Ah! Great question! Let's talk roots. Trees have different kinds of roots, such as lateral roots and tap roots. What they do depends upon the species, their gr

Ah! Great question! Let's talk roots. Trees have different kinds of roots, such as lateral roots and tap roots. What they do depends upon the species, their growth patterns, and how those patterns adapt to their native environment. Many trees will send out some lateral roots, and depending upon the species, they can be invasive. In the Sonoron, the mesquite is very aggressive about both lateral roots (far exceeding the drip line of the trees) and deep tap root (some mesquites have been discovered with tap roogs going 250 ft in the ground). They also have the added advantage of being a nitrogen fixer. Fig roots are invasive, though primarily lateral, shallow roots. Jujube (and all buckthornes) are invasive, sending roots that can then grow and pop up as a whole other tree! Mulberries, particularly the Pakistan varieties, also have vigorous, water-seeking roots. Bamboo are not trees. They are grasses, and grow like grasses with rhizomes. Once established, at around year 5, you would have a running bamboo grove pop up out of nowhere (because they can grow 1 foot a day until they reach their maximum height). As far as basins, a basin is any depression in the landscape where rainwater can pool. It can be shallow, or deep. Many of the greenways here in Phoenix are large basins that can collect and help absorb our monsoon rains. What you are talking about with girdling happens with hardwood trees, and not with "basins". When planting a bareroot hardwood tree, you should not plant it in a way so that the root crown goes too much below the ground level. The roots need to be unravelled so that they can grow outward instead of forced back on its self. For hardwoods, they can and do strangle themselves if their roots are allowed to girdle. Contrast that to a fig, whose roots will go whichever way and it will be fine. Knowing that, you can still create a basin for such trees. You would dig the basin as a ring much further away from the hardwood, possibly as a shallow basin.