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E-Newsletter -

May/June 2013 Issue

Snow damaed arborvitae"...a better-adapted hedge plant for the money. Arborvitae are relatively inexpensive and they're good plants - we've never treated a single one here for insects or disease." Arborvitae also create a nice, solid green backdrop for other plantings.

 

Repair or replace?

How do you know whether to try to repair a damaged arborvitae or just give up and replace it? Jeff says, "If there aren't any major trunks or branches broken, you can try tying branches in place with twine to see how they shape up this growing season." First, prune out any broken branches, then gently tie the sprawling trunks together on the interior of the plant using a biodegradable twine. If you train the branches to go back into shape, by the time the twine rots away the wood usually regains strength and holds its form. If major branches are broken, like in this photo, or the tree looks like it will never have a pleasing shape

again, it's best to replace it.

Arborvitae labelThe right plant

After seeing how different arborvitae at Olbrich held up to the heavy snowfalls this year, Jeff recommends some damage-resistant cultivars. He says two cultivars of our native eastern arborvitae (Thuja occidentalis) fared well. 'Hetz Wintergreen' and 'American Pillar', two relatively recent cultivars on the market, held up very well. Another recommendation is the western arborvitae (Thuja plicata), which is much larger at maturity than its eastern counterpart. A nice smaller growing cultivar (but still quite large compared to the eastern arborvitae) that you might want to try is 'Grovpli', Spring Grove®, it is readily available this year at local garden centers and nurseries. In addition to the eastern and western arborvitae, there is an excellent hybrid cultivar available, Thuja x 'Green Giant'. It's a fast growing tree that grows large like the western arborvitae. Jeff adds, "These are all so much better because they keep one central trunk that sheds the snow better than multiple

trunks which tend to splay apart under the weight of the snow."

Rose Garden HedgeMost arborvitae like sun, but will tolerate some shade. The most shade-tolerant is the western arborvitae. An additional nice feature of the western arborvitae is that it's deer-resistant.

New Rose Garden hedge

Olbrich's staff and volunteers recently replaced a large hedge of arborvitae along the edge of the Rose Garden, planting 'American Pillar'. Since this is a fairly new introduction, it was hard to find plants of any size on the market, but Jeff hopes these shorter plants will fill out quickly, growing to a height of 5 to 6 feet within 3 to 5 years, with a mature height of 25-30 feet.

Easy planting

As trees go, arborvitae are easy to plant and fairly forgiving:

  • Arborvitae rootsCheck recommended spacing between plants on the plant instructions. To create a hedge in the Rose Garden, the new arborvitae were placed 3 feet apart. The 'American Pillar' spreads from 3 to 5 feet, so Jeff chose the closer measurement to make sure the trees fill in more quickly.
  • Dig a hole two to three size the diameter of the pot, and about the same depth.
  • If you're replacing another arborvitae, remove as many roots from the soil as you can. Jeff adds, "the nice thing about arborvitae roots is that they're very fibrous, so there are lots of smaller roots that can be more easily removed."
  • Arborvitae roots close-upTease out the roots with your hands so they're splayed out before planting, not growing in a circular pattern as they often are inside the container.
  • Plant the tree to the same depth it was in the pot. Jeff says here's where arborvitae are more forgiving, "Typically you have to be careful about planting trees too deep, which can cause early tree death. For a lot of shade trees, if they're planted too deep, the roots tend to grow back up, crossing the trunk and causing a 'girdling root'. Since arborvitae roots are so fibrous, they can even grow right out of the trunk and are less particular about depth."
  • Though these new varieties should have a single Pruning arborvitaetrunk, if there are any big side branches or extra leaders, it's best to trim them off when they're young. Just determine which is the center or strongest stem and prune off the extra one at the next outward facing branch.
  • Scoop out a well around the base of the tree, creating a small circular berm, encouraging water to flow towards the tree.
  • Mulch, mulch, mulch! This holds in moisture, keeps weeds out, and if you use Olbrich's Leaf Mulch, it adds nutrients to the soil as well. Just make sure to leave a little space between the tree trunk and the mulch. (Olbrich's bagged leaf mulch is available daily 10 a.m. - 4 p.m., while supplies last.) This mulch is used throughout Olbrich's gardens and Jeff credits the health and beauty of the gardens to leaf mulch.
  • Keep the tree well-watered, about an inch of water a week. Arborvitae can tolerate some drought but, remember, when they're young, the root system is small. In general, Jeff says water is the key with arborvitae, "The only thing you have to pay attention to is the water. Give them that and they'll be happy."

Volunteers planting arborvitaeSilver lining

Though replacing damaged trees and shrubs is extra work and expense, Jeff sees the bright side, "It gives us an opportunity to update the plant collection and introduce plants that are better adapted to our climate. This is a garden and a garden is a living thing - you're always changing it and planting new things. They say a garden is never done and it's true." And that's also what keeps gardening fun and interesting!

Olbrich Botanical Gardens is operated as a public-private partnership between the City of Madison Parks Division and the Olbrich Botanical Society.
Olbrich Botanical Gardens | 3330 Atwood Avenue, Madison, WI 53704. | Phone: (608)246-4550 | Fax: (608)246-4719