Dahlia Doctor Research Library: What Shapes Dahlia Tuber Yield and Quality

A Curated Knowledge Card Collection

Copyright © 2026 by Steve K. Lloyd.
All Rights Reserved.

Dahlia growers often talk about tubers as if they are simply the end-of-season result of a healthy plant. But the research record shows a more complicated picture. Tuber yield and tuber quality are shaped by cultivar genetics, planting date, nutrition, pinching, plant density, defoliation, regional climate, and the way a plant divides energy between flowers, shoots, and underground storage roots.

This collection brings together Dahlia Doctor Knowledge Cards focused on dahlia tuber yield and tuber quality. It is separate from the earlier collection on tuber formation. Here, the emphasis is not simply whether a dahlia forms tuberous roots, but how many usable tubers it produces, how large or heavy those tubers become, and which growing practices appear to improve or reduce the crop of planting stock.

The selected studies include planting-date trials, cultivar and genotype comparisons, nutrient-management experiments, pinching and organic-manure studies, and older research on tuberous-root production. Together, they show that tuber production is not controlled by one factor. A cultivar with strong genetic potential can still respond differently depending on fertility, spacing, defoliation, season length, and management. Likewise, a treatment that improves flower production may not always maximize tuber weight or tuber number.

For growers, the practical message is clear: tuber quality begins before storage. It is built through the whole growing season, from the starting plant material and planting date to nutrition, canopy management, and the plant's late-season opportunity to move resources underground.

Each post in this series presents a curated set of Dahlia Doctor Knowledge Cards organized around a specific research topic. A Knowledge Card summarizes one scientific or technical source using a consistent structure: study system, experimental context, experimental design, key results, mechanistic insight, practical guidance, and why the source matters to dahlia growers and researchers. These summaries represent original interpretive work. They are intended as a research guide, not a substitute for reading the original papers. Each citation title links to a Google Scholar search for that source, opening in a new tab, to help you locate the original publication independently.

Each Knowledge Card appears once in this collection, placed in the topic cluster where it contributes most directly. Some sources are relevant to more than one cluster; placement reflects primary emphasis rather than exclusive relevance. KC-0796, which examines phosphorus fertilization, planting density, and defoliation effects on tuberous root dry matter, addresses both nutritional and source-sink management themes; it is placed in the agronomic management cluster where its source-sink emphasis is strongest.

Publication Type

Experimental Research Article

Full Citation

Kumar, M., Thakur, P., Kashyap, B., Kumar, P., Sharma, A., Bhardwaj, R., & Shah, A. H. (2024). Effect of different planting dates on tuber production in dahlia (Dahlia variabilis L.) in low hill conditions of Himachal Pradesh, India. Plant Cell Biotechnology and Molecular Biology, 25(7–8), 71–78.

Study System

Dahlia variabilis L.; five cultivars — Anarkali, Gargi, Giani Zail Singh, Matungini, and Suryadev — grown from rooted cuttings for tuber production.

Experimental Context

Field evaluation under low hill conditions in Himachal Pradesh, India, comparing three planting-date treatments across five cultivars.

Experimental Design

Factorial randomized block design with five cultivars and three planting-date treatments, three replications, 15 treatment combinations, and 45 experimental plots. Rooted cuttings were planted at 45 cm × 45 cm spacing with nine plants per plot. Recorded traits included plant height, plant spread, internodal length, number of tubers per plant, tuber diameter, tuber length, tuber weight per plant, and tuber yield per plot.

Key Results

Suryadev had the greatest mean plant height and internodal length. Matungini had the greatest mean plant spread, number of tubers per plant, and tuber length. Giani Zail Singh had the greatest mean tuber diameter. Anarkali had the greatest mean tuber weight per plant and tuber yield per plot. Across planting dates, October 15 produced the highest mean number of tubers per plant, tuber diameter, tuber length, tuber weight per plant, and tuber yield per plot.

