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LinkedInSun Burn to Grafted Trees
Field topworking avocados and citrus can be a prolonged process that can take two years of maintenance before the trees are productive. Often, it's easier and cheaper to just start off with a new tree. Thegrafted tree needs to be pruned back and buds or bud sticks need to be inserted into the old trunk. Birds love to sit on these new perching spots, and can often damage the bud stick, so they need to be protected with some type of covering like a paper bag. The latent buds in the trunk need to be constantly removed to prevent the old scion from outgrowing the new one.
A nurse branch also needs to be maintained so that there is a steady flow of transpired water to cool the trunk. Bud sticks are leafless and when the tree is headed back to graft, the tree no longer has the leaf area to pump water through the trunk. The trunk can heat up and result in sun burn damage. This damage may not appear for a year or so after the incident has occurred. It normally will show up on the south or southwest side of the tree, which catches the afternoon sun. The damage may be so severe that the tree dies, or the tree may begin a healing process as with other wounds and start growing callus tissue along the margins of the sun burn damage. If the damage is nor too extensive, the callus growth can eventually cover over the damage with new bark. If the grafted tree has left some structural branches, damage can show up on upper surfaces of branches, as well as those sides facing the afternoon sun.
To avoid sunburn damage, retain the nurse limb for about a year after grafting and whitewash or cover the trunk with a protective paper. Managing irrigation is important, as well. If grafted trees are interplanted with trees with more mature canopies, the grafted trees should be on a separate irrigation system and schedule. This is to avoid water stress which can enhance sun burn.
Sun burn can happen to any grafted tree, especially those with thin bark, like citrus and avocado. Any time a portion of the bark is exposed to sun that has previously been in the shade, can also set up the tree for sun burn. So excessive pruning going into summer months can also cause significant sun burn.
Sunken area of trunk, showing sun burn damage and callus growth starting to grow along margins of damage. Grafted citrus with nurse limbs and whitewash.
IMG 1956
citrus whitewashed and grafted
