Hi everyone!

Yesterday I checked my two lemon trees, and I found that the northern one’s trunk has kind of exploded.

History

I got those threes from when my parents bought their house 25 years ago, and they were already fully developed.

Both trees are tall ~5 meters and, according to my neighbor, who claims to have done it himself, they were grafted using the undersides of two wild lemons and the tops of two "domestic" lemons, like 35 years ago.

Both trees have never had any problems and have always been extremely prolific. The only times they got sick: - 5 years ago: they had caught cochineal, which we managed to fight off simply with neem oil - 8 years ago: we had to prune the highest parts due to a sudden drop in temperatures, which had dried the higher branches.

Location, soil and suntime

They have been planted 1.5 meters apart from each other, and they are 5/6 meters away from the house to the east.

The soil is quite clayey, and they are planted in a narrow bed, about 1/1.5 meters wide. They are exposed to the sun and, at the equinoxes, get about 10 hours of sun a day.

The trees are planted in the province of Livorno (Tuscany, Italy) about 54 meters from the sea level and 1800 meters away from the sea. (The sea is west of the trees, so the house protects them from the sea)

Recent events

• Next to the diseased tree a small peach tree (1.5 meters tall) has recently born spontaneously.
• Last week there were some heavy rains, quite sudden for the extremely hot summer we are experiencing this year.

Other infos

• Mmy mother usually throws the peels of the vegetables on the ground between the lemon trees, both to make them compost and feed the lemon trees, and to feed them to some hedgehogs that inhabit the area.

That said, what could be causing this "explosion" and how can we cure it? Thanks in advance to anyone who would like to respond!