Tuesday, August 27, 2013

When to remove tree tubes

Probably the biggest area of confusion about using tree tubes is when to remove them.  The most frequent mistake tree planters make when using tree tubes is removing them too soon, before they have completed their task of successfully establishing a tree.

There has been a lot of discussion about this issue recently on sportsman's online forums.  A common complaint seems to be that the tree planter, eager to remove (and perhaps reuse) the tree tubes, removes them as soon as the trees emerge from the tubes - only to find that the trees are not fully self-supporting.  They "flop over."

Tree tubes designed to fulfill three functions at different stages of a seedling's development.

1) Establishment - tree tubes protect newly planted seedlings from deer, rabbit and rodent damage, reduce moisture stress to dramatically increase survival rates and accelerate growth, and shield them from herbicide spray and/or mowers to make weed control fast and easy (or even, in many cases, possible).

2) Support - the introduction of vented tree tubes and the adoption of flexible tree tube stakes such as pvc conduit has resulted in a dramatic increase in the stem diameter of trees when the emerge from tree tubes.  However, since we're still talking about growing a tree up through an enclosed space to rapidly pierce the browse line, trees that have recently emerged from tree tubes are quite thin-stemmed relative to their height.

That's why tree tubes - at least good tree tubes - are designed to last several years.  When the tree emerges the tree tubes assumes a new role, that of trunk support.  Tree tubes are meant to be left in place to support the tree while the newly emerged canopy sways in the wind and the trunk rapidly gains caliper.

3) Trunk/Bark Protection - A year or two after emerging from the tree tube the tree will be completely self supporting.  Even then the tree tube still has a role to play in the successful long term establishment of the tree.  Bucks love to scrape and rub their antlers against springy saplings.  Rodent still gnaw on the tender bark of young trees.  Treeshelters protect the trunk of the newly established tree from these dangers.

To gain the full spectrum of benefits tree tubes can provide, they should be left on young trees until they reach about 3 inches in diameter at the base, at which point the tree tubes should be removed and properly disposed of or recycled.

Does that mean you can't reuse tree tubes?  Not at all.  Given the cost of tree tubes - and tree planting in general - and the fact that most folks are trying to achieve as much as they can within very limited planting budgets, it is natural to want to establish more than one tree with each tree tube.

In the next post we will cover three methods for reusing tree tubes, and weigh the risk and benefits of each.

Monday, August 26, 2013

Tree Tubes on American Chestnut Trees

Tree tubes are finally fulfilling their promise as an establishment aid for American chestnut seedlings.

If ever there was a perfect candidate tree for tree tubes it would seem to be the American chestnut tree.  Billions of majestic chestnut trees were wiped out by the fungal blight that swept through its range in the early- and mid-1900s.  It has been the focus of heroic re-establishment efforts on the part of organizations such as the American Chestnut Foundation and thousands of dedicated scientists and volunteers.  Every chestnut seed or seedling planted is rare & precious, and critical to the long-term success of re-establishment efforts.  But chestnuts are also extremely vulnerable to all of threats to successful regeneration that other species face, including deer browse, competing vegetation and periodic drought stress.

So given the value and importance of each and every chestnut seedling planted and the number of threats they face, one would think that using plastic tree tubes on American chestnuts would be a no-brainer... and indeed American chestnut enthusiasts were some of the first tree planters to recognize the potential benefits of tree tubes and give them a try.  Unfortunately, the performance of those early, unvented tree tubes on American chestnut seedlings left a great deal to be desired.

It turned out that chestnut seedlings grown in tree tubes were particularly vulnerable to winter injury and die back.  They also grew with elongated, spindly stems that often formed a spiraling or helix growth habit as they worked their way up the tree tube.  Word of these issues quickly spread in chestnut growing circles, and chestnut planters either switched to using 2ft or 3ft tree tubes (shorter tree tubes provided rodent protection but did not cause die back or spiraling growth) or stopped using tree tubes altogether.

Growers of Chinese chestnut trees, incidentally, experienced and reported these same problems, and many became disillusioned with tree tubes.

Recently, however, chestnut planters - both of American and Chinese chestnuts - have recognized the major advancements in tree tube design - most notably the addition of ventilation, better light transmission properties and larger tube diameter - and have given them another try.  This time around the results have been outstanding.

In this blog I have often discussed the evolution of tree tubes as the story of two eras:  Before Venting (BV) and After Venting (AV).  The entire history of tree tube use and effectiveness in North America can be divided into these two categories; the un-vented tree tubes that first came over from the UK and worked well in their moderate and very forgiving climate, and the vented tree tubes that work in the extreme climates - both cold and hot - found in the United States.  Nowhere is this dichotomy of BV versus AV illustrated more starkly and dramatically than with American and Chinese chestnut trees.

In coming weeks we will be posting accounts and photographs of tree tubes on American chestnut and Chinese chestnut trees.  Healthy, rapid growth and straight trunks have been the rule, as you see in dramatic fashion here:

(Click to enlarge)

This is a Chinese chestnut tree growing in Mississippi.  It was planted in July, 2012 as a 12 inch seedling.  It was protected with a 4ft tall tree tube, and was watered to help it survive the late season planting.  It didn't put on any additional growth for the remainder of the 2012 season.... in other words in entered the 2013 growing season 1 foot tall.  This photograph was taken in August, 2013.  The tree grew more than 8 feet in one growing season.

More important than the rapid rate of growth:

1) The tree - and many others like it in the same planting - is perfectly straight, with no sign of the spiraling growth seen in the early days of chestnut seedlings in un-vented tree tubes.

2)  The trunk diameter - while thin relative to it (amazing) height, as you'd expect with any tree tube grown seedling - is very robust.  This also due in large part to the adoption of flexible tree tube stakes such as 1/2" schedule 40 PVC, as was used here.

Note: That "tray" at the base of the tree is a revolutionary weed mat developed in Israel called the IrriPan Weed Mat.  It blocks weeds, captures rain water and funnels it to the tree, reflects light up to the tree, and recycles soil moisture.

Follow this blog for more upcoming posts chronicling the use of tree tubes on American and Chinese chestnut trees.