I would like to explain why Rav Shach explains the Gemara in Avoda Zara 23 as referring to the trees that were planted before Avraham and then worshipped after Israel served the golden calf. Normally trees that have been planted for fruit can not become idols since they are like mountains and the sun and moon that  have no human hold on them. This in fact is the reason I am thinking the Gemara is referring to trees that were planted to be idols at the very start and then the land was given to Avraham. That would make them idols of Israel that need to be burnt. But Rav Shach explains this Gemara differently since the Gemara says the only reason the trees are forbidden is that Israel served the golden calf. In My way of looking at the Gemara that reason would be irrelevant. So to him it has to refer to trees that were planted before Avraham and thus became the property of Israel after the land was given to him. And then the Canaanites worshiped those trees and there was no objection from Israel since they too at that time had served idols. It can not refer to trees that were planted after Avraham since those would be owned by the Canaanites and thus be idols of a idolater and only need nullification, not burning.

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I would like to explain why רב שך explains the גמרא in עבודש זרה דף כ''ג ע''ב as referring to the trees that were planted before Avraham and then worshipped after Israel served the golden calf. Normally trees that have been planted for fruit can not become idols since they are like mountains and the sun and moon that  have no human hold on them. This in fact is the reason I am thinking the גמרא is referring to trees that were planted to be idols at the very start and then the land was given to Avraham. That would make them idols of Israel that need to be burnt. But רב שך explains this גמרא differently since the גמרא says the only reason the trees are forbidden is that Israel served the golden calf. In My way of looking at the גמרא that reason would be irrelevant. So to him it has to refer to trees that were planted before Avraham and thus became the property of Israel after the land was given to him. And then the Canaanites worshiped those trees and there was no objection from Israel since they too at that time had served idols. It can not refer to trees that were planted after Avraham since those would be owned by the Canaanites and thus be idols of a idolater and only need nullification, not burning.

ברצוני להסביר מדוע רב שך מסביר את הגמרא עבודה זרה דף כ''ג ע''ב כמתייחס לעצים שנשתלו לפני אברהם ואז סגדו להם לאחר שישראל עבד את עגל הזהב. בדרך כלל עצים אשר ניטעו לפרי אינם יכולים להפוך לאלילים מכיוון שהם דומים להרים ולשמש ולירח שאין בהם אחיזה אנושית. זו למעשה הסיבה שאני חושב שהגמרא מתייחסת לעצים שנשתלו לאלילים כבר בהתחלה, ואז האדמה ניתנה לאברהם. זה יהפוך אותם לאלילי ישראל שצריכים להישרף. אך רב שך מסביר את גמרא זו אחרת מכיוון שהגמרא אומרת שהסיבה היחידה שהעצים אסורים היא שישראל עבד את עגל הזהב. בדרך שלי להסתכל בגמרא, סיבה זו לא תהיה רלוונטית. אז מבחינתו יש להתייחס לעצים שנשתלו לפני אברהם וכך הפכו לנחלת ישראל לאחר שניתנה לו האדמה. ואז הכנענים סגדו לאותם עצים ולא הייתה שום התנגדות מצד ישראל מכיוון שגם הם באותה תקופה שירתו אלילים. זה לא יכול להתייחס לעצים שנטעו אחרי אברהם מכיוון שאלו היו בבעלות הכנענים ובכך להיות אלילים של עכו''ם וזקוק לביטול, ולא לשרוף.