I've planted a lot of tree seedlings over the last 25 years, and almost all of them were protected by plastic “tree tubes” or shelters in the seedling stage. I highly recommend you use a shelter on every tree seedling you plant this winter, and here’s why.
The main function and advantage of these translucent plastic tubes is to dim available sunlight except at the top, which encourages the tree seedling to put energy into vertical growth to reach the open light at the top, just as a seedling would that is struggling to compete in the understory of a mature forest. I took the photo above through an actual tree tube to illustrate a seedling’s “view” from inside; in these conditions, the seedling will naturally “go toward the light.” Thus, the tube forces the tree to grow above the reach of browsing deer while also leaving behind ground-level shrubs, forbs and grasses that compete for light. Once the seedling emerges at the top of the tube into full sun, it then branches out and begins to form a full crown.
Tree tubes provide other advantages. They also protect seedlings and saplings from being rubbed by bucks, and they afford some protection from harsh weather conditions while also conserving moisture around the seedlings. Two different scientific studies, both conducted at Auburn University in Alabama, found significantly increased survival (nearly double in most cases) and vertical growth (double and sometimes triple the growth rate) in seedlings protected with tubes compared to non-protected seedlings.
My own non-scientific testing has shown the same results. In winter 2008, I planted several southern crabapple seedlings, including a few in my suburban backyard. I left a couple of the seedlings un-protected to see what would happen. The photos in the Gallery below tell the story (click on any one of the images to enlarge). After one growing season, the sheltered seedlings emerged from the tops of the tubes. In the second growing season, they branched out into fine-shaped crowns. Meanwhile, the seedlings without tubes started branching out at ground level instead of growing upward. They remained in the danger zone where deer browse on plants, and browse they did. As you’ll see in another photo, the unprotected seedlings were "hedged." Their branch tips have been bitten back, regrown, and been bitten back again so many times that knobs of scar tissue have formed at the ends of the branches. Neither vertical nor horizontal growth has been very successful.
Granted, when you can't grow unprotected tree seedlings because of deer browsing, you probably have a deer density problem and need to develop a doe-harvest plan or improve habitat quality (or both). This test occurred in my suburban yard in an area where deer density is high and hunting pressure is almost nil. But even one deer happening upon a young tree seedling can nip off most of this season's progress with a few bites. If you spent good money on quality tree seedlings, spend a few bucks more to protect each of them with a tree tube. A 5-foot tube will cost around $4 to $5 depending on quantity. Considering the survival and growth benefits, this is a wise investment.
Here are a few more tips based on my experience using tree tubes.
• Buy tubes that are at least 4-feet tall, and 5-footers are even better. Shorter tubes don't stop deer browsing.
• Both solid tubes and those perforated with air holes work fine, but I have found that some profusely branching species like crabapples will occasionally branch out through the air holes. Solid tubes might be a better choice if you have the option.
• When planting each seedling, countersink the bottom of the tube an inch or two in the ground. This may help prevent small rodents from entering the base of the tube and using it as winter shelter or "girdling" the stem of the seedling.
• In the South, fire ants sometimes use the bases of tubes for their headquarters. This probably doesn’t affect tree survival, but if it bothers you, fire-ant bait will fix the problem.
• Be sure to use the mesh covers that go over the tops of newly installed tubes. This prevents wasps from building nests inside the tubes, and trust me, these tubes are preferred wasp habitat. If you don't use the covers, you're likely to get an eyeful of wasps when you look down the tube to check your seedling.
• Stake each tube for support, and attach the tube to the stake with zip-ties. Once the tree emerges from the top, you may need to use cord and stakes to support the tree as well. It is not common, but sometimes the rapid vertical growth associated with tubes produces a somewhat weak trunk that may need extra support until it is strong enough to support the weight of the crown.
• Leave the tube on the tree after the sapling emerges. In fact, I recommend you leave it on until the trunk is almost, but not quite, filling up the tube. This maintains protection against rubbing bucks for the longest possible time. But don't wait until the trunk is filling and splitting the tube, as moisture and dirt can build up on the trunk, causing favorable conditions for diseases and funguses.
• If gypsy moths are present in your area, consult with your state forester for advice before using tree tubes. The tubes can provide shelter for moth reproduction.
• Wrap-around style tubes can be removed from trees intact and re-used. Non-wrap-around tubes will have to be cut off and cannot be re-used. Consider which you prefer when shopping for and ordering tubes.
If you make your tree seedlings “go toward the light,” they won’t be heading for the afterlife but for a bright future providing mast and fruit for whitetails!