Mechanistic Insight

The authors attributed cultivar differences in plant traits and tuber production to genetic traits, environmental conditions, soil composition, and cultivar responses to local environmental circumstances. These factors were identified as influencing tuber development and tuber weight, though the study did not separate genetic and environmental contributions experimentally.

Practical Guidance

October 15 was identified as the most suitable planting date for tuber production and tuber characteristics under the tested low hill conditions. Among the five cultivars, Anarkali was most productive for tuber weight and tuber yield per plot, Matungini for tuber number and tuber length, and Giani Zail Singh for tuber diameter.

Why This Source Matters

This study demonstrates that both planting date and cultivar choice independently influence tuber production outcomes, and that the cultivar producing the most tubers by number is not necessarily the cultivar producing the most tuber weight per plant. The cultivar-by-trait pattern — with different varieties leading different measurements — is a useful reminder that “best for tubers” is not a single-dimensional ranking. Results are specific to the low hill conditions and growing season reported, and direct transfer to other climates or planting systems should be approached with caution. The source contains an internal discrepancy in planting-date labels: the abstract and methods list September 15, October 15, and November 15, while the results tables and discussion use October 15, November 15, and December 15; this entry follows the results-table dates because they are attached to the reported tuber-production data.

Publication Type

Experimental Research Summary

Full Citation

Tuchiya, S. (1993). Studies on the production of tuberous roots in dahlia. Special Bulletin of Ishikawa Agricultural College, 18, 70–73.

Study System

Dahlia tuberous roots, seed tuberous roots, cuttings, and plants grown under daylength, temperature, planting-time, harvesting-time, nutrient, and dormancy treatments.

Experimental Context

Production studies focused on the occurrence and development of dahlia tuberous roots, the proportion of useful tuberous roots with buds attached, and production conditions affecting tuberous root formation, thickening, dormancy, and nondormancy.

Experimental Design

A series of studies examining root and tuberous-root occurrence, tuberous-root weight classes, planting time, cutting time, top cutting after September, harvest timing, long-day and short-day conditions, nutrient uptake and distribution, 6-benzylaminopurine sprays, cold storage after harvest, and day/night temperature conditions.

Key Results

Useful tuberous roots — those with buds attached — were one-half to one-third of total tuberous roots formed during the growing period. Most roots appeared on the stem below the fourth node. Seventy percent of tuberous roots appeared by mid-July, within approximately 2.5 months after planting. Tuberous roots weighing 20 to 70 g showed no differences in winter survival, sprouting rate, growth, or flowering the following year. Delayed planting and delayed cutting reduced tuberous-root weight or number. A growth period of more than six weeks before vigorous thickening was needed to produce seed tuberous roots. Tuberous-root dry matter and carbohydrates increased markedly from mid-September to mid-November. More than 15 days under short-day conditions, following more than six weeks under long-day conditions, increased the percentage of plants forming tuberous roots and produced heavier and more uniform tuberous roots than fewer than 10 days of short-day exposure. Short-day response varied among varieties. Nutrient elements stored in the top were transferred to tuberous roots during thickening. Storage at 0°C for 30 days after harvest broke dormancy and stimulated sprouting. Plants grown under long-day conditions or low night temperature produced nondormant tuberous roots.

Mechanistic Insight

Dahlia tuberous roots do not produce adventitious buds from their surfaces and can sprout only from eyes or definite buds on attached old stem tissue. Useful tuberous-root production depended on roots occurring near buds. Long-day growth before short-day exposure supported production of heavier tuberous roots enriched with carbohydrates. Nutrient elements accumulated in the top during vegetative growth and were later transferred to tuberous roots during thickening. Low-temperature storage broke dormancy in harvested tuberous roots.

Practical Guidance

Seed tuberous roots require attached old stem tissue containing a bud. Tuberous roots weighing 20 to 70 g were adequate as seed tuberous roots in the tested cultivar. Planting before mid-June and planting cuttings before July 1 produced larger tuberous roots. Mid-November was identified as the optimum harvest time. Fertilizer application until late September was identified as important for tuberous-root production. Year-round production and supply of nondormant tuberous roots are possible by growing dahlia plants under long-day conditions or at night temperatures below 10°C.

