Inconsistent soil moisture
Crotons prefer to have consistently moist soil, but be sure to not over or underwater your plant. Be sure that your watering schedule is consistent–water when the top 2”-3” of the soil are dry.
If you accidentally let your Croton’s soil dry out completely, you may see some leaves drop. It will benefit from a good soak in the sink or tub to properly rehydrate the soil. Keep in mind that when the soil goes from bone-dry to saturated, it can cause stress for your Croton and cause leaves to drop. Give it some time to adjust.
Not enough humidity
Your Croton is a tropical plant, so it will thrive in more humid environments. Increase the humidity around your plant by misting the leaves on a regular basis, using a pebble tray, or moving a humidifier nearby.
Was the plant just moved, shipped or otherwise shocked?
Generally, houseplants don’t like change. They can be cranky for a few days or even a few weeks after they arrive at your home, or after a move to a new location within your home. Give your plant
some time and it will likely recover by itself if all other care requirements are being met.
Is it getting enough sun?
Your Croton prefers a sunny spot. If it’s placed in an area without adequate light, it will start to shed leaves. The color of your Croton’s leaves will also indicate if it’s receiving enough sunlight. Leaves will grow in mostly green and lack the vibrant reds, oranges, and yellow colors that Crotons are known for if it is in too dark of a spot.
Most of all, be patient!
Let nature take its course – if you’re seeing new growth, keep doing what you’re doing!