Monkey Puzzles grow in the wild on volcanic slopes in Chile and southern Argentina. As such these very hardy conifers are extremely well suited to the UK climate but they do grow into very large freestanding trees!
In Cornwall you see them growing in maturity in many towns and villages. This is because the Lobb brothers brought the seed back from South America in the 1840s and Treseders Nurseries, based in Truro, sold the plants from a pony and trap travelling around the countryside. At Burncoose there were two specimen trees measured at over 100ft in height in 1930. One died of old age recently. The other survives still at this sort of height.
The key thing to understand is that normally these trees are either male or female. Only very occasionally will a tree produce male and female flower cones on the same tree. Therefore, if you wish to grow fertile seeds on a female tree, there needs to be a male tree reasonably nearby. At a young age it is impossible to determine if a seedling is male or female so, if you do have room to plant two future specimen trees, you will have to trust to luck as to what sex they turn out to be!
Female trees produce edible seeds.
Male flower cones are produced on egg-shaped cylindrical catkins 3-5in long. The pollen sheds in July. Female flower cones are ovoid and larger, and they take two seasons to develop. They appear in the spring of one year and shed their seeds in August or September of the next. Once your tree flowers, in perhaps 15 to 20 years after planting, it is then fairly easy to determine whether it is a male or a female.
Monkey puzzles start life with a conical shape but, in maturity, the lower branches die off to leave a clear stem and a rounded top. The bark has horizontal ridges and the circular arrangement of the leathery dark green leaves with sharp spikes gives this tree its common name.