1954
publication by Louisiana Cooperative Extension Service
You will be interested in planting Louisiana native irises in your home
garden. You can grow them with little difficulty. Once you get started, it will be a
fascinating experience because of their color, variety and beauty of flowers.
This popular wild flower ranges from white through all the lavenders,
blues and violet to deepest purple. There are also color values of pink, rose, red, bronze
and yellow, as well as bi-tones, bi-colors and flecked specimens.
Under best growing conditions in their native habitat, some flower
stalks over 6 feet tall have been found and some as low as 4 inches.
The blooming season starts in March on the Gulf Coast and moves
northward with the season. The low areas of Louisiana along the edges of its numerous
streams have been naturally planted with the wide distribution of the floating native iris
seeds.
As garden flowers, wild irises do well under a wide variety of soil and
garden conditions and landscapes. They will thrive on highlands and on lowlands. Bog
culture is ideal, if the landscape permits. The shallow edge of a lake or pond is a most
natural spot for Louisiana irises.
National Recognition
Louisiana native irises have gained national acclaim and are becoming
more popular with amateur collectors and gardeners. Nurseries and gardeners are now
propagating this rainbow flower for distribution.
DISTRIBUTION
Native irises of various types are widely distributed in Louisiana but
are more numerous in the Gulf Coast area.
"The Iris Center of the Universe" was the phrase coined by
the late Dr. John K. Small, authority on plant life, to describe the rich, wild iris
fields of southern Louisiana. Dr. Small, as curator of the New York Botanical Gardens, was
one of the first to describe these fields and to call attention to their magnitude, to the
great variety of the flowers and to the unusual size of the plants.
The vicinities of New Orleans, Thibodaux, Houma, Morgan City,
Prairieville and Abbeville are melting pots of rainbow colors. Here are found the hybrids
resulting from natural crosses of two or more of the following three species: giant blue
(giganticaerulea), rust-red (fulva), and dwarf blue (foliosa). These hybrids usually occur
where many different types of irises have grown for some time close together in one small
area.
The Abbeville fields, where the three species are found, are located
near a converging point of several streams. Because of the masses of rainbow colors, the
area is referred to locally by iris collectors as the "Iris Heaven."
SPECIES AND TYPES OF NATIVE IRISES
In discussing types of native irises, the author proposes to give only
a general description of five types found in Louisiana. He makes no attempt at botanical
classification. Much research needs to be done by botanists and geneticists on systematic
classification of native irises.
Rust-red (fulva)
The small, numerous blooms of rust-red shades are on erect stems about
30 inches in height. Both petals and sepals droop and have no signal patch. Rust-red
occurs in color values of crimson, pink and even clear yellow. It grows abundantly in the
lowlands of the Mississippi and Red River valleys, being more numerous and larger near the
Gulf Coast. This iris was first described in 1812. It occurs naturally as far north as
Missouri and Ohio.
Abbeville Types
The Abbeville Red or "Super" fulva is found in southwest
Louisiana near Abbeville. These giant reds are in a class all their own. The color range
is from red to yellow and brown to deep purple. The wide, overlapping petals and sepals
are sometimes marked with a long crest or signal patch. Sometimes they are devoid of any
signal markings. Most blooms have a wonderful substance and may be of crepe-like texture
and a velvety sheen. The style arms are short. The foliage is broader and the rhizomes are
larger than those of the regular fulva.
Dwarf (foliosa, including Flexicaulis, Brevipes and Mississipiensis)
The flower is medium-size. It has much substance and a color range from
blue to white. Blooms usually occur low in the foliage on zigzag or fairly straight stems.
Plants and rhizomes are much smaller than those of other forms. This type blooms later and
grows usually in shadier places than others. It is found growing naturally in the prairie
and bluff areas of Louisiana. The Dwarf occurs from Vermilion Parish to West Carroll
Parish and east of the Mississippi River from Ascension to West Feliciana parishes.
Giant blue (giganticaerulea)
The large, recurving flower parts range in color from blue and purple
to white. Flowers with vertical petals (standards) and horizontal sepals (falls) are borne
at different levels on tall, erect stalks. These Giant Blues are found along the Gulf
Coast of Louisiana on the edges of bays fed by fresh water and bordering on salt water
marshes.
