Care & Harvesting Citrus
Keep a good layer of mulch around the trees, but spread it several inches away from the trunk. The roots are fairly shallow and extend well beyond the dripline, so water the entire root area. The trees should receive a deep soaking about once a week; the soil should dry a bit before the next watering.
When trees are young, they occasionally produce some over vigorous branches. Prune these back so the tree remains well balanced. Limit later pruning to removing dead, broken, and diseased branches; it can be done any time of the year. The nutrient most needed by the trees is nitrogen; mature trees need 1 to 1 1/2 pounds per year. Apply it in four portions throughout the year, or apply the entire amount 6 to 8 weeks before a bloom.
Lower branches of the tree help protect the trunk from sunburn; citrus bark is very thin and can be easily damaged by too much sun. It helps to paint the lower trunk and other exposed portions with diluted white interior latex paint or to wrap the trunks of young trees with tree wrap tape. If a tree suffers frost damage, wait until new growth starts to see just how much has been hurt, then cut out the damaged parts. Cutting too early could lead to more damage. You may have to wait 6 months to see the new growth.
Most of the major citrus pests and diseases affect commercial plantings, not home garden trees, so you do not need a preventive spray program as you do with some of the-other fruits. You do need to deal with some pests, though. Gophers can destroy a tree quickly and must be kept out. Check the leaves frequently for aphids, mealy bugs, and red spider mites. If they're present, spray the leaves frequently with a forceful stream of water or use an insecticidal soap spray. Scale can be controlled with a horticultural oil spray applied in the fall, when temperatures are moderate and trees have been well watered.
You usually can't tell if citrus is ripe by looking at it. When some of the fruit reach full size, taste them to see if they're ripe. Unlike most temperate fruits, many citrus varieties ripen over a period of many months and keep well on the tree even when ripe, so you're not faced with an enormous harvest all at once. Some will ripen a late summer crop from the spring bloom, others will take up to a year or more to mature, and some continue to bloom and fruit year-round. Clip ripe fruit off with pruning shears instead of pulling it to avoid damage to twigs.