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[ / / Central Science
NEMATOLOGY (BOTANY) CIRCULAR No. 15 FLA. DET. AGR. R SERVE.
APRIL 1976 1 4 8 Divi I1 OF PLANT INDUST Y

MILKWEED VINE, MORRENIA ODORATA--AN IDENTIFY NATION AlMAR 26 1987

K. R. LANGDON
University of Florida
MUCH HAS BEEN WRITTEN ABOUT THE MILKWEED VINE, MORRENIA OD RATA LINDL.- CONCERNS IT
SERIOUSNESS AS A PEST AND ATTEMPTS TO CONTROL IT (2,3,4,7,8,9,10,11). VERY LITTLE, HOWEVER,
IS READILY AVAILABLE AS AIDS IN IDENTIFYING THIS PLANT AND SEPARATING IT FROM OTHER SIMILAR
PLANTS. PHOTOS ARE AVAILABLE (2,3,9,10), BUT DETAILED DESCRIPTIONS ARE GENERALLY LACKING.
TAXONOMIC TREATMENTS COVERING MORRENIA ODORATA ARE SCARCE.
THE FIRST REPORT OF M. ODORATA ESTABLISHED IN FLORIDA WAS IN 1957 IN A GROVE IN ORLANDO
OWNED BY MR. D. J. NICHOLSON. THIS INFESTATION APPARENTLY CAME FROM SEED FROM AN ORNAMENTAL
PLANTING SOMEWHERE NEARBY, THOUGH THE ORIGINAL PLANT WAS NEVER FOUND. THIS INFESTATION
PLUS THE ORIGINAL PLANTING APPARENTLY FURNISHED SEED TO ESTABLISH MANY NEW INFESTATIONS AND
STARTED THE RAPID SPREAD OF THIS PEST.
M. ODORATA HAS SINCE SPREAD THROUGH CITRUS AREAS AS FAR SOUTH AS HIGHLANDS AND DE SOTO
COUNTIES, AND AS FAR NORTH AS MARION COUNTY. AT LEAST ONE ISOLATED PLANT WAS FOUND GROWING
NATURALLY AND SUBSEQUENTLY DESTROYED AT GAINESVILLE, ALACHUA COUNTY. IT IS NOT KNOWN HOW
FAR NORTH THIS PLANT WILL SURVIVE, BUT THE NORTHWARD SPREAD APPEARS TO HAVE SLOWED CONSIDERABLY.
IT SEEMS BEST ADAPTED TO CITRUS AREAS AND SO FAR HAS NOT BEEN A SERIOUS PROBLEM OUTSIDE
THESE AREAS.
WHEN THIS PLANT WAS FIRST FOUND AS A PEST, THE LATE PROFESSOR ERDMAN WEST TENTATIVELY
IDENTIFIED IT AS CYNANCHUM CUBENSE (GRISEB.) WOODSON. FLOWERS ARE NECESSARY TO SEPARATE
CYNANCHUM FROM MORRENIA. HE DID NOT HAVE FLOWERING MATERIAL AT THAT TIME, BUT WAS ABLE TO
CORRECT THE IDENTIFICATION TO MORRENIA ODORATA WHEN FLOWERS BECAME AVAILABLE. C. CUBENSE IN
FLORIDA IS RESTRICTED TO EXTREME SOUTHERN FLORIDA AND IS NOT A SERIOUS PEST.
MORRENIA ODORATA WAS DESCRIBED BY JOHN LINDLEY (5) IN 1838 FROM ARGENTINA. FOLLOWING
IS A DESCRIPTION PUBLISHED BY MORONG AND BRITTON (6) OF M. ODORATA COLLECTED IN PARAGUAY:
"A NOBLE VINE CLIMBING OVER SHRUBS AND TREES, FOUND IN THICKETS THROUGHOUT THE COUNTRY.
FLOWERS WHITE, VERY FRAGRANT. INSIDE OF THE COROLLA IS AN ERECT 5-LOBED CORONA. THE TRUNCATE
LOBES 2 TOOTHED, PROJECTING IN A FLAP OVER THE GYNOSTEGIUM. STEM AND LEAVES CANESCENT,
COPIOUSLY MILKY. LEAVES OPPOSITE, CORDATE OR HASTATE, ABRUPTLY CURVING INTO A LONG ACUTE
POINT, THE LARGEST 10 CM. IN LENGTH. FRUIT AN IMMENSE OVATE FOLLICLE, SOMETIMES 10 CM. LONG
AND 7 CM. BROAD AT THE BASE. SEEDS BLACK, SOMEWHAT ANGLED AND TUBERCULATE, LINEAR, 6 MM. LONG,
SURMOUNTED BY A SOFT WHITE SILKY COMA 4-5 CM. LONG. THIS PLANT IS OFTEN CULTIVATED IN GARDENS
AT ASUNCION, AND THE ABUNDANT COMA IS USED FOR MAKING PILLOWS, FOR WHICH PURPOSE IT IS WELL
FITTED, AS IT IS AS SOFT AS EIDER DOWN." BAILEY (1) MAKES THE FOLLOWING COMMENT: "ALLIED
TO CYNANCHUM, BUT DIFFERING IN ITS CONVEX 2-LOBED STIGMA (FLAT OR CONCAVE IN CYNANCHUM) AND THE
TUBULAR CORONA, WHICH IS LONGER THAN THE PISTILS, VILLOSE ON THE INSIDE, AND CONNIVING OVER
THE PISTILS. THE LVS. ARE OPPOSITE AND HASTATE. M. ODORATA, LINDL., IS MORE OR LESS IN CULT.,
AND IS LISTED IN S. CALIF. IT HAS WHITE VERY FRAGRANT FLS. IN DENSE CYMES IN THE AXILS; SEPALS
5, LINEAR; COROLLA ROTATE, THE LOBES WIDE-SPREADING AND ACUMINATE; CORONA TUBULAR, 5-LOBED.
ARGENTINA AND PARAGUAY. HAS MERIT FOR THE AGREEABLE VANILLA FRAGRANCE OF ITS INCONSPICUOUS FLS."
THE MOST READILY OBSERVED DIAGNOSTIC CHARACTERS OF M. ODORATA ARE THE LEAF SHAPES AND
THE GRAY-GREEN COLOR OF ITS FOLIAGE. THE LEAVES OF M. ODORATA ARE OPPOSITE ON LONG PETIOLES
AND ARE PRIMARILY OF TWO SHAPES (FIG. 1). LEAVES ON YOUNG PLANTS OR VIGOROUS SPROUTS ARE
BROAD AND CORDATE, USUALLY WITH AN ACUMINATE TIP. LEAVES ON MATURE PLANTS EXPOSED TO FULL
SUN ARE NARROWER AND HASTATE, USUALLY ONLY SLIGHTLY ACUMINATE, AND TRUNCATE OR SLIGHTLY
TAPERING AT THE BASE, NOT CORDATE. INTERMEDIATE LEAF SHAPES CAN ALSO BE FOUND. THE LEAVES
ARE PUBESCENT, GIVING THEM A GRAY-GREEN APPEARANCE WHICH CONTRASTS SHARPLY WITH THE NORMAL
DARK GREEN OF CITRUS LEAVES. FRUITS ARE LARGE FOLLICLES (FIG. 2) ABOUT THE SIZE AND SHAPE OF
AVOCADOS AND HAVE A DEEP GROOVE ON ONE SIDE. THEY ARE GREEN UNTIL MATURITY, THEN TURN LIGHTER
GREEN, TAN, OR BROWN, AND OPEN TO RELEASE THE SEEDS. THE SEEDS HAVE COMAS OR PARACHUTES
ATTACHED, MAKING THEM EASILY WIND DISSEMINATED.
THE VINES OFTEN COMPLETELY COVER CITRUS AND OTHER TREES, SEVERELY SHADING AND STUNTING
THE HOST TREE (FIG. 3). THIS RESULTS IN REDUCED YIELDS AND HIGHER MAINTENANCE COSTS. VINES
ALSO GROW ON AND OVER FENCES, POWER LINE GUY WIRES, IRRIGATION PIPES, AND ANY OTHER AVAILABLE
SUPPORT.