Pine Flat Types (virginica, including Versicolor, Shrevei and
Carolina)
The medium-size flowers range in color from deep blue to white, with
heavily-veined, fragrant blossoms on lateral, branching, slender stems. The dark green
foliage has a decided midrib. This characteristic is not found in any other Louisiana
native iris. Pine Flat Types are not known to cross-pollinize with other forms of
Louisiana native irises. Natural habitats of this type are in the low, pine flat areas of
southeast and western Louisiana from Calcasieu to Caddo parishes. East of the Mississippi
River they occur abundantly north of lakes Pontchartrain and Marepas. The soils in these
areas are more acid than in the alluvial and bluff areas where other Louisiana irises grow
naturally.
HORTICULTURAL VARIETIES AND HYBRIDS
Hybrids found in the wild, as well as those produced in the garden by
hybridizers, number in the thousands. As these hybrids make good, they may be given a
variety name. Some of the best irises have no name, while others have several names. Many
of the named hybrids have been registered and the descriptions recorded with the American
Iris Society.
The group of plants collectively classed as "Louisiana
Irises" is composed of three principal species and their hybrids. The species are I.
fulva, the red or flame-colored iris of the Lower Mississippi Valley; I. giganticaerulea,
the tall blue of the Lower Gulf Coast; and I. foliosa, the little blue-to-lavender dwarf
of the bluff or terrace lands.
Iris virginica is also native to Louisiana but it grows in regions
outside of the State and does not hybridize with the other species. It is largely a native
of the poorer pine flatlands.
More information on varieties or hybrids can be obtained from the
publications listed at the end of this article.
PROPAGATION
Growers of irises are interested in increasing the quantity of their
best varieties. There are two practical methods of perpetuating or increasing iris
stock--by the vegetative process and by seed propagation.
- Vegetative Reproduction
Iris plants increased by this method will produce plants identical
to the variety from which they were propagated. This is the only sure way of maintaining
an established strain of iris without variation of bloom and plant. Propagation by seed
may vary greatly from the parent plant, unless it is a pure strain.
Vegetative increase may be obtained by (1) rhizome separation, (2)
rhizome cuttings and (3) flower stalk off-shoots. The ideal time of year for success with
the first two practices is after the dormant season in later summer and early fall (August
to October in Louisiana). The other good time is in early spring at blooming season (March
to May in Louisiana).
The advantages of spring propagation are that it is easier to identify
plants when in bloom and there is less rotting of the rhizomes. However, planting may be
done at any season of the year.
Rhizome Separation
Under
natural conditions, single rhizomes usually multiply two- or
three-fold in a year but have been known to multiply 21-fold, spreading
radially. When a
single rhizome forms a bloom stalk, it usually produces also two side shoots.
These shoots
from new rhizomes and continue the process of natural increase. However,
the original
rhizome usually deteriorates as increased growth takes place. Similar multiplication
will
occur naturally under good garden conditions without mechanical separation
but the process
can be speeded by mans help.
One
clone from a two-year-old seedling plant in the writers
garden developed radially into 21 side rhizomes. This is unusual. But imagine
how much
increase could be obtained in several years, if a plant like this could
be separated and
given more room to develop. Most plants will produce an average of three
to six side
rhizomes the first year or two. By this method, they can be increased to
as many as 15 to
20 plants in one year.
Mechanical separation is easily done by breaking off the side rhizome
from the main one and transplanting it immediately. The main rhizome with the bloom stalk
is then likely to spout out more shoots from the dormant buds at the leaf scars. The
ring-like scars on the rhizomes indicate where the leaves were attached. At each scar
there is a bud or potential new plant .
Rhizome Cuttings
Cuttings of 2- to 3-inch sections of the rhizome should be planted
in propagating media, such as vermiculite or well-rotted leaf mold, peat moss and sand or
sphagnum. Avoid planting cuttings too deep. Just barely cover and keep them moist in a
cool, shady place. Be careful not to over-water or soak, since this may cause them to rot.
As each new shoot reaches 4 to 6 inches in height, carefully remove the
rhizome cutting, new shoots and all new roots formed in the growth medium and place them
in a bucket of water until planted. With a sharp knife, separate the new plant with all
its new roots from the rhizome section. A portion of the rhizome may be sliced off in this
process. The new plant should then be transplanted in a well-prepared, fertile plant bed
and shaded until well grown out. The rhizome cutting should be replanted in rooting media
to develop additional plants. The process can be repeated until all the buds on the
cutting have been developed.
