Pentas lanceolata
Pentas lanceolata is a durable tropical perennial hardy in USDA Hardiness Zones 8b-11. It can be used as a containerized ornamanetal or bedding plant. Pentas performs best in fertile, well-drained soils in full sun.
Fertilizer recommendations for greenhouse culture are nitrogen at 175 to 200 parts per million from a complete fertilizer. Pentas can reduce the pH of the growing medium, and they are susceptible to iron toxicity from low pH. Maintain a medium pH of 6.5 to 7.0 and avoid acidic high-ammonium fertilizers and supplemental iron.
Symptoms of iron toxicity include leaf rolling, interveinal chlorosis to spotting on mature leaves and eventually leaf abscission. Plants are also susceptible to magnesium deficiency (lower leaf interveinal chlorosis), especially during the onset of flowering.
Fertility monitoring and management for P. lanceolata require balancing the plant’s needs. Manage the root substrate pH and electrical conductivity and provide adequate, but not excessive, levels of all essential elements.
Using a plant diagnostic laboratory to identify problems is still the best way to ensure accurate diagnoses, since many nutritional, physiological, insect and disease problems mimic each other.
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Nutrient-deficiency descriptions are unavailable for most perennials, yet growers must often make quick diagnoses. A research project initiated at
Pictures related to the nutrient deficiencies series may accessed by viewing the PDF files of the pages that originally appeared in GMPRO magazine: Page 1. Page 2. Page 3. Page 4. Page 5.
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Nitrogen (N)
Nitrogen-deficient plants are smaller with less shoot growth.
As symptoms progress, a patchy chlorosis develops on mature leaf margins. Brownish-red tip necrosis also occurs.
At the advanced stage, veins become dull yellow and tips of older leaves express papery tan necrosis.
Phosphorus (P)
Phosphorus-deficient plants have darker-green foliage and shorter internodes than the control.
Oldest to youngest leaves are darker green when compared to the control.
Under advanced symptoms, a faint splotchy yellow chlorosis appears on recently mature and mature leaves. A thin band of necrotic tissue develops on margins of recently mature leaves.
Potassium (K)
Potassium-deficient plants have smaller, darker-green leaves with shorter internodes when compared to the control.
Potassium-deficient plants then express a faint interveinal chlorosis on recently mature leaves.
Finally, the older leaves express a reddish-brown necrosis on the margins and leaf bases.
Calcium (Ca)
Calcium-deficient plants have spindly stems and smaller axillary shoots. Flowering is delayed.
Eventually the flower stems topple and the young shoots become deformed. Necrosis quickly develops on young, straplike leaves.
Here are calcium-deficiency symptoms on mature (translucent tissue on the leaf base), young (tan necrotic patches on the base) and youngest leaves (scorched necrosis).
Magnesium (Mg)
Magnesium deficiency begins as a faint interveinal chlorosis on recently mature leaves. Young leaves are deep green.
As symptoms progress, a greenish-yellow interveinal chlorosis appears over the entire leaf blade.
Advanced symptoms (dull-green, irregular-shaped patches and tannish-brown spots) appear on the leaf margins and quickly move toward the midveins. Magnesium-deficient leaves are smaller than the control.
Sulfur (S)
Sulfur-deficient plants have thinner stems with a more upright architecture when compared to the control.
As symptoms progress, a distinct yellow-green interveinal chlorosis appears on the youngest, young and recently mature leaves.
Young leaves are straplike. Recently mature leaves have pale greenish-white bases.
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Boron (B)
Boron-deficient plants initially express compressed shoot tips and deformed young leaves.
At the advanced stage, deformed youngest and brittle young leaves have necrotic margins. Flowers cease development.
Copper (Cu)
Copper-deficient plants have shorter internodes when compared to the control and express dull-blue-green foliage.
As symptoms progress, shoot growth is limited and leaves appear narrower than the control.
This is a comparison of copper-deficient leaves (bottom) to the control (top). Note the small, splotchy yellow chlorotic spots on the oldest leaves of copper-deficient plants.
Iron (Fe)
Iron-deficient plants first express lighter-green recently mature leaves.
This is a close-up of the light-green interveinal chlorosis on recently mature leaves.
Advanced symptoms include a yellowish-white interveinal chlorosis on the bases of mature leaves and light-yellow areas on recently mature and young leaves.
Manganese (Mn)
Manganese deficiency begins with the recently mature leaf bases developing a faint chlorosis.
As symptoms progress, the recently mature leaves express a distinct interveinal chlorosis.
Zinc (Zn)
Shoot growth on zinc-deficient plants is less dense and more rigid and upright than the control.
Under advanced deficiency, plants are severely stunted with papery necrotic spots on young leaves.
- James L. Gibson, Jude Groninger,
James Gibson is assistant professor, Jude Groninger is senior laboratory technician, Sharon Wombles is a former undergraduate research assistant and Kathryn Campbell is an undergraduate research assistant, University of Florida, Institute of Food and Agricultural Sciences,(850) 983-5216, Ext. 103;
The authors thank Fred C. Gloeckner Foundation for grant support, Smithers-Oasis for propagation medium, Rick Schoellhorn for plant material and Quality Analytical Laboratories for tissue analysis. The authors also thank Christopher Cerveny, Leah McCue, and MariahWilliams for technical assistance.
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