Hi
That's interesting .I have just the opposite problem
The gingers will crowd out the ferns.!!! Must be a climate difference ?? gary

It could be a climate difference as my area can receive up to a 100 inches of rain a year! Are your tree ferns mature specimens? On my larger ferns, the root system spreads out far. I have decided to put bromeliads under the fern as bromeliads dont really need dirt!