Operation Chill

I have a cherry tree, Starkrimson type.


It’s been in the ground 2 winters.

I bought it locally, so it should be suitable for my area and it should fruit, right?

Not necessarily.

Stone fruit require a certain number of hours (chill hours) which the tree needs to be exposed to temperatures below 7 degrees Celsius (doesn’t have to be ‘below zero’ – interesting). Most fruit are high chill, which require 700 hours plus of chill time.

According to the PlantNet Chill Guide, Sydney is classified as a “medium chill” area. With an average temperature of 12.2 degrees during winter, apparently it gets on average 640 chill hours per season.

In my area during winter, we usually get a few overnight frosts per year. So far this year, at the start of the second month, I’ve observed only 2 days of overnight frosts so far. I’m not sure about the full 640 chill hours estimated – that would be equivalent to just over 2 months of below 7 degree nights, consistently. We’re down one month of a very warm winter already.

I can’t find any info on how many chill hours the Starkrimson cherry tree requires. The only kind that I have found documented to have a “low chill” requirement are Minnie Royal or Royal Lee, available at Daleys – possibly – as a two way graft. These require about 300 chill hours – or one month of below 7 degree C nights.

Thus, Operation Chill:

Operation Chill

What do you think?

Is it the roots that need to get the chill hours – if so, I’m ok.

If it’s the buds and stems, this probably won’t work. I have tried to wedge bigger blocks of ice amongst the branches.

I’ve also read some web posts about people rigging up a reverse green house (cold house?) in order to trick their stone fruit tree. This would only work if the tree did not receive sunshine during winter.

What garden innovations have you rigged up to get around a problem?


4 responses to this post.

  1. […] until much later in September than all the others in the neighbourhood. So there is hope for Operation Chill after all…Hopefully now that I’ve got the bees, I’ll get some cherries this year. […]


  2. […] it the application of ice throughout winter as part of operation chill? After all, with the extra month (210 hours, say; for a total of 360 hours over winter) on […]


  3. I have a 2 year old Anzac peach growing in thick clay. It’s a high chill 600 plus variety and it cropped incredibly well last year.

    It seems to be really a matter of microclimates and year to year temperature variations. What’s written at the back of a planter ticket is useful, but it’s, at best, a generalisation of conditions not a rule. At the end of the day, you won’t know if something grows well and/or produces in a particular spot in your garden, until YOU ACTUALLY GIVE IT A GO!

    Good luck

    Ps: I believe it’s the temperature around the buds that counts


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: