A fern’s lacy fronds may look delicate, but these sturdy perennials tolerate neglect as long as they are planted in the right place. It’s hard to describe a typical fern because there are so many species, each with its own characteristics. Fern hardiness depends on the species, and their natural habitat ranges from tropical rainforests to arctic climates. Ferns need full or partial shade and moist, well-drained soil with plenty of organic matter. Few pests and diseases attack ferns, but you may occasionally see rusts, leaf spots or thrips.
Pale green color usually indicates that the fern is getting too much light. Transplant overexposed ferns to a location with at least half a day of shade. Few ferns can tolerate strong afternoon sunlight, even for short periods. Yellow, wilting leaves indicate that the plant is getting too much water. Some ferns thrive in wet, marshy conditions. Those that don’t may experience root rot in wet soil. If you don’t want to change the location, use raised beds or containers. If most of the fern’s roots are dark-colored and soft, the root rot is advanced to a stage where the plant will not survive.
Leaf Spots and Rust
Leaf spots are caused by bacteria or fungi. The yellow or brown spots can be any size or shape. Rust spots, which are also caused by fungi, are often covered with rusty-looking powder. Clip out affected fronds and try to keep the fern’s foliage dry. Use an organic fungicide labeled for use on ferns to treat rust, and follow the instructions exactly. Some fungicides are quite toxic. Read the precautions and store them in their original container and out of the reach of children.
When a plant is infested with thrips, you may not know that an insect is causing the problem because thrips are too tiny to see. Their feeding causes white, desiccated areas on the fronds, and they leave behind pellets of dark fecal matter. Use an insecticide labeled for use on ferns against thrips. Many insecticides damage fern foliage, so test it on a small area before treating the entire plant. Use the same precautions as for fungicides.
Ferns grown indoors are sometimes bothered by spider mites. Pale or bleached fronds and webby material on the undersides of the fronds indicate a spider mite infestation. Isolate the plant to prevent the mite from spreading to other plants. Clip out badly infested fronds and give the fern a shower twice a week to remove dust and dislodge insects. The insecticides normally used to treat spider mites damage ferns, and this makes them very difficult to kill. Consider discarding the fern if you can’t get the infestation under control.
- The Perennial Care Manual; Nancy J. Onda
- The Complete Houseplant Survival Manual; Barbara Pleasant
- Rodale's Landscape Problem Solver; Jeff Ball et al.
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