Sunday, September 25, 2011

Popcorn Anybody?

Well, yesterday was the Fall version of the annual North Charleston Plant Swap. It was a smashing success with 90 participants and over 2000 plants swapped. During the setup phase, all was well....until.
The Clemson Extension Agent, who was there to participate, came up to me and said, "We have a problem".
She went on to say that somebody had brought a VERY invasive plant, and as Master Gardeners we really can not let them be propagated. I was not aware that somebody had brought it, at first I was not even aware of how invasive it was. I had heard of it, but was not totally familiar with it.
I am now.
The plant was Sapium sebiferum, also know as the Chinese Tallow Tree, and the Popcorn Tree. You will also find it still listed as Triadica sebifera, but the Sapium sebiferum is the proper name.
The Popcorn tree is native to China and Japan where it has been cultivated for its useful seeds and as an ornamental for more than a thousand years. It is said that Benjamin Franklin introduced it into the United States in 1776 for use of its waxy tallow in soaps and candles.
It is a deciduous tree (loses its leaves) that may reach 60 feet in height. The bark is a light gray. It has heart-shaped leaves with a pointed tip.

Slender, drooping spikes up to 8 inches long appear from April to June. In Fall the leaves turn brilliant shades of scarlet, orange, yellow and maroon.

Popcorn Trees can invade a variety of habitats ranging from swampy to saline waters, and from full sun to shade situations. It is often found growing along roadsides, coastal areas, and streams. Larger specimens can produce up to 100,000 seeds that may be eaten and dispersed by birds, facilitating the spread. Native species are crowded out once the Chinese Tallow becomes established. The leaves and fruit are toxic to cattle and cause nausea and vomiting in humans.
It tolerates almost any soil and can grow 5 feet tall in its first year. They are considered moderately drought tolerant. However, It was planted as a street tree in California where it apparently has not yet become invasive, perhaps because of insufficient rainfall.
They have become so invasive, first off, being that they are a native of Eastern Asia, which is the same latitudes as the Southeastern U.S. they love the growing conditions here, but primarily because of the seeds that are readily eaten and dispersed by birds. The seeds also float and can be carried easily by rivers, streams, and stormwater runoff to new destinations and virtually all of them germinate somewhere. The seeds are in a fruit that are 3 lobed, brown capsules, 1/2 inch in diameter, when mature the outer part splits revealing 3 white waxy seeds that resemble popcorn, hence its common name. They mature in late Summer to early Fall.

Photo Courtesy of University of Georgia

If all of this is not bad enough, The leaves produce allelopathic chemicals that change soil content and therefore makes the area uninhabitable to native species.
It has gotten so bad that, the State of Florida lists the Popcorn Tree or Chinese Tallow as a noxious weed and prohibits its introduction, movement or release.
To kill these things, cut the tree down and immediately paint the stump with a triclopyr herbicide such as Brush-B-Gon, Garlon, Pathfinder, Chopper or something like Round-up brush killer. Make sure you follow the label directions or get a certified professional to apply these. Results also can be obtained by spraying the bark in a 6 inch wide band all around the base of the trunk with one of the triclopyr herbicides. I don't usually suggest such harsh treatment because of the danger it can pose to the homeowner and the landscape, BUT, tests of simply cutting down the trees resulted in extensive root and stump sprouting. Before applying any herbicide, read the label!! I can not emphasize this enough.
This is nasty tree. Yes, it has pretty Fall foliage and can be used for some good shade. Tree species recommended that are similar in size to Chinese Tallow include Maples (Acer spp.) and Crape Myrtles (Lagerstroemia spp.). Might I also suggest to use an Eastern Redbud (Cercis canadensis), or a Red Mulberry (Morus rubra) instead. At least the Red Mulberry will give you something good to eat!
Happy Growing!

