Some trees only become available for purchase at the store at certain levels:
Apple tree - level 11
Pear Tree - level 15
Mulberry Tree - level 17
Cherry Tree - level 24
Olive tree - level 28
Cocoa Tree - level 33
Orange Tree - level 39
Lemon tree - level 35
Peach Tree - level 51
Almond - level 57
Apricot tree - level 63
Plum tree - level 69
Wild Cherry - level 72
Pomegranate - level 75
Avocado - level 79
Walnut - level 82
Fig Tree - level 86
Quince - level 86
Grapefruit Tree - level 90
Carambola - level 93
Lychee - level 97
Mango - level 102
Passion Fruit - level 106
Longan - level 112
Coconut - level 118
Pitahaya - level 123
Guava - level 131
Breadfruit - level 138
Kiwi - level 141
Banana - level 149
Papaya - level 153