Excellent work on researching - how does one pronounce cotyldons?
Don't mean to be a pain EB - but where have you got this info from? I had previously been advised by Peter Coppin (horticulture consultant) that most eucalypts with the exception of a couple do not have tap roots. When he says tap roots, he means roots that go down 30m for the purpose of maintaining the upright nature of the tree and not as a food source. He says that the important roots for nutrient uptake are in the first 600mm of soil. Hence why I ask the question when planting trees do we need to improve the soil beyond this point?
From looking around on the web I never been able to ratify what he has said, however he has claimed that most people believe that all euc's have tap roots and that it is a fallacy - so I guess from this accusation most literature out there would not support it.
What I have found is"
It is claimed that eucalypt trees absorb more water from the soil than any other tree species. The uptake of soil water depends mainly on the architecture of root systems and the depth of root penetration (Lima 1993). The capacities of the more than 600 eucalypt species for water uptake vary depending on the type of root system; some have superficial root systems and others have deeper systems (Jacobs 1955). As in most natural forests and forest plantations, the roots of most eucalypt plantations are concentrated in the superficial layers of the soil (Reis et al. 1985). However, some eucalypt roots can grow to 30 m in depth (Jacobs 1955) and extract water from 6 to 15 m deep (Peck and Williamson 1987)."
from
http://bioenergy.ornl.gov/reports/euc-braz/eucaly2.htmlI have eucalypts on the property but don't really care that much to dig one up to find out! It is more of an interest in probing what people out there believe based on accusations of a fallacy from one person.
I don't have an opinion/belief either way.
FJ