Why This Source Matters

This is one of the few sources in the dahlia literature to treat tuberous-root production as a system — integrating planting timing, cutting timing, harvest date, daylength response, nutrient transfer, dormancy, and seed tuber selection within a single research program. The finding that useful tuberous roots (those with buds) are only one-half to one-third of total roots formed has direct implications for how growers should think about tuber yield: the harvest count is not the usable planting-stock count. The daylength interaction data — specifically the threshold of more than 15 days of short-day exposure to produce heavier, more uniform tuberous roots — also places this study in productive dialogue with the physiological tuberization literature. As an older Japanese source published in a regional bulletin, it is less frequently cited than it deserves.

Publication Type

Experimental Research Article

Full Citation

Nag, K., & Tamrakar, S. K. (2023). Evaluation of different dahlia (Dahlia variabilis L.) cultivars for tuber yield. Journal of Krishi Vigyan, 11(2), 150–153. 

Study System

Twenty dahlia cultivars grown for tuber production under Chhattisgarh plains conditions during the 2019–20 to 2020–21 growing period.

Experimental Context

Cultivar evaluation at a horticultural research farm in Raipur, addressing the need for cultivar selection for quality planting material and higher tuber yield in Chhattisgarh plains conditions. The research field had clay-loam soil with neutral pH.

Experimental Design

Twenty cultivars grown in a randomized block design with three replications. Standard dahlia cultivation practices were followed. Observations were recorded from five randomly selected plants per plot, with border plants excluded. Plots were irrigated weekly during initial growth and every 10 to 12 days during later growth.

Key Results

Blackout Black recorded the highest number of tubers per plant, number of tubers per plot, tuber weight, tuber yield per plant, tuber yield per plot, and tuber yield per hectare. Blackout Black produced 7.96 tubers per plant, 113.70 tubers per plot, 86.29 g tuber weight, 86.95 g tuber yield per plant, 1.78 kg tuber yield per plot, and 2.52 t/ha tuber yield. Kenya Blue was statistically at par for number of tubers per plant. Jishu Red and Sachin Red were statistically at par for tuber weight and tuber yield per plot. Kenya Original, Jishu Red, and Sachin Red were statistically at par for tuber yield per hectare. Anita Orange Red with Gold recorded the lowest values across all measured tuber-yield parameters.

Mechanistic Insight

The authors attributed variation in tuber yield per plant to differences in plant height, number of branches, and photosynthate synthesis. Variation in tuber weight among cultivars was attributed to genetic differences and local environmental conditions, including soil structure and texture.

Practical Guidance

Blackout Black was identified as the most suitable cultivar among the 20 tested for higher tuber number and tuber yield under Chhattisgarh plains conditions. The magnitude of cultivar variation — from the lowest to the highest performer — was large enough to make cultivar selection a primary management decision for growers focused on planting-stock production.

Why This Source Matters

This is one of the most direct cultivar-by-tuber-yield comparison studies in the current dahlia literature, evaluating 20 cultivars under uniform conditions across two growing seasons. The range of outcomes across the 20 cultivars confirms that genetic differences in tuber yield potential are large and not simply mediated by plant size. The study also illustrates the difference between tuber number and tuber weight as separate, not interchangeable, yield components — a distinction relevant to growers who evaluate their planting stock by count, by mass, or both.

Publication Type

Journal Article

Full Citation

Manjula, B. S., Nataraj, S. K., Hegde, P. P., Anitha, G., & Ayesha, N. (2017). Evaluation of dahlia genotypes (Dahlia variabilis L.) for growth, yield and quality traits under hill zone of Karnataka. Environment & Ecology, 35(4C), 3158–3161. 

Study System

Dahlia variabilis L. genotypes evaluated under hill zone field conditions in Karnataka, India.

Experimental Context

Field evaluation of 25 genotypes for growth, flowering, yield, and quality traits under defined hill zone conditions.