Sunday, September 18, 2011

Mosquito be gone

I was actually searching for a good blog article today when I got a couple of very nice e-mails from a woman who just found my blog. She lives very close by and was wondering about growing Lemon Eucalyptus to rid her yard of mosquitoes.
I am going to use this as an opportunity to help her and others with this biting problem.
I will start with the Corymbia citriodora, or Lemon Eucalyptus, also known as Lemon Scented Gum, and Blue Spotted Gum. There are some sites that still refer to it as Eucalyptus citriodora.

Corymbia citriodora

The U.S. Centers for Disease Prevention and Control has now approved oil of Lemon Eucalyptus, also known as p-menthane 3,8-diol or PMD, as an effective mosquito repellent.
This evergreen tree is native to Queensland, Australia. In nature the trees will reach anywhere from 75-100 ft. Even though it gets very big in nature, it's size is easily controlled with selective pruning. It will even flourish in a large container this way. The trees are hardy in USDA zones 9-11, so a greenhouse will be needed for colder climates.
Citriodora needs full sun with a well-drained soil. These trees grow in very nutrient poor soils and fertilizer is not needed. They are propagated by seed in the Spring.
The oil of the lemon eucalyptus is a natural, plant-based repellent oil that is prepared from the leaves. It is commercially compared to Citronella.
You would think that Citronella would be made from the Citronella Tree (Citronella mucronata) which is native to Chile.

Citronella mucronata

It is an evergreen tree, which can grow up to about 30 feet tall with a diameter of about 3 feet. The bark is dark gray and rough.
In its native habitat, It grows in areas of high humidity and constant rain. It is mostly found on steep slopes, and usually in shaded places where there is protection from direct sunlight. The Citronella Tree can tolerate low temperatures down to about 18 degrees and can even survive an occasional snow.
Well, this is not the source of "true" Citronella oil either.
There is another plant that has a deceptive name of Citronella Plant. It is a geranium plant marketed as "Pelargonium citrosum".

Pelargonium citrosum

The marketing suggests that if you plant this around your yard, it will chase away mosquitoes. Not only is the plant ineffective in repelling mosquitoes, the mosquitoes were seen landing and resting on the plant on a regular basis. It does have a very nice lemony scent.
Okay, I have held you in suspense long enough.....if you want to grow the "true" Citronella oil plant, look for Cymbopogon nardus.

Cymbopogon nardus

It is a coarse, clump-forming tropical grass that can grow 5-6 ft tall. Citronella grass is native to southeast Asia and grown commercially in Sri Lanka, India, Burma, Indonesia and Java. It is widely naturalized in tropical Asia and grown as an ornamental in South Florida and southern California.
It does best in full sun. It is a perennial (comes back every year) in USDA zones 10-12. It needs a long, warm growing season, and may not survive cool, damp Winters. Being that it does not spread by runners, as some grasses do, but is a clumping grass, growing it in a container is an option. Propagation is by dividing the clumps. It is not picky about its soil, it will grow pretty much in anything you give it.
As I mentioned, Citronella grass is the source of the commercial Citronella oil. The oil from this grass can be mixed with other vegetable oils and used in massages or rubbed on the skin for an insect repellent. If you are one of those that like to burn Citronella candles or incense, I have bad news for you. Studies have shown that to keep mosquitoes away, you would have to burn so many candles that the smoke would be almost intolerable.
It is also been reported that Citronella oil repels cats.
I hope this helps clear up some of the confusion about the different Citronella plants out there. Some will disagree with what I have said, they will swear up and down that the geranium works or that they burn a Citronella candle and they never see a mosquito. This may be true. It is also possible that there wasn't any mosquitoes around or that they found somebody better tasting!
Happy Growing!

Sunday, September 11, 2011

A Rose by any other name.....

