The Boston Fern is a fascinating plant. Being easy to grow and care for makes them the ideal specimen for hanging baskets on porches, balconies, and in containers in any part of the garden to instantly add a subject of interest.
The bonus for growers fascinated with ferns is that the Boston Fern does not need high levels of light, so it can be enjoyed year-round, and indoors.
Of course, to have it looking all prim and proper all year round, indoors, out, or in a combination as they are often moved between locations, you need to know how to adapt your outdoor or indoor fern care when any symptoms of problems emerge.
Symptoms of Problems on Boston Ferns
Naturally, when you have concerns that your Boston Fern is struggling, the symptoms are indicators of the problems that lead to finding the right solution.
The most common symptoms Boston Ferns presents with are…
Graying Greens and Yellowing Fronds
Discoloration of the fronds is a telling sign of a problem.
Graying is common. It happens when the plant does not receive enough water. The longer the soil is dry, the slower the plant grows and the grayer the leaves become.
When the discoloration goes beyond gray to lighter greens, yellowing, and browning, that is a symptom of a pest problem or a disease that will need intervention to treat the problem.
Long, thin, and drooping fronds are not what you would have in mind for a pretty fern in a hanging basket. The higher the light intensity these get, the lighter the greenery becomes.
Dark green fronds are an indication of low light levels. Without sufficient light, the fronds start to hang down straggly. Like they just fell over the side hanging loosely.
Restore the color by increasing the light levels. These are considered by some to be among the best low-light indoor plants, but that is because they can tolerate it. They need moved on occasion to brighter spots for optimal growth.
Boston ferns are technically medium light plants requiring at least a couple of hours of indirect sunlight daily. Never in a southern facing position as the sunlight is far too intense.
Fronds drooping and accompanied by discoloration is a symptom of a larger problem. Either disease or a pest feeding on the plant.
Runner Burn and Leaf Tips Browning
When the fronds on a Boston Fern turn brown, sunburn is the likely cause when it is exposed to direct sunlight for too long. When that is not the case, yet you still see runners burn and the leaf tips brown, the cause is more likely to be an excessive salt accumulation.
Boston Ferns do require some plant food to keep them growing healthy. Some growers use fertilizer to speed up the growth rate of Boston Ferns. When it is used, it needs to be done sparingly and reduced in the winter when this plant naturally slows down growing.
The salts from fertilizers will build up in the soil so an occasional flush is required to leach the soil of excess salts, or else later, as a fix for fertilizer burn.
These can come from fertilizers, perhaps even the type of water in some areas that are too hard for plants, or a chemical treatment applied to treat the plant for pests.
Phytotoxicity is a term used to describe an injury to plant tissue that is contributed to by the proper (or improper) application of chemicals.
The chemicals may protect the plant in the short term, but the longer residual reaction can result in phytotoxicity. This can manifest as browning on the leaf tips and runner burn on the fronds of a Boston Fern.
The fix is to either flush the soil or repot it in a fresh potting medium.
Boston Fern Diseases
Pythium Root Rot
Pythium root rot is more likely to occur when two growing conditions are off. Low light levels and high humidity. It encourages the fungal pathogens to develop and quickly spread throughout the root system of the plant.
The symptoms are strikingly clear. The fronds turn yellow, sometimes gray, wilt and the plant becomes extremely frail, fast. Growth will be stunted.
When you suspect this to be happening to your plant, remove it from its container to examine the roots. What to look for are dark brown roots. They will feel mushy and squash easily when pressed.
On the lighter brown roots or rhizomes, Pythium fungi may be observed as a gray water-like lesion on the root. This fungus will attack the root and cause it to rot.
The only ball-like structures you should ever see on the roots of Boston Fern plants are nodules (bulbils).
These store water and release it when the plant needs it during drought periods. Do not remove nodules from the rhizomes they are attached to. They are important to the plant.
Nodules on Boston Fern are brown in color. Gray spots are indicative of Pythium root rot.
If there is a high amount of rot already happened, it is possible to propagate a dying Boston Fern by planting a healthy rhizome that has a few nodules attached to it in a fresh (and sterile) potting medium.
Rhizoctonia Root Rot
Rhizoctonia is a fungal disease that infects and spreads rapidly in soil. It attacks plant roots. However, the symptoms first start on the fronds of a Boston Fern.
The symptoms of a Rhizoctonia fungal presence first appear in the crown of the plant, and towards the top. If you aren’t aware of the issue, it can cause it to be mistaken as blight.
Other terms that this disease are known by include Rhizoctonia Aerial Blight and Web Blight. For simplification, it is root rot caused by the Rhizoctonia fungi, a soil-borne disease.
This is more prevalent in the summer months when humidity is high and the crown of the plant is wetter than usual for longer.