Experimental Design

Randomized complete block design with 25 genotypes evaluated for growth, flowering, yield, and quality traits, with measurements including plant height, branching, flowering time, flower number, tuber number, flower weight, stalk length, and vase life.

Key Results

Significant genotypic differences were found for plant height, branching, flowering time, flower number, tuber number, flower weight, stalk length, and vase life. Genotype-driven variation was observed across both yield and quality traits.

Mechanistic Insight

Genotype-driven variation in growth allocation and source-sink relationships was identified as influencing yield and quality trait expression across the 25 genotypes tested.

Practical Guidance

Genotype choice should match production goals, whether the priority is tuber yield, cut-flower quality, or early flowering, since no single genotype performed best across all measured traits.

Why This Source Matters

This study demonstrates that tuber number is among the traits showing significant genotypic variation in a field comparison of 25 genotypes under a single set of environmental conditions. Unlike studies that compare a small number of named cultivars, the 25-genotype design captures a wider range of genetic diversity and gives a clearer picture of how much variability in tuber performance is attributable to genotype alone, independent of management differences. The hill zone context also adds regional relevance for growers in comparable environments.

Publication Type

Experimental Research Article

Full Citation

Singh, H. M., Mishra, U. S., & Mishra, T. S. (2017). Assessment of genetic variability for different characters of dahlia genotypes. HortFlora Research Spectrum, 6(4), 247–255.

Study System

Dahlia (Dahlia variabilis) genotypes; forty named varieties evaluated for vegetative, floral, and tuber traits under open-field winter-season conditions at an instructional horticulture farm in Kanpur, Uttar Pradesh, India, during 2011–12 and 2012–13.

Experimental Context

Two-season field evaluation of 40 varieties for sixteen vegetative, reproductive, and tuber-production traits.

Experimental Design

Randomized Block Design with three replications. Uniform-sized dahlia tubers of 3.0 to 4.0 cm diameter were planted in the first week of November on raised beds at 60 cm × 60 cm spacing. Each entry comprised 12 plants. Observations were recorded on five randomly selected plants per replication. Data were pooled and statistically analyzed.

Key Results

Wide variation was observed among the 40 varieties for all evaluated traits. Traits showing particularly large variation included plant height, number of branches per plant, number of flowers per plant, days required for bud emergence and bud maturity, flower bud length, flower diameter, number of tubers, and tuber weight. Tuber production per plant ranged from 5.133 to 12.413 in 2011–12. Single-tuber weight ranged from 0.163 kg to 0.613 kg in 2011–12 and from 0.170 kg to 0.498 kg in 2012–13.

Mechanistic Insight

Flower characters were stated to be expressed on the basis of the genetic constitution of the plant, species, or variety. The study did not separate additive and non-additive genetic components for tuber traits specifically, but the wide range of tuber number and tuber weight across the 40 varieties confirms that genetic differences make a large contribution to production variability.

Practical Guidance

The variation in tuber weight across the 40 varieties was identified as having a promising effect on sprouting and plant production in the following generation. Varieties differing substantially in single-tuber weight may produce different establishment rates and early-season vigor when used as planting stock.

Why This Source Matters

With 40 varieties evaluated across two seasons, this study provides one of the broader genetic-variability assessments available in the dahlia tuber-production literature. The tuber count range — from approximately 5 to 12 per plant — and the tuber-weight range — from under 200 g to over 600 g per tuber — quantify how large the performance spread can be within a species. That range has practical implications for anyone selecting parent material, evaluating planting stock, or comparing commercial cultivars: genetic potential for tuber yield varies enormously, and observed differences in production are not simply attributable to management.

Publication Type

Experimental Research Article

Full Citation

Pandey, S. K., Kumari, S., Singh, D., Singh, V. K., & Prasad, V. M. (2017). Effect of biofertilizers and organic manures on plant growth, flowering and tuber production of dahlia (Dahlia variabilis L.) cv. SP Kamala. International Journal of Pure & Applied Bioscience, 5(2), 549–555. 

