Questions From the Potting Bench
The queries collectors send most often, answered briefly and precisely.
01Care and conditions
Why do my maidenhair fronds crisp overnight?
One dry spell at the roots is enough. Cut dead fronds to the base, keep the rhizome evenly moist and raise humidity; new croziers usually follow within weeks.
Is misting enough to raise humidity?
Misting raises humidity for minutes. For species needing more than 70% relative humidity, use a closed or semi-closed case or a humidifier on a hygrostat. See humidity targets.
Can I use tap water for ferns?
Many ferns tolerate it, but hard tap water leaves mineral deposits and stresses species from acidic habitats. Rainwater or reverse-osmosis water is safer.
Do filmy ferns need a sealed case?
In nearly all homes, yes. Their fronds are one cell thick and need 90–100% relative humidity with cool temperatures.
How often should I feed rare ferns?
Sparingly: a quarter-strength balanced liquid feed about once a month during active growth, and none in winter.
02Identification and propagation
What are the brown dots under my fern's leaves?
Usually sori, the spore-bearing structures, arranged in regular patterns. Scale insects are irregular, can be scraped off and often leave sticky honeydew.
How long do fern spores take to germinate?
Usually two to six weeks for a green haze, four to twelve weeks for visible prothalli, and one to three further months for the first fronds.
03Law and sourcing
Is it legal to dig up wild ferns?
In the UK it is an offence to uproot any wild plant without the landowner's permission, and protected species carry stricter penalties. Buy propagated stock.
Do I need a permit to buy a tree fern?
Cyatheaceae tree ferns are on CITES Appendix II, so international trade needs permits. Tasmanian Dicksonia antarctica trunks should carry a state-issued tag.
Not answered here? Write to the glasshouse.