10 Neat Things About Trees
2. When is a tree a forest? We are often amazed at the gigantic size of the famous redwood sequoias, but that's measuring only vertical growth. Since aspens send up shoots (ramets) that become new "trees", the largest aspen "trees" are actually huge forests that can cover tens of hectares. Once such near Salt Lake City, Utah is estimated to weigh over 5,000 tonnes, many times larger than the biggest sequoia.
3. Do trees talk to each other? Lots of people think so and some even say they talk to humans, but that's another story. In fact, while trees don't speak in comprehensible sentences, they appear to communicate through several different means. Some trees (elms come to mind) appear to exchange information and even nutrition through the network of mycorrhizae that populate their roots systems. Others (acacias) appear to be able to send either a chemical or an electrical message to fellows in their vicinity when they are under threat from a leaf-nibbling animal. And trees such as the black walnut certainly send chemical signals with a toxic substance called juglone that wards off competition from certain other plants.
4. Trees produce oxygen in exchange for carbon dioxide. A large tree puts out enough oxygen to sustain four people every day. On the other hand, it takes about 100 trees to capture and store one tonne (2,204 lbs.) of carbon dioxide in a year -- two reasons why we need more trees than people.
5. Pruning trees roots will not necessarily kill a tree, but don't go too far. Never cut more that 30% of the root system of a mature tree, which means leaving a minimum space of 1.2 metres from the base of the tree for those with trunk of 30 cm or more in diameter.
6. Tree roots grow in proportion to the size of its crown above ground. The roots of a paper birch, however, will spread at least twice the height of the tree. Elm roots have a similar range.
7. The idea that tree roots maliciously seek out your sewage system to exploit any cracks is only an urban myth. What some tree roots will do is grow more vigorously in areas where they encounter moisture and nutrients (wouldn't you?). If the piping has perforations or openings, then tree roots may grow in that direction.
8. Most tree roots, the fine feeder roots, exist within the top eight to 12 inches of soil. Trees with deep roots least likely to cosy up to your pipes and weeping tiles include bur oak, black walnut, common hackberry and some types of hickory. Trees that like dry conditions and so will avoid moisture-laden drains include beech, Black cherry, Black locust, European and Paper birch, Norway maple, many pines and spruces and Staghorn locust.
9. Trees can clean up groundwater contamination through a process called phytoremediation. Poplars and willows are particularly good at this. Trees can clean up contamination in three ways: One is by changing the chemical composition of organic contaminants such as PCBs through interaction with bacteria at the root level. Two is through a similar process with heavy metals such as mercury, but where the changed chemistry is them expired into the air through the leaves. The third is by taking the contaminants into the above ground growth and storing them. The recovery of heavy metals stored and reclaimed in this way is being studied in a process called phytoextraction.
10. Lilacs, elms, oaks and beeches can all live 200 to 300 years or more , common firs and spruces can live as long as 800 years, and sequoia are well known both for their bulk and their great age, but the champion grower is the pine, one of which, Pinus longaeva, has been clocked at 4,900 years. Long-lived trees generally grow slowly -- as slowly as just one inch per century!
From top to bottom: 1. Aspen leaves take out sting. 2. An ancient Oak in England. 3. Aspen trunks near Aspen, Colorado. 4. Eastern Elm. 5. Oak tree. 6. Phytoremdiation. 7. Tree roots.
Thank you again Ontario Gardener for such an interesting newsletter again. I enjoy them very much.