Flower Stalk Off-shoots
This method of propagation may supplement the others, if a maximum
increase of a desirable, rate variety is wanted. The off-shoots on the stalk are similar
to those of the day lily. However, the flower stalk buds at the leaf nodes must be
stimulated into growth. Do this by cutting the stalk while it is still green, after
blooming, but before the seed pods form. Then place the flower stem in a container of
water so that the water line is slightly above the base of the leaf node and keep it in
the shade.
Another method is to place the flower stalk almost horizontal in a sand
propagating box. When the off-shoot an dits roots have developed, remove the off-shoot
from the flower stem and transplant it.
- SEED REPRODUCTION
Seed pods will develop on most wild irises. If pollinated, each pod
will produce from several to about 60 cork-like seeds. This method of increase is very
important to iris hybridizers in developing new forms and colors but is slow. All the
seeds in a pod may not germinate the first year.
Gardeners who desire large quantities of plants for mass plantings may
be interested in using seeds also, if trueness to variety is not important. Most Louisiana
irises are hybrids and their seedlings will vary in color, size and form.
If iris seeds are left on the stalk to mature fully and harden, they
germinate very slowly. The fully matured, late harvested, dried-out seeds will go into
what is known as a "rest period" and it may take several years for all of them
to spout. However, you can hasten germination of iris seed by harvesting them when the
seed pod is still partially green. Planting at harvest time (June and July in Louisiana)
will produce a higher percentage of seedlings by fall and early spring.
Use of Flats
Do not plant seed in garden beds, because weeds will choke the plants
and heavy rains may wash the seeds away. A better plan is to plant in flats, cans or other
containers partially filled with a good propagating medium, such as vermiculite or leaf
mold and sand.
Good drainage is important. This is best accomplished by making small
holes in the base of the cans or other containers used.
Plant seeds approximately ½ inch deep, water thoroughly and place in a
cool, shady spot. By all means, protect seed from rats. Keep seed moist until all are
sprouted but do not over water, since this will cause the seed to rot. As the seedlings
emerge to 5 or 6 inches in height, lift them carefully, avoiding damage to the tender, new
roots, and transplant them in a well-prepared, rich soil that is high in organic matter.
Space plants about a foot apart in the beds.
Transplanting
The best seasons of the year for transplanting wild irises are fall and
spring, although it can be done at any time. During hot weather, wild irises do not grow
and are more susceptible to rot when rhizomes are exposed to direct, hot summer sun. Most
of their growth occurs during rather cool weather. Getting irises transplanted and
established in the garden by late summer or early fall increases chances for a bloom crop
the next spring.
In collecting plants in the wild or digging them in the garden, you may
use either whole fans (large blooming stalk rhizomes with side shoots) or small
single-side rhizomes about 3 to 4 inches long. It is best to do this during the blooming
season, because of identification. If identity is to be kept, attach labels at digging
time.
If plants are to be shipped a long distance, or held over for some time
after digging, you may pack them in moisture-retentive material, such as damp sphagnum or
vermiculite. The stored food in the rhizome keeps the rhizome from deteriorating very
fast.
Setting
Set the plants about a foot apart in the garden. Shallow planting is
best, with the top of the rhizome level with the top of the soil. Then mulch the beds with
an inches of well-rotted organic matter, such as plant leaves, peat moss, sugar cane
bagasse, cotton gin mote, rice hulls or rotted sawdust. Water thoroughly and repeat
occasionally, if dry weather prevails. After transplanting the young seedlings, which are
small and delicate, give them special care until they become well established.
Creating New Irises
Amateur hybridizers among iris growers are increasing in number by
leaps and bounds. They are creating new irises by cross-pollinating and by
self-pollinating desirable flower varieties. This is easy to do and the number of possible
new varieties is endless. Once you get started, it is just as much fun as walking the
swamps to find new natural hybrids. Collecting in the wild as a means of getting new
floricultural varieties will require a lot of time and travel. Buying from nurseries may
be costly.
When you make crosses and produce seedlings of your own, the pleasure
in gardening increases. Waiting for your own seedlings to bloom is like waiting to open a
Christmas package. If the bloom and plant are "super" and make good, then the
thrill approaches that of parental pride.
Method of Hybridizing
The technique of hybridizing is very simple. A little practice and
experience will start you on the way to iris breeding.
