I had a few indoor lemon trees. They were in the window, getting 4-5 hours of sun. They don’t seem to get past 7 inches high then the tops turn brown and they die. I have one left. What should I do to keep this final plant healthy?
From your description, it sounds like the plant may be suffering from nitrogen deficiency or overwatering. As well, you should check to verify that it has not been attacked by pests – this could also be a factor.
Here are some basics for caring for a lemon tree:
- It needs 4-8 hours of direct sunlight a day and likes temperatures between 60-70 degrees F [16-21 degrees C] (and no drafts). Temperature drops of 5-10 degrees F [3-6 degrees C] at night are fine.
- If it’s too hot, especially around the roots, the plant may drop its leaves.
- Soil that contains leaf mould, peat moss (to keep the pH relatively low – citrus plants like slightly acidic soil, pH 6-6.5) or compost is healthy for the plant. For example, 1/3 sterile potting soil, 1/3 peat moss, 1/3 organic matter would be a good mix. Make sure the soil drains well – soggy soil could rot the plant’s roots.
- Water thoroughly on a regular basis (as you would any houseplant), allowing the soil surface to dry out between waterings.
- In the winter, relatively high air humidity levels are especially important. Use of a humidifier would be helpful, as would placing the plant pot on top of a water-filled, pebble-lined tray. The bottom of the pot should not touch the water. As the water evaporates, this provides additional humidity to the plant. Another way to increase the humidity of the air is to mist the plant from time to time, in particular when flower buds are ready to open.
- Fertilize every 2-4 weeks with a fertilizer while the plant is actively growing (following manufacturer’s instructions). In the fall and winter, feed half as frequently. Note: If you can source a fertilizer made specifically for citrus plants, this would be a good option.
- Check for insects (e.g., mealybugs, spider mites) especially on the underside of leaves. [watch for leaves that are curled, speckled or yellowing, sticky material on the leaves and webs between branches]. If you find something suspicious, call your local nursery for advice on how to deal with these pests.
The following are helpful references:
- UCCE Master Gardeners of Orange County. Edible plants: Citrus, problems. Many of the problems discussed here relate to pests, but there is a link to a “Citrus problem diagnosis” table, and the last couple of entries relate to yellowing of leaves from overwatering or nitrogen deficiency.