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Friday, March 18, 2011

A Less-Than-Ideal Potted Tree? Even Natives Can Have Problems.

Last August I ended up with a mistreated winged elm (Ulmus alata). This interesting tree, native from north central Florida northward, has corky extensions on its branches, which is why it's called a "winged" elm. The branches make it a good addition to your landscape for its year-round interest. It had been headed back at least twice and branches were coming from everywhere.

This is why you rinse away all the soil
from a potted tree.

The first thing I did was water it in its pot, but when I was ready to plant it I rinsed ALL the soil from the roots. (Who knew that they'd be so red?) There are several reasons for this:
1) If the tree has been sitting in that pot for a year or more, there are virtually no nutrients left in the soil.
2) Many times trees that have been potted and repotted are too deep in the soil. Rinsing the soil away will reveal the root flare and this should be at or slightly above ground level when planted.
3) Trees sitting in pots too long have circling roots that may eventually strangle the tree as it grows. In this case the circling roots did not show when I removed the plant from the pot, because it had been previously repotted into a larger one.

I dug a wide shallow hole and used no soil amendmentsjust the native sandy soil in that spot. I untwisted the roots as gently as I could, but two largest ones cracked. The smaller roots were easier to spread out as I placed the tree into its hole. I flooded the hole with rain barrel water and added the soil around the roots and gently tamped it down so the tree was vertical. I built a low circular berm around the tree to form an 18-inch diameter saucer to keep water from running away.

I watered the tree with a 2.5-gallon watering can every day for two weeks and then I spread a generous top-dressing of compost at the edge of the original planting hole and topped it with wood chip mulchbut leaving a few inches around the trunk without any mulch.  After that I watered several times a week for the next month and at least once a week until the end of October.  By this time the tree had lost its leaves. Through the winter, I didn't know whether my poor little elm had survived or not.

Spring greening of the transplanted elm.
At the end of February, a mass of new green leaves had sprouted. Yay! The tenacious elm had survived the transplanting brutality.

Even though the branching was chaotic, I didn't prune it at all last fall.  A new transplant needs all the energy it can getthe more leaves the more photosynthesis and the more energy for regrowing a root system.

One old gardeners' tale is that you prune trees upon transplanting so the roots don't have so much to support. This may seem logical, but the generous irrigation keeps the plant from wilting and then it has significantly more energy for recovery.

But now that the elm is growing, it's time to start the gradual process of converting it to a single-trunked tree. It's gradual, because trimming too much could be a harsh setback to an already stressed plant.

The tree trunks lean against each other.
I chose the straightest and most vigorous
leader to be the single trunk.



















After deciding which trunk will be "The One," I trimmed back about one third of the lengths of the other two.  Later I'll trim back these doomed leaders by half and by the third session, I'll trim them all the way back to the trunk.

After trimming: The main leader looks like it's forked,
but in reality the closest branch is thicker and straighter.
The side branch will be pruned back next time.
 From this photo it looks like my chosen leader is a Y with equal forks, but there is one strong leader here and the next trimming will include chopping back the side branch so that it doesn't become a second trunk. After the top branches are trimmed, then I'll start cutting back all those small branches arising from the lower part of the plant.

Standard pruning recommendations are that you should not trim more than 20% of a tree's canopy in one season.  And with a stressed tree like this elm, less than 20% is a good idea.

To be continued...

University of Florida horticulture professor Ed Gilman maintains the Landscape Plants Web site, with detailed information on the care of woody plants: http://hort.ifas.ufl.edu/woody.
See especially all of the sections on tree establishment http://hort.ifas.ufl.edu/woody/establishment.shtml , including on amount and frequency of irrigation after planting http://hort.ifas.ufl.edu/woody/irrigation2.shtml.



Ginny Stibolt, still learning about Florida gardening

1 comment:

  1. For an update on this little tree see http://nativeplantwildlifegarden.com/natives-plants-for-your-yard-the-next-step/

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