Just before the fully-grown flower bud on the mother stalk opens, it
should be carefully forced open. This is done by firmly holding the base of the flower
with the left hand, lightly pinching the tip of the bud with the right hand and twisting
it open. Remove the male parts, or stamens, immediately so as to avoid accidental
contamination. A pari of eyebrow tweezers is an ideal instrument for this. At this stage,
the stigma (female part) is highly receptive. It is a simple trick then to expose the
stigmatic surface by raising the claw and thoroughly dusting the exposed surface with
mature pollen which was removed from the desired male plant. To do this, simply rub a
well-opened stamen on the stigma and the flower is pollinated.
This completes the operation, except that the flower should be bagged
to prevent later contamination by insects or other natural agents. Some hybridizers just
break off the sepal instead of bagging the crossed bloom.
Identification
The next step is to tag, label and date the cross; example: fulva x
foliosa--3/24/49. The female or mother plant is always listed first. In the case of
self-pollinating a bloom, use the symbol X; example: Bayou Sunset X--3/24/49.
Typing the stalks to small stakes may keep them from bending to the
ground. This will prevent seed pod rot and make the seed less accessible to rats, which
relish iris seeds.
Inheritance
Plant breeding, of course, presents a problem of inheritance. All wild
irises possess the important hereditary factors of color, size, form, substance of flower,
disease resistance and other plant characteristics. However, you do not have to be a
professional geneticist to develop outstanding new irises. When you do develop a good
hybrid, it can be rapidly propagated vegetatively. It is important to have a healthy,
vigorous grower and a well-adapted individual.
Selecting desirable parent stock will, of course, be somewhat of a
problem until you have gained experience but you may be lucky, if you try.
SOIL PREPARATION, CULTIVATION
Soil and cultural requirements of the native irises are the opposite of
those of the bearded iris. Natives thrive best in slightly acid or sour soil, with
abundant moisture. The bearded do their best in alkaline or sweet soil and with very good
drainage. Highland, lowland or even bog conditions are satisfactory for the natives.
In locating plant beds in your landscape plan, remember that wild
irises require moisture and humus. Most varieties thrive and bloom best in full sun to
semi-shade. Some of the foliosa types do well in partial shade. Necessary protection from
the hot summer sun should be provided by mulching. Good seedbed preparation prior to
planting, then mulching over the rhizome and around the plants immediately after planting
will reduce the need for cultivation.
Deep Breaking
Deep plowing or spading, followed with thorough harrowing or raking, is
essential to good soil preparation. Deep preparation improves the physical condition of
the soil, increases its ability to absorb and retain moisture, makes the natural and
supplementary supplies of plant food more readily available and helps to destroy
unsightly, harmful weeds.
Very little cultivating will be needed, except to control weeds. A
small, narrow spring-tooth garden tool is ideal for cultivating. If a hoe is used to
cultivate in the fall and spring, take care not to cut the shallow rhizome. Under no
circumstance, should you use a hoe in the iris bed during midsummer when the shallow
dormant rhizomes are so easily disturbed.
Thin plantings of summer, shade-producing legume plants, such as
soybeans or crotelaria, may be made after the iris-blooming season. This will protect
plants form sun, conserve moisture an control weeds.
FERTILIZATION
Plenty of organic material, such as animal manures, compost or green
legume crops turned under with the soil, plus commercial fertilizer, is necessary for a
good iris bloom crop. Poultry yard manure is the most effective for irises.
The well-rotted organic material should be worked into the soil while
preparing the beds and also spread lightly over the rhizomes just after planting. Use at
least a good wheelbarrow load per 6 to 8 square feet.
Commercial Fertilizer
Supplemental plant food in the form of commercial fertilizer should be
used in several applications both in early fall, when roots start developing, and in very
early spring, about two months before blooming. A nitrogen fertilizer, such as nitrate of
soda, sulphate of ammonia or ammonium nitrate, is recommended for very early fall at the
rate of 1 pound per 100 square feet. This should be thinly spread between the plants.
A complete fertilizer (nitrogen, phosphorus and potash) applied in
January or February of about two months before the blooming season will increase your
chances for good quality and size of blooms. Any complete garden fertilizer available in
your local stores should be suitable. However, an 8-8-8, 6-12-6 or 5-10-5 is recommended.
Apply this mixture around the plants at the rate of 2 or 3 pounds per 100 square feet.
IRRIGATION
Water is essential for natural distribution of Louisiana irises, for
the establishment of young plants and for a good bloom season.
