I have a fairly well established fern which recently started drying out regardless of frequent watering, to the point where there was nothing green left on it. I went away for a week and when I came back a new frond had come out fully green and healthy looking, with another not far behind. Now the new growth seems to be wilting pretty badly again. It has been pretty hot but I'd think it's still getting enough water.
It is likely that the roots of your plant have grown to occupy the entire volume of soil in the pot. There is no soil left to retain moisture.
You can check this by popping the plant out of its pot. If all you see is root then it is time for a larger pot.
- Purchase a pot one size larger than the existing
- add fresh soil to the bottom of the new pot.
- Remove the plant from the old pot
- make a series of shallow cuts in the root ball from top to bottom. This will allow new root growth to start growing in the new soil.
- Place in the new pot, add soil, water and you are good to go.
Probably a good time to check for scale on the underside of the fronds. Scale looks like little brown bumps but should not be confused with the brown flat areas on some leaves where spores are produced.
Consider investing in a self watering pot as this will provide a moisture cycle more suited to ferns. They tend to like not too wet, not too dry, just moist all the time.