Study System

Dahlia variabilis cv. ‘SP Kamala’ seedlings grown under field conditions in Allahabad, Uttar Pradesh, India, from November 2012 to March 2013. The experimental soil was sandy loam, moderately fertile, with pH 7.2.

Experimental Context

Field experiment evaluating biofertilizer and organic manure treatment combinations for dahlia growth, flowering, and tuber production.

Experimental Design

Randomized block design with ten treatments and three replications. Twenty-five-day-old seedlings with 3 to 5 leaves were transplanted at 60 × 60 cm spacing, with nine seedlings per plot. Treatments included a control with recommended NPK, farmyard manure, vermicompost, Azotobacter, Azospirillum, and phosphorus-solubilizing bacteria in different combinations. Vegetative, flowering, tuber-production, and benefit-cost parameters were analyzed by ANOVA with critical difference calculated at the 5 percent significance level.

Key Results

The treatment combining vermicompost at 2.5 t/ha, Azotobacter at 2.0 kg/ha, and phosphorus-solubilizing bacteria at 2.0 kg/ha produced the highest plant height, number of primary branches, number of flowers per plant, flower yield per plant, flower yield per hectare, tuber weight, number of tubers per plant, tuber yield per plant, tuber yield per hectare, and benefit-cost ratio. The treatment combining farmyard manure, Azospirillum, and phosphorus-solubilizing bacteria produced the highest flower size. The control produced the lowest values across several flowering and tuber-production measurements.

Mechanistic Insight

The authors attributed treatment effects to the combined action of organic manures supplying nutrients to microbes and improving soil porosity, and biofertilizers enriching soil nutrient quality through microbial activity. The study did not isolate individual mechanisms for each treatment component.

Practical Guidance

The combination of vermicompost at 2.5 t/ha with Azotobacter and phosphorus-solubilizing bacteria was identified as superior for plant growth, flower yield, tuber yield, and benefit-cost ratio in this cultivar and location. Results should be adapted to local soil conditions before direct application.

Why This Source Matters

This study demonstrates that the combination of organic carbon input and microbial inoculants can simultaneously increase both flower yield and tuber yield, suggesting that the treatments act on overall plant productivity rather than shifting allocation between flowers and tubers in a simple tradeoff. The benefit-cost data also make this a practically framed source, connecting agronomic inputs to economic return rather than only reporting biological measurements.

Publication Type

Experimental Research Article

Full Citation

Raghunandan, T., Collis, J. P., Saravanan, S., & Barman, K. S. (2021). Effect of integrated nutrient management on plant growth and tuber yield of dahlia (Dahlia variabilis) cv. Kenya White. International Journal of Plant & Soil Science, 33(24), 80–84.

Study System

Dahlia variabilis cv. Kenya White grown under field conditions during the spring growing season under Allahabad agro-climatic conditions.

Experimental Context

Field evaluation of 13 fertilizer, organic manure, and biofertilizer treatment combinations for plant growth and tuber yield.

Experimental Design

Randomized complete block design with three replications. Treatments included recommended NPK fertilizer dose alone and reduced recommended fertilizer doses combined with Azotobacter, farmyard manure, vermicompost, or combined organic and biofertilizer inputs. Forty-day-old seedlings were transplanted at 45 cm × 60 cm spacing.

Key Results

The treatment combining 75% recommended fertilizer dose with Azotobacter at 2.5 kg/ha, farmyard manure at 10 t/ha, and vermicompost at 10 t/ha recorded the highest plant height, plant spread, number of branches per plant, number of leaves per plant, tuber weight, number of tubers per plant, and tuber yield per plant. The control treatment recorded the lowest growth parameters.

Mechanistic Insight

The authors attributed the highest-performing treatment to combined nutrient supply from inorganic fertilizer, organic manure, vermicompost, and Azotobacter, with potential contributions including improved nutrient availability, nitrogen fixation, phosphorus solubilization, growth-promoter production, photosynthetic activity, carbohydrate synthesis, root formation, and transfer of assimilates into tuber development.

