Sunday, April 20, 2014

Evaluating Winter's Plant Damage

Agave victoria-reginae
 
When you over winter several hundred cacti and other succulents in three wooden boxes, covered by plastic, and heated with small electric heaters, there is bound to be problems.  The potential "big" problem is a loss of electricity during a severe cold period.  Without the heaters, temperatures in the over wintering boxes would drop below freezing in 4 to 6 hours.  There were no power outages this winter and no heater failures.  Most of the plants came through the winter in good conditions, but there were a few sad exceptions.  Perhaps the most notable, and for me the saddest, was my seed grown, 19 year old, Agave Victoria-reginae. 
 
When I first saw it I wasn't sure what had
happened.  This was not low temperature damage.  Why a band of damaged tissue in the center of the leaves?  It took me a day or two to figure out what had happened. 

Notice how the leaves are all in an upright position. This is due to the plant being very dry.  Because the winter was so consistently cold, I had little opportunity to open the over wintering boxes and give the plants any water.  It reacted to the lack of water by pulling its leaves upright to protect the terminal growth and further reduce water loss.  This is a normal reaction.  But what it did is expose the undersides of the leaves to strong, direct sunlight (remember in winter the sun is low in the sky), and basically, sunburn the leaves.  The undersides of the leaves are not normally exposed to direct sun.  They weren't acclimated to direct sun, and when exposed they were damaged.  As far as the plant is concerned, it is fine.  In nature it would continue growing and eventually flower and set seed, its primary function.  But in terms of a nice show plant, it is ruined.  I probably should have anticipated this, but I didn't.  I was concerned with just keeping the plants warm, forgetting about what the extended lack of water might cause.  You live and learn, but this was a tough lesson. 

 


 

6 comments:

  1. Very sad but difficult to anticipate. Each year I have some casualties. Scorch is my biggest problem. Weeks of cloud followed by bright sun can be a shock for the plants.

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    1. Scorch is a serious problem on cacti and some succulents because they can't just shed damaged leaves and quickly grow new ones. Most experienced growers have had problems with scorch but it doesn't seem we pass it down to new growers very well. I looked at a couple general C&S books I have and several had no info on scorch and the ones that did had little information on how to avoid it. I guess it is not as exciting and insect and mite pests or exotic diseases.

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  2. I'm glad it survived, and it is a wonderful visual for talks and lectures about overwintering plants outside of their native environment. I've had scorch issues, too, but in summer, after it's been cloudy-rainy for weeks, then, BOOM, tropical sun. Very hard for plants (and gardeners) to cope with. Thanks for sharing!

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    1. Thanks Marla. You are right, it is a good subject and I am writing an article about it for the Washington, D.C. C&S Society newsletter. I work hard to avoid scorch on the plants I am putting out after winter in the house, but I sure didn't anticipate plants getting scorched because they moved their leaves. But it was my fault, I could have avoided it. Such is part of the ups and downs of growing plants. Hope you are enjoying the beginning of the growing season.

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  3. It is really sad but at least the plant is alive and will outgrow the damage one day :)
    And maybe if you had watered it the damage would be everywhere on the leaves, don't you think? Uppersides, undersides as well as younger leaves in the middle? Please keep us updated on the recovery process!

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    1. Yes, it will outgrow the damage -- in about 10 years! The plant with its leaves at a normal angle was well acclimated to the full sun, it was the fact that the leaves raised up exposing the undersides which were not acclimated. If the plant had been watered a couple times the leaves would have not come up and there would have been no damage. I'm sure there were a couple days during the winter when I could have partially opened the frame and watered the plants. I just thought, they're succulents, they can handle being dry. I bit of laziness on my part and it cost me. I'm not sure I will keep it at this time. Space is at a premium for over wintering and I want to grow more seedlings. I'm sure someone at the Wash DC C&S society (maybe a new young grower), will be willing to take it and nurse it back to show plant status. We'll see.

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