Cupping leaves--too wet or too dry?

marc5(6aOH)May 25, 2013

I'm hoping you all can help me determine what is causing my pawpaw leaves to cup up and curl. Please see photos. Is it too wet or too dry? I was trying to use moderate watering. I am experimenting with several mixes. Note that one is a 1:1 peat:sand mix, the other is in 5:1:1. The worst tree is in the peat sand mix, and perhaps that is telling us something. A third mix used is 9:1 pine bark:compost, and those trees, while some are cupping, look the best. Again, another clue? While my first reaction to the leaves is that they look dry, perhaps because the faster drying mixes look better, is there too much moisture?

I am using dowels to help me with moisture levels, and the bottom half of the containers seem plenty moist. The containers are Rootmaker, and the mixes contain Osmocote at a rate of 12 lb/cubic yard--about 2 tabs/gallon. Small amounts of micronutrients are also in the mix. Some acid is being injected into the water. Newly-germinated pawpaws in 5:1:1 in Rootmaker 18s look great. Thank you for any ideas.

Marc

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tapla (mid-MI z5b-6a)

Either Ca or Mg deficiencies often cause deformities in the shape of cupping (did you add dolomite to your mixes? does your fertilizer contain Ca/Mg?). Deficiencies of zinc and molybdenum can also cause the same distortions. Too much or not enough water can do it, too.

Any chance the plants caught any herbicide over spray? What Osmocote formulation did you use? Selecting a product that matches your zone and plant requirements can have a considerable impact on what benefits are gained by your plants.

Al

    Bookmark   May 27, 2013 at 12:31PM
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marc5(6aOH)

Al, thank you for your response. You are the foundation of this forum. I did not add dolomite to the mixes, as my water has plenty of Ca (78 mg/L) and Mg (30 mg/L). To the mix I added Florikan MIV Meg-Iron, which has .09% Zn and .06% Mo. I added 1 lb./ cu. yd, or about 1/6 tab per gallon of mix. The Osmocote in the mix was Classic 18-6-12 (I know you like this ratio) in 8-9 months. There is little chance of herbicide spray, as the plants are in a high tunnel. Could it be too much or too little water? The problem with plants seems to be that too much or too little water can result in similar symptoms.

Unless I come up with a definitive answer, I am hoping an experiment will shed some light. I am placing two similar plants side by side. For one I am cutting back on water. For the other I will increase the watering amount slightly. We will see which looks better over time. I hope they both do not die!

Thank you again,
Marc

    Bookmark   May 27, 2013 at 10:53PM
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