Practical Guidance

A treatment combining 75% recommended fertilizer dose with Azotobacter at 2.5 kg/ha, farmyard manure at 10 t/ha, and vermicompost at 10 t/ha produced the highest measured growth and tuber yield parameters in this trial. Notably, the best treatment did not use the full recommended fertilizer dose, suggesting that organic and biological inputs can partially offset reduced inorganic fertilizer rates without reducing yield outcomes.

Why This Source Matters

This study adds to the picture built by KC-0017 by showing that integrated nutrient management at a reduced inorganic fertilizer rate can match or exceed outcomes from a full inorganic dose. The finding that 75% NPK combined with organic and biological inputs outperformed 100% NPK alone has practical implications for growers interested in reducing fertilizer inputs without sacrificing tuber yield. Read alongside KC-0017, KC-0295, KC-0380, and KC-0819, it is part of a consistent pattern across multiple trials and cultivars: combined organic and inorganic nutrition outperforms either input type alone.

Publication Type

Journal Article

Full Citation

Gupta, Y. C., Dinesh, R. V., Kashyap, B., Bhatia, S., & Sharma, P. (2016). Effect of N and K on growth, flowering and multiplication of Dahlia (Dahlia variabilis) cv. 'Giani Zail Singh'. Current Horticulture, 4(2), 48–53.

Study System

Dahlia variabilis cv. 'Giani Zail Singh' grown under mid-hill field conditions.

Experimental Context

Field evaluation of nitrogen and potassium effects at multiple levels on growth, flowering, and tuber multiplication.

Experimental Design

Factorial randomized block design with four nitrogen levels and four potassium levels, with basal and split fertilizer application and measurement of growth, flowering, and tuber traits.

Key Results

Highest growth, flower quality, and tuber yield occurred with 30 g/m² nitrogen plus 24 g/m² potassium. Earliest flowering occurred in control plots, indicating that higher nutrient inputs delayed but improved flowering in this cultivar.

Mechanistic Insight

Nitrogen and potassium together may enhance vegetative growth, assimilate production, and allocation to both flowers and tubers, though the study did not isolate individual nutrient mechanisms.

Practical Guidance

In this cultivar and field context, 30 g/m² nitrogen plus 24 g/m² potassium maximized several flower and tuber traits. The authors advise adapting application rates to soil testing, cultivar, and production goal, as optimal rates will vary by site and target.

Why This Source Matters

This is one of the few studies in this collection to evaluate nitrogen and potassium together as a factorial combination rather than as part of a broader integrated fertility trial. Isolating N and K from other inputs allows a cleaner interpretation of how macronutrient balance affects tuber yield — a useful contrast to the more complex treatment structures in KC-0017, KC-0066, KC-0380, and KC-0819. The finding that the control plots flowered earliest also illustrates a recurring tension in dahlia production: inputs that maximize tuber yield may shift the timing of flowering.

Publication Type

Journal Article

Full Citation

Kumar, N., Prasad, V., & Pal Yadav, N. (2019). Effect of chemical fertilizers and bio fertilizers on flower yield, tuberous root yield and quality parameter on dahlia (Dahlia variabilis L.) cv. Kenya Orange. Journal of Pharmacognosy and Phytochemistry, 8(4), 2265–2267.

Study System

Dahlia variabilis cv. Kenya Orange grown under field conditions.

Experimental Context

Field evaluation of NPK and biofertilizer treatment combinations for flower yield and tuberous root yield and quality.

Experimental Design

Randomized Block Design with 13 fertilizer treatments combining NPK with Azotobacter or phosphorus-solubilizing bacteria; three replications.

Key Results

The treatment designated T3 maximized flower yield and vase life. The treatment designated T10 maximized tuber number, tuber size, and tuber yield. The treatment producing the best flower outcome was not the same treatment producing the best tuber outcome.

