more knowlegde on these. Thanks again!

[SeanK]

About 20 years back there was a E.cinerea near me. After a couple of +single digits winters, it disappeared.

https://plants.ces.ncsu.edu/plants/eucalyptus-cinerea/

[Jonathan]

18 hours ago, ChrisA said:

 Hi Jonathan! Thank you for the reply.  Yes that is correct, I should’ve written Eucalyptus microtheca.  I’m not sure the provenance of those commercially sold in the US, especially in southern Arizona. I hadn’t heard of E. coolibah but will have to check that out.  I wish we had more options when it comes to these beautiful trees!  How hardy would you say coolibah species is to cold temps?  Are eucalyptus difficult to grow from seed? I’ll have to find some photos that I took so I can hopefully get input from those of you down in Australia and New Zealand who have much more knowlegde on these. Thanks again!

Hi Chris, Eucs are generally very easy to grow from seed, just surface sow them on a reasonably well drained propagation mix and water them in. The seeds are tiny and need exposure to light to germinate, so don't cover them over at all. I've found mixing a bit of wood ash into the mix helps, as most species regenerate naturally after wild fires and chemical compounds in ash triggers germination. Seed for most species should be reasonably easily available from suppliers in Australia, not sure what your import restrictions are like though?

I couldn't tell you what the absolute cold limit for E coolibah would be but I'd think -5c, so 23f would be reasonable to assume. We bottom out at about-1c, 30f, so not much of a challenge for them here.

[tarnado]

Dessicating, dry cold is the most damaging to all cold-hardy eucalyptus. If you want Eucalypts around, I recommend planting a few each year. The cold winters you have will kill them all, to the ground at least, almost certainly. Still! Keep going for it!