Return to the Hosta Forum | Post a Follow-Up

Heat Dormancy?

Posted by moccasinlanding z9A AL (My Page) on
Mon, May 14, 12 at 23:32

I looked for this term, because somewhere I read that hosta can go heat dormant. I found only one place which mentions it, and it was the HL Don_R lists. The one specifically called Sun Tolerant Hosta.

"In areas where summers are very hot and dry, hostas should be planted in some shade, as the sun is just too intense. In these environments, hostas may go heat dormant for the hottest part of the year."

And that is where I am focused at this time. Where can I go to find more about the issues of heat dormancy for a normal hosta gardener who is not a pro? Me.

If they go heat dormant, say sometime around August dog days, is that the end for this year? Or will they emerge again as the weather cools in mid October, do their root growth in a big rush, and then assume it is winter along about January?

Last year, the nearly 20 hosta I had from Massachusetts underwent some dormancy in November before we hauled them to Alabama. This year, they will have to adjust to a different sort of seasonal cycle. I'm afraid to think how confused they might become--as well as myself.

Has anyone in the higher zone numbers encountered ANY heat dormancy? From a thread which BKay commented in, she indicated that her hosta in zone 8a basically observed the same cycle as in other parts of the country.

My original 20 hosta from last year are still in pots. The rest of my plants were purchased this year, now totalling upwards of 137. The three in the ground did not come up as early as those in containers. I'm watching to see if they also grow longer, or bloom and give up.

Anyway, point me in the right direction to read more about heat dormancy. Which must not be the same thing as death or winter dormancy...... should I do something to keep it from happening if at all possible? Is it a bad thing, or will the heat dormancy save their little green lives?

Follow-Up Postings:

RE: Heat Dormancy?

its a reaction to stresses .. heat and lack of water ...

usually happens in prolonged drought in summer... july/august

its also known as summer dormancy ...

they do reflush.. but i think the plant is set back.. due to the energy to reflush.. instead of storing energy in late summer in new root growth for next year ...

i think if kept properly watered.. it will be avoided ... but then.. i never tried such in z9 ...

dont forget.. hosta transpire.. or sweat ... so the suggestion to insure shade.. in the afternoon.. in the heat of the day ... plus the added water ... should alleviate the stress ...

now that i think about it.. is also happens.. during the season. where night temps.. do not give a transpiring plant .. time to recover.. before the next days onslaught of heat ...

there MIGHT be a FAQ on such ...


RE: Heat Dormancy?

I had a few that went dormant last year right after the heatwave broke. It wasn't from lack of water since I was watering every other day and it wasn't from direct sunlight as they were under a 60% shade cloth under the Maples. I thought it was strange being that they all looked fine through the high heat. Not a single crispy leaf. I just attributed it to stress from the weather. A couple of things came back smaller this year which is unusual for me. I blame it on the screwed up weather.

RE: Heat Dormancy?

but frank.. how hot was it at night..

the roots can only pump so much water.. no matter how much you try to drown it..

but if it sweats more during the day.. than it can recover at night.. the net affect is downwards ...

i dont know the answer.. i am debating alternatives...

when this happens.. by the time 'see' the leaves brown or yellow.. the plant is already dormant ... its too late at that point .... just keep watering.. and see what happens ....



I think it was staying in the 80's at night. Not sure though. I was struggling to get through it. I almost went dormant.

RE: Heat Dormancy?

I'm thinking that the night temps might be the real kicker.
If it were not for the dang blasted foliar nematode problem then I'd say a misting system to keep the nights cooler would work, with a fan blowing cooler air across them. I'm up to try anything to keep them healthy.

Right now, DH is digging holes for the shade structure poles, and just as I expected, besides tree roots, there is a lot of clay about a foot down. So building the area up with a foundation of pine bark over newspaper, and anything else that I can get to make it drain nicely, won't that help keep the roots cooler?

I have 90% shadecloth about 6 feet wide, two strips of it attached loosely in the mid seam so hot air can rise and exit. Hopefully this will also reduce the amount of rain splashing on the leaves below.

I'll look for the FAQ, Ken, but I did a search for hosta heat dormancy and found no hits. Just the mention of it in Don's sun tolerant hosta list. However, I also seem to remember vaguely a mention of high night temps being an issue for some reason.

Well, maybe I could air condition them at night. But even God doesn't seem able to moderate the heat here in south AL! Makes me think about living inside a hemisphere bubble.

Housecleaning day, gotta run. The vacuum, that is.

RE: Heat Dormancy?

In the summer, our night temps are usually in the '80's. Mobile's probably no hotter than we are, just more humid. If by heat dormancy, you mean die back to the ground, then, no mine don't do that. They usually don't grow anymore after June. Then, in July, they start looking tacky. They stay pretty much like the photos until the days start to get short. (They begin to get burned edges, too.) Then they turn slowly yellow until frost gets them.


old blue leaf 910


RE: Heat Dormancy?

The only hosta I have that comes close to heat dormancy is Moonlight Sonata. I used to think I would never see it again, but it always comes back big and lush in the spring.

RE: Heat Dormancy?

BKay, is that sun scald on your leaves?

Like V near the pointy end of many leaves.
Sweating does it?
I'll have to watch out for heat dormancy, because we had 91 today, and probably 100% humidity. I was soaking wet after taking photos of all the hosta today--and that doesn't require a lot of effort.

However, tonight's temp is now down to 67--which is really great.

RE: Heat Dormancy?

No, they are in full shade. Maybe you could call it a little dappled shade during the day. That's just how they react to the heat.


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Hosta Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here