ZingW

I saw carved on a tree trunk an inscription dated 1920. It was very high up on the trunk. How do trees grow - from the top, the bottom, or both?

Flo, London

• Trees, like all plants, grow from groups of dividing cells called meristems. In trees these are usually at the tips of shoots, and at the tips of the roots. Meristems not at the tips produce branches.

  KJ, Oxford UK

• As a small boy in the 50s I helped my brother do a very classy carving on a mature Beech tree (nice smooth bark, inscription lasts for ever) in our grandfather's vicarage garden in Cornwall. We were sitting high up in the crown at the time, and Ive occasionally wondered since what the reaction will be when the tree finally comes down. Now I spend much of my working life inspecting and reporting on individual trees. On one occasion a passer-by saw me staring up at a supermarket shopping trolley that had been put in the top of a mature Horse Chestnut (being a few yards away from a nurses hostel, this was not quite as surprising as all that...). 'That would have been put there when it was a young tree and its been carried all the way up' he said knowingly. I nodded in agreement.

  Geoff March, Stroud, UK

• Jack Hill is wrong. Trees do not grow up from the roots. The new growth is at the tips of the branches. The buds we see in winter are the basis of the next seasons growth. The buds elongate and produce new branches. The branches and trunk increase in width by producing a new layer of sap-carrying cells outside the previous year's layer, just below the bark. The root system grows in the opposite direction, from the ends of the root tips.

  Mike Creasy, Cardiff UK

• As a young boy on my 5th birtday I got a new saw. I proceeded to cut down the first tree I saw, which just happened to be decorative tree in our yard bordering our neighbor. I cut down a small douglas tree at two feet above the ground. The dominant branch below the cut became the trunk, but left a very noticeable bend in the tree. As the tree grew the noticeable bend in the tree also rose along with the branches around it. It is now 32 years later and the tree is 50 feet tall and the bend in the tree is over eight feet above the ground. While trees most visibly grow from the edges, this is clear evidence it also has some growth at the trunk. By the same token the 1920 marker on the tree was quite likely done without a ladder.

  Rob Gibson, Duncan, BC, Canada