Mechanistic Insight

Nutrient balance and biofertilizer-mediated nitrogen and phosphorus availability alter biomass allocation between flowering and tuber formation. The divergence between the best-flower and best-tuber treatments suggests that different nutrient inputs influence the plant's allocation priorities in different directions.

Practical Guidance

Integrated fertilizer management can be adjusted for either flower production or tuber yield depending on production goals. Growers optimizing for cut-flower yield and growers optimizing for planting-stock tuber yield may need different treatment approaches even within the same cultivar and site.

Why This Source Matters

This study provides direct evidence of a production-goal tradeoff: the treatment maximizing flower yield in cv. Kenya Orange was not the treatment maximizing tuber yield. That finding is practically significant for growers who divide their dahlia operation between cut-flower sales and tuber stock production. It also reinforces a theme running through the nutrition cluster of this collection — that the question "which fertilizer treatment is best?" cannot be answered without specifying what "best" means in terms of production target.

Publication Type

Experimental Research Article

Full Citation

Barik, I. (2017). Effect of N, P, K and organic manures on flower yield and flower quality of dahlia (Dahlia variabilis) hybrid 'Eternity Sports'. Environment & Ecology, 35(4E), 3664–3668.

Study System

Dahlia variabilis hybrid 'Eternity Sports' grown in a field trial during the rabi season.

Experimental Context

Field trial comparing inorganic NPK fertilizer with farmyard manure, vermicompost, and poultry manure combinations for flowering, cut-flower quality, flower yield, tuber number, and tuber yield.

Experimental Design

Randomized block design with 13 treatments and 3 replications. Treatments included a control, full NPK, 75% NPK with 25% organic manure sources, 50% NPK with 50% organic manure sources, 25% NPK with 75% organic manure sources, and a combination of equal parts farmyard manure, vermicompost, and poultry manure.

Key Results

The 50% NPK plus 50% vermicompost treatment recorded 11 tubers per plant, 66 tubers per plot, 637.99 g tuber yield per plant, 3.82 kg tuber yield per plot, and 25.35 t/ha tuber yield per hectare, along with the longest flowering duration and the greatest number of flowers per plant. The 50% NPK plus 50% poultry manure treatment recorded the highest single flower weight and single tuber weight.

Mechanistic Insight

The authors attributed improvements under the 50% NPK plus 50% vermicompost treatment to balanced nutrient availability, improved root proliferation, enhanced microbial activity, improved NPK uptake, and enhanced photosynthetic activity. Higher flower and tuber weight under the poultry manure treatment were attributed to nutrient solubilization during composting and bacterial activity in chicken manure.

Practical Guidance

Application of 50% NPK plus 50% vermicompost was identified as beneficial for plant growth, flower yield, tuber yield, and flower quality. Application of 50% NPK plus 50% poultry manure was identified as significant for single flower weight and single tuber weight. Growers targeting overall tuber yield may favor the vermicompost combination; growers interested in larger individual tubers may find the poultry manure combination more relevant.

Why This Source Matters

This study adds a useful distinction within the organic-input cluster: not all organic manure sources produce the same outcome. Vermicompost and poultry manure both improved tuber outcomes relative to the control, but they did so in different ways — vermicompost treatments drove higher tuber numbers and total yield, while poultry manure treatments drove higher individual tuber weight. That separation between total yield and individual tuber size is practically relevant for growers who need to meet minimum size standards for planting stock, cut-flower sales, or commercial distribution.

Publication Type

Experimental Research Article

Full Citation

Abdul Rahman, M., Prasad, V. M., Bahadur, V., & Fatmi, U. (2021). Study on effect of pinching and organic manures on growth, flowering and yield of Dahlia (Dahlia variabilis L.) cv. Red Symphony. Biological Forum – An International Journal, 13(3a), 1–6.

Study System

Dahlia variabilis cv. Red Symphony grown during the winter season in Prayagraj, Uttar Pradesh, India.

Experimental Context

Evaluation of pinching at different days after transplanting in combination with organic manure sources for dahlia growth, flowering, flower yield, and tuber yield.