Moisture is most needed during fall when plants are getting established
and in early spring for about two months prior to blooming. This usually coincides with
the rainy seasons in Louisiana.
During these periods, if weather is too dry, it may be necessary to
irrigate thoroughly. One thorough soaking of the iris beds is better than an occasional,
light sprinkling. Soils high in organic matter store more moisture for dry seasons. This
is why irises do so well in a fertile soil where a lot of humus and a liberal mulch have
been added.
Planting the irises in depressed beds will facilitate irrigation. This
is even more important in the drier hill sections of Louisiana. Bog culture, when the
landscape plan permits, will help to solve this problem.
DISEASES AND PESTS
Louisiana irises have few pests or enemies. Some of them follow.
Rot or Mustard Seed Fungus
It
occurs in the soil and may attack susceptible iris plants at the
ground under warm, wet soil conditions. A fungicide, such as Terraclor, applied
to the
soil as a dust or in a solution may help to reduce the damage. An effective
way to control
this soil fungus, if it becomes a serious problem, is to move the irises
to another
location temporarily and treat the soil with Terraclor. When the disease
appears, apply
the fungicide to the soil at the rate of 4 oz. of Terraclor per 100 square
feet. Be sure
to thoroughly mix the fungicide with 4 to 6 inches of the top soil and then
replant.
Remove the dead foliage to admit sunlight to the base of the clumps.
Rust
Some of the earlier blooming varieties are susceptible to this disease.
You may have to discard the most susceptible varieties. Removal and burning of all the
diseased leaves as soon as they appear will help to control rust. A spray of Fermate or of
Zineb may also check the disease. Use these fungicides at the rate of 1/4 pound to 10
gallons of water and spray the leaves when the rust spot first appears.
Thrips
This minute insect sucks the sap from the iris bloom. When it occurs in
large numbers, the blooms wilt and discolor. Control by spraying or dusting with 5% DDT
when the insect first appears. Additional applications may be necessary.
Orioles
If orioles fly in at iris blooming time, they are likely to go for the
nectar in the flowers and tear them up. How to stop them is a problem.
Sun Scald
After the blooming season, when irises go into dormancy and the dead
leaves are removed, sun scald often does a lot of damage to the exposed rhizomes. This may
cause rot. The damage can be easily corrected by covering the rhizomes with mulching
material or soil.
FLOWER SHOWS
Preparation of Native Irises for Exhibition
(1) Three or four days before the show, go over the garden and decide
what you will exhibit. (2) Label each bloom stalk. (3) Wrap each bud loosely in wax or
cellophane paper and fasten the wrapping securely with a pin or paper clip. This is done
to prevent damage by orioles or insects and to prevent breakage in transporting. (4) In
late afternoon before the show, cut the stalks 3 inches from the ground. Place the stalks
in a container of water but do not let the water cover the buds. Leave in a cool, shady
place for at least 12 hours to condition. (5) Remove the stalks from the water and place
them in a large, flat cardboard box for transporting to the show. They may be re-soaked,
prior to exhibiting, if time permits.
Upon arrival at the show, get entry tags and tie them on the stalks.
Place each stalk in the container of water where it is to be shown. Then remove paper
covering from buds and allow them to unfurl.
OTHER READING
You Will Be Interested in . . .
Arceneaux, George--Breeding Louisiana Iris, Home Gardening,
pages 92-93, April, 1947
Dorman, Caroline--The New Irises of Louisiana, The American Home,
11:6, May, 1934
Dorman, Caroline--Those Fabulous Louisiana Irises (special A. I. S.
bulletin), November, 1947
Dorman, Caroline--Louisiana Iris Journal--1949, Home Gardening,
New Orleans, October, 1949
Dorman, Caroline --Flowers Native to the Deep South, 1958
Nelson, Ira S. --A Review of Louisiana Irises, The National
Horticultural Magazine, pages 183-192, October, 1944
Reed, George M. Excerpt from A. I. S. Bulletin No. 106, July, 1947
Small,
John K. 1931 Manual of the Southeastern Flora, New
York Botanical Garden
Viosca, Percy, Jr. --The Irises of Southeastern Louisiana, April, 1935
(Reprint from A. I. S. bulletin)
Other special articles on Louisiana Irises are to be found in bulletins
of the Society for Louisiana Irises, Lafayette, Louisiana, and bulletins of the American
Iris Society, Nashville, Tennessee.