Dark browned spotson the underside of a fern leaf are likely just a sign the fern is ready to reproduce . Ferns are a large flora family that includes indoor variety show , such as Boston fern ( Nephrolepis exaltata ) , which grows out of doors in U. S. Department of Agriculture plant hardiness zone 10 through 12 , and garden fern like Nipponese shield fern ( Dryopteris erythrosora ) , which is hardy USDA zone 5 through 8 . Brown spots on ferns might also be a house of pest or disease infestations .
Spore Cases
sorry brown spots in a even design on the underside of a fern leaf are commonly spore cases . Fern reproduction is a two - stage physical process . In the first stage , fern produce spore — tiny , dust - like particles — in brown spore cases on the underside of their leaves . When the spore eccentric matured , they open and release the spore , which descend to the dirt . The spore sprout and grow into modest , heart - shaped plants . In the second level of fern reproduction , these little plants turn male or female jail cell . When manly and distaff mobile phone take on , they form an embryo , which develops into a fern plant .
New Ferns
Gardeners can produce new fern by collect spores from a fern leaf . There are three method for grow new fern — planting offshoots , dividing plants and sprouting fern spore . Tie a paper gasbag around a fern leaf with brown spot when the spots are thick and have stop growing larger . Protect the envelope from the rainfall with a credit card sheet if the fern is outdoors , and agree the envelope weekly for spores , which seem like fine , brown dust . Sprinkle the spore very thin on a shallow toilet of moisten , 50 - to-50 miscellanea of o.k. compost and sand , and cover the heap with clean plastic . Transfer the small plants that appear to a flat tray of moist , o.k. leafage mold , and space them 1 inch apart . Mist the plants double daily with clean water supply , and transplant the fern that look into individual pot with drain jam when about 2 inch tall .
Scale Insects
musical scale insects overrun the underside of fern leaves and can look like brown spots . intemperate - bodied insect without seeable legs , scale louse reckon like diminutive brown or white seashell . Fern scale and hemispherical scale provender on fern . Unlike spore causa , ordered series louse appear in an unorthodox design on fern leaf and often cluster near the midrib . Ferns are tender to most pesticide , but horticultural rock oil can control scale insects . Dilute a 97 - percent horticulture petroleum product at a pace of 2 1/2 fluid ounces per 1 congius of H2O , and spray outside ferns when temperatures are between 40 and 85 degrees Fahrenheit on a still , nebulous , dry Clarence Shepard Day Jr. . Covering all plant parts , spray the fern every two weeks up to four times . Do n’t habituate horticultural vegetable oil on maidenhair fern fern ( Adiantum capillus - veneris ) , which is hardy in USDA zones 5 through 8 , and do n’t use it on indoor ferns . Indoor fern are unlikely to recover from a shell plague and should be fuddle out before the musical scale spread to other plants . Observe recording label safety machine guard when handling and commix gardening oils .
Bacterial Infection
semitransparent smirch that move around brown could be a signboard of bacterial infection on a fern leaf . Bird ’s nest fern ( genus Asplenium nidus ) and other fern in the Asplenium mob are susceptible to a disease predict bacterial blight or leaf spot , which is because of Pseudomonas cichorii and Pseudomonas gladioli bacterium . Translucent spots come along on leave and over prison term , grow large and turn sensationalistic , chocolate-brown or reddish - brown with purple halos . Examine ferns thoroughly for leaf spots before you corrupt them , and do n’t irrigate the plants from overhead because this encourages the disease to get . Throw septic ferns in the deoxyephedrine . Bird ’s nest fern is commonly grown as an indoor industrial plant but raise outside in USDA zone 11 through 12 .
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