Saturday, February 14, 2004

Q I need information on transplanting and caring for lemon trees. I planted seeds from a lemon in a pot several years ago, and now I have three trees, including one that is 5 feet tall. They need to be moved into a larger container, and I would hate to lose them in the process. Can you tell me how to go about transplanting them into new containers?

A. Lemon trees can be great houseplants as long as you have sufficient sun and room for them to thrive and grow. They perform best in full sun, which translates into a south- or west-facing window. You must have good sun for one of the seeds to have grown into a 5-foot-tall tree.

Lemon trees have attractive, dark green glossy foliage and the most wonderfully scented flowers. A blossom or two can perfume an entire room. If you have sufficient sun -- and the patience to pollinate the flowers with an artist's paintbrush -- you can also get edible fruits.

Lemon trees can grow into 20-foot-tall trees in an orchard situation, but will not get that large when grown indoors. Your plant may still need a fair amount of space. Although there are varieties such as Meyer's lemon (Citrus limon 'Meyer') that do not get larger than about 4 feet, it is impossible to know how big yours may grow because it was started from seed. It is likely that the seed came from a named cultivar of lemon, but because your tree was grown from seed, there is no guarantee that it will have the same characteristics as the parent plant.

As for transplanting your lemon trees, I would wait until late March when houseplants begin to respond to the longer days and stronger light intensity outdoors. Gently remove the soil ball from the container. Because three plants are growing in the container, it would be best to plant them into separate containers.

Examine the rootball to see if you can separate them without damaging any of their roots too badly. Start with the largest plant because it will need as much of its original root system as possible. If you cannot separate it without significant damage to the other two plants, use a sharp knife to cut the roots apart. Allow the 5-foot tree to keep the biggest part of its root system, even if that means sacrificing the smaller plants.

Select a container that is 2 or 3 inches larger around in diameter than the large transplant's rootball. Use a good potting mix that combines potting soil, sphagnum peat moss, perlite and vermiculite. You can mix an organic-based fertilizer such as Houseplants Alive! for Flowering Plants or a coated release fertilizer such as Osmocote 20-20-20 into the potting soil. Be sure to follow label directions as to how much to use -- more is NOT better. Avoid using quick-release granular fertilizers intended for use with outdoor plants.

Put a layer of potting mix in the new container so the plant will be planted at the same level it was growing at in the original container. Finish backfilling the container with the potting mix. Gently firm the potting mix around the transplant's rootball to stabilize it in its new container. Add more potting mix until the container is filled to within an inch of the rim. Water it thoroughly, until water drains from the drainage hole(s) in the new container. Repeat the process with the smaller trees, in smaller containers.

When we are well past the danger of frost in June, you can put the lemon trees outdoors. Start by putting them out where they will receive morning sun, and gradually move them to a place where they will receive good sun for most of the day. Be sure to move them back indoors before frost threatens.

When they are outdoors, your lemon trees may require daily watering. Feel the soil daily. If it is moist, do not water. If it is dry, water until water drains from the drainage holes in the pots. They should not need to be watered as often while they are indoors -- perhaps only once a week. Again, feel the soil to determine whether or not they need to be watered.

You should not need to fertilize during the first growing season if you have mixed fertilizer into the potting mix. Houseplants generally do not require fertilization during the winter months when they are not actively growing. Next year, you can use a water-soluble fertilizer such as Peters 20-20-20 or Miracle-Gro according to label directions when the trees start actively growing again.

Send questions to Sandy Feather by e-mail at slf9@psu.edu or by regular mail c/o Penn State Cooperative Extension, 400 N. Lexington St., Pittsburgh 15208.

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