Citrus trees are terrific for sunrooms. The glossy foliage looks great year round, and the scent of the blossoms can fill a room.
I'm often asked if you can grow citrus trees from the seeds in grocery store fruit. Yes you can, but the overall results may be disappointing and the trees will take many years to produce fruit. For better results, buy healthy plants that have been grafted onto special rootstocks.
Before you invest in a citrus tree, make sure you have a place in your home where the plant will be happy. Citrus trees needs a long day of sun and good air circulation. Placing the tree near a heating vent will cause the leaves to dry out and drop. In warm climates, place the tree on a rolling platform so that it can be left outdoors most of the time, bringing it indoors only when frost threatens.
The most common problems with citrus grown indoors are scale insects and leaf drop. Watch the plant closely for scale, since it is easiest to control when it first appears. If there are only a few, you can remove them with a sharp knife or fingernail, or you can rub them with a Q-tip soaked in alcohol. If you have too many insects to handle this way, spray the plant with Soap-Shield at 5-day intervals, or alcohol spray (4 parts water to 3 parts rubbing alcohol.) Any time you use an alcohol spray you should shade the plant for the day.
Leaf drop is usually caused by wide fluctuations in temperature. Try to maintain a constant temperature, both day and night.
When the soil is almost dry water the pot until the water runs out the bottom, but never leave the plant standing in water. Plastic pots are best for maintaining a good moisture level. In winter, water just enough to keep the soil from drying out completely.
Plants can tolerate humidity in the summer, but prefer a low humidity in winter. Luckily, the air in most homes is quite dry in winter.
Use a high-nitrogen liquid fertilizer. Mix it 1/4 strength and feed the plant weekly from mid-spring until late summer. Discontinue feedings in winter.
There are some very good varieties that will withstand a wider range of temperatures, but for most the summer maximum should be around 87F (30C) and the winter minimum should be 40F(5C).