Fiddleleaf Fig Care Prevents Diseases

Q. My fiddleleaf fig houseplant has brown spots on some of the leaves. I'm watering it every other week. I have looked but can't find the cause of these brown leaf spots. I thought it might be a fungal issue, so I applied liquid copper but that didn't make any difference. Do you have any idea what causes these spots and what I can do to help this houseplant?

I really appreciate it when I am sent so many pictures. This helps a lot in diagnosing the problem.Fiddleleaf fig, Ficus lyrata

A. Fiddle leaf fig has made a comeback. It used to be very popular 40 to 50 years ago. Now it’s on the rebound for interior designers as a houseplant.

            Fiddle leaf fig in the wild starts its life as an epiphyte, similar to orchids. Eventually they root into tropical soils and live their life as a small understory tree, strangling the mother tree. Which means it likes filtered and indirect light. It can tolerate periods of time without soil moisture as well.

            Brown spots on leaves can be a disease problem, particularly if they are closely associated with leaf veins. Plant diseases on houseplants are not common in desert environments because of our low interior humidity. 

            Insects feeding on these plants are a bigger problem. Inspect the plant for spider mites, scale insects, mealy bugs and fungus gnats living in the soil which can cause problems similar to diseases.

            Plant diseases are closely associated with the health of the plant. To improve its health, and ability to ward off diseases, make sure it gets adequate light, water and fertilizer. If you need to stake this plant so it stands upright in a container, it is a good indicator it has not been getting enough light in the past.

            Lack of light is a common problem for houseplants because of our dark interiors. Larger houseplants slowly decline, beginning around 6 months after they are plunged into dark interiors. Smaller plants decline more quickly. If they are large plants, they have enough stored food to live for several months before they decline.

            This plant requires placement near a bright window but not in direct sunlight. Once a month turn the plant so that different sides of the plant receive light.

            When temperatures are pleasant outside, place this tree in a sheltered area on the north or east side of the home under a tree. During this time, it can start building up its food reserves for that long, dark haul inside the home during summer months. Never place it in direct sunlight which damages the leaves and causes them to drop.

           Lift the container. It is dangerous to water on a schedule unless you are confident this schedule fits the needs of the plant. Watering of this plant can be withheld until the soil is quite dry. Instead, lift or tip the container to judge its water content. Water is heavy. Potting soil containing water is much heavier than dry soil.

            Use a pencil. Sticking the pointed end of a pencil in the potting soil can help judge the moisture content. Pencils slide into moist soil much easier than dry soils.

            User soil moisture meter. They cost about 10 bucks at any nursery or garden center. They are good for judging relative amounts of water but not exact amounts of water. This moisture meter will tell you if the soil is dry enough to water or if it’s still wet and should not be watered.

            Avoid using straight tap water. Our tap water has lots of salts in it. Instead, use distilled or reverse osmosis water and blended with tap water 1:1 or more dilute. Give it enough water so that one 4^th of the applied water comes out the bottom. This helps remove salts.

            Add fertilizer based on the growth of the plant. If the plant is growing rapidly, temperatures are warm and there’s lots of light, water and fertilize more often. Add a small amount of fertilizer to the irrigation water at every 3^rd or 4^th watering.

            Interior plants should be repotted every 3 to 4 years. This means gently lifting the plant from its container and shaving off a 1 to 2 inch layer of soil from the root ball on all sides. Use a sharp, sanitized knife. Disinfect the container and repot the plant using new potting soil.