A bill concerning the delivery of two trees in 1771 for Huys ten Donck reveals a specific method for the planting of magnolias. They had to be planted in the pot they were delivered in. After one or two years this pot should then be broken, while in the ground.
Philip Miller originally suggested to keep the plant in pots for the first two years (after sowing), so the tender young plants could be brought in when necessary during those first years. After that, they went into the ground, pot-less.
Apparently the succes rate of newly planted magnolias had been below expectation. Magnolias ranked under the most expensive garden plants of the time, so losing one of those was a costly and frustrating affair. Twenty-five years after the Dutch translation of Miller’s work was published, their planting method in the Netherlands had changed -probably as a result of that.