Your tree should be planted in a container and placed outdoors in full sun. Most citrus such as lemons will withstand temperatures down to 32°F, and even 30°F, without sustaining damage. There is a balance to be struck in winter as exposure to cooler temperatures makes the fruit sweeter and the skin thicker. While citrus can be grown indoors in a sunroom, there will be fewer problems with insects if the plants are kept outside, at least during spring, summer, and fall. Additionally, pollinators, such as honeybees, are outdoors and ensure pollination of the flowers so that fruit is set. However, citrus needs to be brought inside (to the garage, for example) when temperatures go below 32"F. You may wish to invest in a sturdy stand with heavy casters on it or a plant-moving dolly in order to facilitate moving the plant in and out during fluctuating winter temperatures. When potting up citrus make sure the potting mix is well- drained as the plants are adapted to growing in sandy soils.
Organic fertilizers formulated for citrus, such as Citrus-Tone, are best for your citrus trees, and they will benefit from the trace elements in the organic fertilizer. Use once per month at a rate of 1 teaspoon per 3" pot diameter or according to label directions. Additionally, an iron supplement, such as Iron Safe, should be used once per month. These will keep the foliage green and healthy and help ensure optimum fruit production.
Citrus trees store water, in part, in the fruit so frequent watering is needed to produce good fruit. Try not to let plants dry out or remain constantly wet. You may find it helpful to mulch over the top of the soil to reduce water loss and keep the roots insulated. Just make sure the mulch doesn't rest against the trunk of the tree.
The best time to prune citrus is after harvesting the fruit. On older trees, prune the branches that produced fruit by about one-third. Suckers that appear below the graft union and water sprouts (thin vertical sprouts produced on lateral branches) should removed anytime you see them.
Aphids, scale, and spider mites are sometimes seen on citrus trees, especially if they are stressed or are not being grown under ideal conditions. All of these can be treated with horticultural oil. Insecticidal soap can also be used on aphids. Mite-X is an excellent organic control for spider mites. Scale must be treated with horticultural oil. Avoid spraying horticultural oil when temperatures exceed 85°F.