Fern Propagation problem

Browning leaves during hardening of young plants

As I began to remove the humidity domes from the young ferns (Dryopteris erythrosora 'Brilliance'), the edges of the leaves of some of the ferns started turning brown. I consulted with Matt Goeke at the North Carolina Botanical Garden, Brian Aikins at the American Fern Society, Tony Avent at the Plant Delights Nursery and Mart Bumgarner, our local Master Gardener Extension Agent. Several possible issues were suggested including, a hardening transition that was too rapid and foliar nematodes.  

We decided to send a couple of the plants to Mike Munster at the NCSU plant clinic.

Outcome

No pathogens were identified. 

The concentration of salt in the media was very high in both samples submitted. 

I then realized that the water that I was using to water the ferns was coming out of a water softener and presumably removing the humidity domes led to an evaporation of the water and a concentration of the salt from the softener in the media. 

I started using water from our reverse osmosis system and flushed the pots several times. 

Some of the plants survived and started producing healthy fronds. 

The images shown are the same plant before and after flushing with the RO water.

Lesson Learned

Don't water young ferns with water from a water softener.