Lisbon lemons are one of two varieties of lemons that are considered "true lemons." All other varieties are considered hybrids of one of the true lemons. Lisbon lemon trees, which originated in Australia, grow fuller and denser than other lemon trees and are recognized by their upright branches that are covered in large thorns. Lisbon lemon trees bear fruit during the summer and fall, and the lemons grow inside the canopy of the lemon tree, rather than at the end of exterior branches like other lemon trees. Prune your Lisbon lemon tree at the beginning of each season to maintain its health.
Check the tree at soil level to see if any suckers are emerging from the root system. Suckers are small tree growths that resemble lemon tree saplings. Although they look like separate trees, suckers develop from the same root system and "suck" the nutrients away from the primary tree. Use gardening snips to cut suckers off at soil level.
Check for suckers at tree "crotches." Suckers often develop on the Lisbon lemon tree at places where two intersecting branches form a "V." Wear gardening gloves and a long-sleeved shirt to protect your skin from the Lisbon lemon tree's thorns. Cut off these suckers with a razor blade or a pair of gardening snips.
Remove sickly, spindly branches with gardening snips or sheers. Do this at the beginning of each season to keep the tree at optimum health. Spindly or sickly branches will not bear fruit, but they do sap the tree of some of its energy, which could otherwise be spent on fruit production on stronger branches.
Examine the tree for dead wood that died back during cold or freezing weather. Use gardening shears to cut the dead wood from the tree at the trunk or soil level.