...may not even be a Rose!
This is where the common names of plants can really get you in trouble. The past couple of weeks, I have been asked about some of the tall bushes that have all kinds of flowers on them. What are they? Is the most common question, followed by: Are they hard to grow? and Where do you get them?
The plant in question here is the Rose of Sharon, If you lived in Britain or Australia they would think you are talking about Hypericum calycinum, which is an evergreen flowering shrub native to Southeast Europe and Southwest Asia. We know it here as St. John's Wort.
It looks like this:

I know there are a bunch of people that just had a cow! That is NOT a Rose of Sharon!! It is if you live in Australia or Britain.
Here in the good old USA, the Rose of Sharon (Hibiscus syriacus) looks like this:

THIS is the plant everybody has been asking me about.
See how common names can get very confusing? Depending on who you ask, or where they are from may determine what kind of plant you get. That is why I try to talk in botanical names whenever possible. It also goes by other common names such as: Althea Rose, Syrian Rose, and Shrubby Althea. There are many other plants out there with an identity crisis, but I digress.
The Rose of Sharon (Hibiscus syriacus) is a deciduous (loses its leaves) flowering shrub native to East Asia. It is the national flower of South Korea and was mentioned in an article produced 1,400 years ago. So this flower has been around for quite sometime.
It is an upright plant that produces colorful, cup-shaped flowers in Summer and Fall. They can range from 2-4 inches across.
The colors are almost infinite in number, including blue, pink, red, lavender, purple, white, and many of these in combinations depending on the variety.

Some have flowers that strongly resemble the familiar hibiscus; as you can see above. There are others that have small double petals that appear rose-like or are almost like a peony.

The Rose of Sharon grows well in USDA hardiness zones 5B through 9A. It will attain a pretty decent size. Averaging from 8-10 feet tall and 6-8 feet wide. It is best to grow Rose of Sharon in full sun, it can tolerate up to part shade. It prefers moist, well drained soil that contains lots of organic matter, though, it is able to tolerate a wide variety of soil and drought conditions. The plant may survive extreme conditions, but the buds may drop off if the plant is watered too much or too little, or if too much fertilizer is applied. When it comes to feeding, fertilize your Rose of Sharon just before the flowering period. Apply a balanced granular fertilizer according to the package directions.
If you want bigger blooms, in the Winter or early Spring, prune off last seasons growth. It will flower on the new growth. This is also a good time to be propagating them. It is easily propagated by hardwood cuttings that are 4 - 6 inches long taken in the Winter and planted about 1-1.5 inches deep in a mixture of coarse sand and peat moss. Stick the cut ends in some rooting hormone and keep these warm, moist and humid. You can also use softwood cuttings in the Spring, using the same method as above.
Aphids and Spider Mites can be a real nuisance, However, one of the biggest problems that Rose of Sharon faces is the Japanese Beetle.

If you have leaves that look like this, then you have a Japanese Beetle problem.

My mother just cringed when she saw these pictures, she is very accustomed to this problem. Her favorite way to deal with it, walk around the yard with a bucket of soapy water and drown the little varmints.
You can also use a product called Milky Spore. It is an organic approach to ridding your yard of the grubs that turn into the beetles. One word of caution, you will need to get pretty much your entire neighborhood involved in this. Just because your yard is protected, they live next door, and the pupating beetles will fly over for a feast.
Diseases that you need to be aware of include leaf spot, blight, and cankers. These can be controlled with fungicides or proper placement of plants. Make sure that there is good air circulation between them and they are planted in the proper place.
As you can imagine, with a history as long as this beautiful flower, there are some interesting tidbits surrounding it, especially in the world of music.
"Rose of Sharon" is a song by Robert Hunter (From the Grateful Dead) which he released on his solo album Tiger Rose.
"Rose of Sharon" is a song sung by Joan Baez on the album Day After Tomorrow.
Judah Robertson has an album entitled "Rose of Sharon".
The Rose of Sharon is referenced in the Bob Dylan song "Caribbean Wind."
Rose of Sharon is also the official flower of Phi Beta Chi, a national Lutheran-based Greek social letter sorority.
There are many, many other references to the Rose of Sharon from Biblical mentions to Novels and Poetry. I just find the flower very pretty and I hope you do too.
Just remember, a Rose by any other name...might just be something completely different!
Happy Growing!