Irregular brown blotches appear on the fronds sporadically. These tend to emerge closer to the crown where each frond joins the stem. It spreads quickly and the brown lesions eventually form into what looks like a brown web-like structure making it look like a foliage problem, rather than root rot.
The main problem is the Rhizoctonia fungi in the soil. The only way to save a dying plant from root rot caused by Rhizoctonia is by repotting the plant in a sterile fresh potting medium and sanitizing the remaining healthy roots, rhizomes, and nodules before re-potting.
Pests that Cause Problems on Boston Ferns
The main pests that damage Boston Ferns are insects that pierce the foliage, and those that can bury themselves in the soil to access the roots.
Common pest insects on the Boston Fern include mealybugs, fungus gnats, spider mites, scales, thrips, whiteflies, and caterpillars. In many instances, pests are just that. A plant pest. The Boston Fern (provided it is in good health), can cope with most of these in small doses. Infestations are when you need to intervene.
Pests that Make your Boston Fern Sticky
These are the ones that cause the most damage because they excrete honeydew, and block sunlight, and that leads to sooty mold, and a quick demise of your plant when it can’t feed itself through photosynthesis (when sunlight can’t reach the leaves). What happens to plants without sunlight? They die!
Sticky plants are a strong indicator of a pest problem.
These are the most common pests Boston Ferns need to fend off…
A few flying insects tend to hover around Boston Ferns. Whiteflies do cause direct damage. Black flies (including the fungus gnats and shore flies), do not cause direct damage, but they do drop larvae into the soil, which can deplete the plant of nutrients, resulting in stunted growth.
The main flying insect that will damage a Boston Fern is the whitefly. These congregate on the underside of leaves, pierce the foliage, suck the sap, and then leave excrement on the fronds. The excrement is referred to as honeydew and it is what makes the fronds on your Boston Fern sticky.
Sticky Boston ferns are likely to have insects feeding on the underside of the leaves. Whiteflies are easier to identify because they fly off the plant whenever they are disturbed. Flick a frond and you’ll see a cloud of whiteflies emerge if they are present.
Mealybugs feed on the leaf axils of plants. These look like tiny blobs of white cotton. Rarely do they move. Rather, they stay in place and chew holes in the leaves of plants to feed on their juices.
Like all leaf-piercing bugs, these secrete excrement on the leaves, coating them in honeydew (attractive to ants), and that also blocks light from reaching the leaves.
As a sidenote, if you have ants on your plants, you likely have aphids or a similar honeydew excreting pest.
Sooty mold is a secondary disease that appears if insect infestations are not treated. If any of your plants are attracting ants, it is another pest that is causing the problem. Ants do not feed on plants.
Scale insects can be tricky to identify on any fern because they look much like the reproductive spores that appear on the underside of the fronds. Most scale insects are brown and around 1/10th to 1/16th of an inch. Reproductive spores tend to be larger and more uniform in appearance.
Scale insects feed on the plant, depleting it of nutrients.
The young scale bugs are the crawlers that move slowly across the fronds. They then insert the mouthparts into the frond to begin feeding. The legs enclose under the hard shell making it look it a brown spot on a leaf.
The usual symptom that accompanies a scale presence is yellowing fronds that eventually drop from the plant.
To get rid of these, scales need to be picked or scraped off each frond they are attached to.
Rasping Insects that Cause Problems on Boston Ferns
Rasping insects cause similar damage to those caused by leaf piercing bugs. Just not quite as damaging nor as fast at deteriorating the plant.
The reason for the slow demise of the plant is that rasping pests only feed on the top layer of leaves.
In this category of pests are mites, slugs, snails, and caterpillars. Their eating behavior is limited to the top layer, which is stripped away leaving behind holes.
Indications of rasping insect feeding are multiple small holes, often starting at the leaf edges causing leaf curling to happen. As many of these rasping insects are crawlers, rather than flyers, there is usually a silvery trail left behind on the leaf.
Root Lesion Nematode(s) Will Kill a Boston Fern
This is the one hidden destroyer that is the most difficult to detect. The symptoms appear very similar to Pythium root rot so if you have tried to treat it with a fungicide and still seeing damage progressing, know that a nematode presence in the soil is a possibility.
This is a type of soil-borne nematode that will attack the root system of some Boston Fern species.
There are two ways you can treat the Boston Fern for suspected lesion nematodes. The first is to release a batch of beneficial nematodes into the soil. These will eat the pests that are destroying the roots, but will not turn on your plant when they are done.
Another method for Boston Ferns either potted or in hanging baskets is treating the soil with a nematicide, which works the same as an insecticide, only it targets parasitic nematodes specifically.
For ferns in garden beds, soil solarization may be the more practical approach to rid the soil of all nematodes, however, soil solarization will kill all nematodes, including the beneficial ones.