A great new gardenia cultivar called Frostproof (Gardenia jasminoides Frostproof) will be the first of the spring Louisiana Super Plant selections to be announced by the LSU AgCenter.
The Louisiana Super Plant program is an educational and marketing campaign that highlights tough and beautiful plants that perform well in Louisiana landscapes.
Gardenias are one of those plants we consider one of our Southern heritage plants.
Although they are native to the Far East (like crape myrtles, azaleas, camellias and many other Southern heritage plants), we have grown them in the South for so many generations that we feel as though they are part of our culture and gardening tradition.
Fragrance is one of the things that attract gardeners to this shrub. Gardenias produce single or double white flowers that emit a powerful scent.
The fragrance of gardenias on the languid breezes of an early summer evening is about as Southern as it gets. Some find the strong aroma a little overwhelming, but most gardeners will gladly bury their nose in a flower.
The lustrous dark green foliage is evergreen and attractive year-round.
At times, generally from early winter to late spring, older leaves will turn bright yellow and drop off. This is normal, and up to one-third of the leaves might drop -- but there's no need for concern when this happens.
The shrubs might look a little thin after leaf drop but will fill back in with new growth in the spring.
Get the pH right
Gardenias are acid-loving shrubs that prefer a soil pH of 5.5 to 6.5.
Soils in much of the New Orleans area aren't acid enough or are even slightly alkaline, particularly in the alluvial soils of the south shore.
When grown in soils not acid enough, gardenias have trouble absorbing the iron they need from the soil (all plants need iron to be healthy). This leads to a condition called iron chlorosis.
It will appear primarily in the newer leaves. Typically, the veins of the leaves will be green, while tissue between the veins is yellow or yellowish green.
In some cases, the entire plant might take on a yellowish cast. This looks different from old-leaf drop and shouldn't be confused with it.
If you have gardenias in your landscape that are iron-deficient, apply an iron fertilizer to provide available iron and a soil acidifier to lower the pH of the soil in the bed.
Although acid-loving plants like azaleas and camellias do well in the soils of the south shore, gardenias aren't as adaptable.
If you are preparing a bed for gardenias and the pH of your soil is above 7, you should add sulfur, copperas or other soil acidifying agents to lower the pH.
Make your bed
Other than attention to the pH, the bed preparation is typical.
Incorporate a 2- to 4-inch layer of organic matter, such as compost, composted manure or soil conditioner. Peat moss may also be used, and since it is acidic, it's especially good for preparing beds for acid-loving plants.
When finished, beds should be slightly raised, about 6 to 8 inches above the lawn. This will help provide good drainage that gardenias and most other shrubs prefer.
When it comes to pruning, it should be done immediately after early summer flowering finishes, around June or early July.
This is because gardenias set their flower buds in late July to early August and carry them over the winter to bloom in May. There are flower buds on your gardenias now that will open in a couple of months.
As popular as they are, gardenias can sometimes be fussy. This is particularly true of the dwarf types.
They commonly have problems with root rot and are one of the few shrubs that can be seriously damaged by root nematodes. Put gardenias in a spot they like, and they are reliable and easy, but failure isn't uncommon.
That's why we are always keeping a look-out for tough, reliable gardenia cultivars, and Frostproof looks like it will be one of the best.
The Frostproof gardenia
The Frostproof gardenia was chosen for the Louisiana Super Plants program for a variety of reasons.
This evergreen shrub produces fragrant, double, velvety white flowers heavily in May, then sporadically through the summer. This cultivar is known for its prolific production of flowers.
Frostproof, as its name implies, is cold-hardier than other gardenias, although this isn't much of a factor in Louisiana. Still, this gardenia can be counted on to hold up through even unusually cold north Louisiana winters.
It also has proven to be tough, adaptable and reliable in a wide variety of landscape situations.
Gardenia shrubs can grow to be quite large, as big as 6 to 8 feet tall and 6 to 8 feet wide. Frostproof, which grows about 5 feet tall and 4 feet wide, is considered a compact gardenia that will fit in well where a smaller shrub is needed.
The leaves are somewhat smaller than most other gardenia cultivars, giving the plant an attractive, medium-to-fine texture.
The Super Plants Program
Louisiana Super Plants have a proven track record having gone through several years of university evaluations or years of observations by industry professionals.
