Why is my plant not growing? It’s still in the original pot (12 inch), it was full when I bought it. Now it’s very sparse and when new leaves start to grow (they usually grow to about 12-13 inches) they quickly die turn brown and die.
Sparse, weak new growth is often caused by a plant’s not getting enough light. Philodendron selloums need to be very close to an uncovered window, but also protected from the sun shining directly on its leaves for more than 2-3 hours per day. Too much direct sunlight can cause leaves to burn.
But light may not be the problem. When new leaves come in and are discolored or distorted that is a good indication of a root/watering problem. Improper repotting is often a cause, but you did not repot so that is not an issue.
You are probably either under or over watering. You should wait until the top half-inch of soil feels dry before adding any water. Then, water slowly over the entire surface of the soil until a bit of water trickles through the drain holes and into a saucer. Don’t water again until it reaches that level of dryness again.
So, make sure your plant is getting proper light (lots of bright indirect sunlight) and water your plant as needed. Avoid repotting and fertilizer as both of these will aggravate the problem.