LITERATURE CITED:
1. BAILEY, L. H. 1928 (REPRINTED 1961). STANDARD CYCLOPEDIA OF HORTICULTURE. MACMILLAN CO.
NEW YORK. 3639 P. [ORRENIA ODORATA P. 2069].
S 2. BURNETT, H. C. 1973. THE MILKWEED VINE AND A NEWLY OBSERVED CERCOSPORA LEAF SPOT.
FLA. DEPT. AGR. & CONSUMER SERVE DIV. PLANT IND., PLANT PATHOL. CIRC. 126; 2 P.
3. BURNETT, H. C., D. P. H. TUCKER, M. E. PATTERSON, AND W. H. RIDINGS. 1973. BIOLOGICAL
CONTROL OF MILKWEED VINE WITH A RACE OF PHYTOPHTHORA CITROPHTHORA. PROC. FLA. STATE
HORT. SOC. 86:111-115.
CONTRIBUTION NO. N-147, BUREAU OF NEMATOLOGY







4. BURNETT, H. C., D. P. H. TUCKER, AND W. H. RIDINGS. 1974. PHYTOPHTHORA ROOT AND STEM
ROT OF MILKWEED VINE. PLANT DIS. REPTR. 58(4):355-357.
5. LINDLEY, J. 1838. MISCELLANEOUS NOTES 71. THE BOTANICAL REGISTER. LONDON.
6. MORONG, T., AND N. L. BRITTON. 1892. AN ENUMERATION OF THE PLANTS COLLECTED BY DR.
THOMAS MORONG IN PARAGUAY, 1888-1890. ANN. N. Y. ACAD. SCI. 7:45-280. [MORRENIA
ODORATA, P. 164].
7. PHILLIPS, R. L., AND D. P. H. TUCKER. 1970. MILKWEED VINE CONTROL IN FLORIDA CITRUS
GROVES. PROC. FLA. STATE HORT. SOC., 83:26-29.
8. PHILLIPS, R. L., AND D. P. H. TUCKER. 1973. AN EVALUATION OF NEW HERBICIDES FOR
MILKWEED VINE CONTROL. PROC. FLA. STATE HORT. SOC. 86:29-33.
9. RIDINGS, W. H., H. C. BURNETT, AND C. P. SEYMOUR. 1974. MILKWEED VINE, A GROWING
PEST OF CITRUS. FLA. DEPT. AGR. & CONSUMER SERVE DIV. PLANT IND., PLANT PATHOL.
CIRC. 147; 2P.
10. RYAN, G. F., AND L. C. KNORR. 1967. MILKWEED VINE: A SPREADING MENACE IN CITRUS
GROVES. CITRUS IND. 48(5):8, 10, 30.
11. TUCKER, D. P. H., R. L. PHILLIPS, AND J. L. JACKSON, JR. 1971. THE MILKWEED VINE -
CURRENT RECOMMENDATIONS AND PROMISING NEW APPROACHES. PROC. FLA. STATE HORT.
Soc. 84:41-44.
























FIG. 1. LEAF SHAPES OF MORRENIA ODORATA.






i.4








Al


FIG. 2. FRUIT OF
MORRENIA ODORATA.


FIG. 3. VINE OF MORRENIA ODORATA GROWING
OVER AND COVERING A CITRUS TREE.