Home gardeners and professional horticulturists should consider using Louisiana Super Plants when deciding what to plant. Louisiana Super Plants are "university tested and industry approved."
There are three parts to the Louisiana Super Plants program. The first is identifying outstanding plants, and the second is making sure the plants are available at retail nurseries and garden centers.
The third is getting the word out to Louisiana gardeners about these great plants. Look for information on Louisiana Super Plants in newsletters, magazines, newspapers, TV segments, radio and on the Internet at www.lsuagcenter.com/SuperPlants.
In addition, when you visit your local nurseries, look for signs showing which plants are the Louisiana Super Plants selections.
Later this spring, other Louisiana Super Plant selections will be announced, including two excellent warm-season bedding plants: a Serena Series angelonia and Butterfly Series pentas.
Shoal Creek vitex, a small summer-flowering tree that also is grown as a large shrub, also will be highlighted.
More on them later.
DAN GILL'S MAILBOX
I have read with great interest your recent recommendations about choosing plants for landscaping.
So many factors: cold and heat, moisture requirements, mature size, etc.
I have always had the most problem correctly selecting plants based on sunlight received. Too often a plant has performed poorly because what I thought was "partial sun" turned out to be too shady for good growth and blooming.
What is the best way to determine the light exposure? How can I tell how many hours of sun a particular part of my garden receives? How do I handle the changes that come with the seasons? What about sun during the winter when the trees drop their leaves and plants beneath the trees receive more sun temporarily? Is it worth investing in a meter to measure the sun exposure?
I am determined to select only plants that won't freeze, can tolerate summer heat, aren't too finicky about water, don't need constant pruning, are bug/disease resistant and are interesting or pretty!
That's a tall order. If I can get the sun issue figured out, then I guess I can move on to all the other variables.
I'm so glad you asked.
Gardeners and professionals alike often use the terms shade, part shade, part sun and full sun without really understanding what specifically is meant. Generally, a light meter isn't needed to evaluate light conditions in your landscape, but it does take time and study.
You can only tell how many hours an area of your landscape receives by regular observation. Here are the basic definitions for the terms we commonly use to describe the light conditions various plants prefer:
Shade: about two hours of direct sun in the morning or dappled light through the day; a northern exposure.
Part shade: about four hours of direct morning sun; an eastern exposure.
Part sun: about four to six hours of direct sun midday to sundown, afternoon sun; a western exposure.
Full sun: about eight hours or more of direct sun; a southern exposure.
A full shade location receives little or no direct sun, and this isn't common in typical landscapes. Only the most shade-loving plants will grow in full shade, such as cast iron plant or ferns.
Light does change with the seasons, so you will need to observe frequently and assess the light conditions around your landscape through the year.
When dealing with a spot where the light changes radically when deciduous trees drop their leaves in winter, here's how you figure it: Use plants under the trees (or in the shaded area) that will receive the light exposure they prefer when they are in active growth.
During the summer, the area will be shady, so, plants that are awake and in growth there in the summer must enjoy the shade.
During the winter when these plants are dormant -- the temperatures are cool, the days are short and the sunlight is weaker -- shade-loving plants will easily tolerate the sun when the trees drop their leaves.
On the other hand, spring-flowering bulbs such as daffodils and snowflakes need a sunny spot to grow and bloom well -- but you can also plant them under the deciduous trees. That's because they are in active growth during the winter. When they need the sun, the deciduous trees have dropped their leaves, and the bulbs will get plenty of sun. During the summer when the trees leaf out and it is shady, the bulbs are dormant and they don't mind.
Make sure you are looking in references written for Louisiana or the Gulf South when looking at possible plant choices.
Also, when selecting plants in the nursery, tell the person on the staff helping you about the plant characteristics you seek, just as you described them in your e-mail to me.
Can the azaleas be fertilized before blooming?
Yes they can.
However, most gardeners wait.
Fertilization can encourage azaleas to send out their new growth while they still are blooming. While this isn't a problem for the plant, it's disappointing to see the flowers covered partially by the new growth.
Some azaleas will do this anyway, but there's no use encouraging them. So, most of us wait for our azaleas to finish blooming before fertilizing them.
Dan Gill is extension horticulturist with the LSU Ag Center.
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