Experimental Design

Randomized block design with thirteen treatments and three replications. Treatments compared control, no pinching, and pinching at 40, 45, or 50 days after transplanting, each combined with farmyard manure at 10 t/ha, vermicompost at 5 t/ha, or poultry manure at 3 t/ha. Seedlings were planted at 60 cm × 80 cm spacing.

Key Results

No pinching with poultry manure produced the greatest plant height, earliest first flower bud initiation, largest flower diameter, and highest single-flower weight. Pinching at 40 days after transplanting with poultry manure produced the greatest plant spread, number of leaves, number of branches, number of flowers per plant, pedicel length, flower yield per plant, flower yield per hectare, tuber weight, number of tubers per plant, tuber yield per plant, tuber yield per hectare, and cost-benefit ratio. Pinching at 40 days after transplanting with vermicompost and with farmyard manure were identified as next-best treatments.

Mechanistic Insight

Pinching increased lateral growth and flower number but reduced flower size in this trial. Pinching during chilly winter conditions delayed lateral bud emergence. Organic manure treatments were associated with differences in vegetative growth, flowering, flower yield, and tuber yield, though individual mechanisms were not separated experimentally.

Practical Guidance

Pinching at 40 days after transplanting combined with poultry manure at 3 t/ha was identified as the best-performing treatment for overall growth, flowering, flower yield, tuber yield, and economic return under the study conditions. The tradeoff is clear: unpinched plants produced the largest individual flowers, while pinched plants produced more flowers and more tubers per plant. Different pinching times also produced flowering at different intervals, which growers can use to stagger harvest timing.

Why This Source Matters

This study is the only entry in this collection to explicitly connect canopy architecture management — pinching — with tuber yield outcomes. The finding that pinching at 40 days after transplanting with poultry manure simultaneously maximized flower number, tuber number, tuber weight, and cost-benefit ratio is noteworthy because it suggests that practices affecting shoot architecture can redirect assimilate partitioning in ways that benefit both the aerial and underground yield. The tradeoff with single-flower size, however, means that the best practice for planting-stock production is not the same as the best practice for cut-flower quality.

Publication Type

Journal Article

Full Citation

Yir, A. J., Delgado-Martinez, R., Morales-Rosales, E. J., Laguna-Cerda, A., Franco-Mora, O., & Sánchez, E. U. (2011). Tuberous root yield of Dahlia variabilis Wild (Desf.) under different agronomic management practices. Phyton, 80, 107–114.

Study System

Dahlia variabilis Wild (Desf.) grown under field and container conditions in Mexico during spring–summer 2009.

Experimental Context

Evaluation of phosphorus fertilization level, planting density, and partial defoliation on tuberous root dry matter production.

Experimental Design

Two factorial experiments in a randomized complete block design with four replications. The first tested four phosphorus levels combined with four planting densities. The second tested eight defoliation treatments. ANOVA and Tukey HSD tests were used for analysis.

Key Results

The highest tuberous root dry matter yield — 345 g/m² — was recorded at 120 kg P₂O₅/ha combined with 6.25 plants/m². Phosphorus alone at 120 kg P₂O₅/ha produced 264.3 g/m². Planting density alone at 6.25 plants/m² produced 214.8 g/m². Approximately two-thirds leaf area was sufficient to sustain root sink demand; complete defoliation reduced root dry weight by approximately 95%.

Mechanistic Insight

Increased phosphorus and planting density together increased leaf area and assimilate supply to roots. Approximately two-thirds of leaf area was sufficient to meet the sink demand of developing tuberous roots. Complete leaf removal eliminated carbon supply to roots, confirming that aboveground photosynthetic area is directly limiting for belowground storage.

Practical Guidance

Applying 120 kg P₂O₅/ha with a planting density of 6.25 plants/m² is recommended to maximize root dry matter under the tested conditions. Defoliation should be avoided; even partial defoliation approaching complete canopy removal causes severe reduction in tuberous root dry weight. Approximately 1,100 thermal units correspond to harvest maturity under the tested conditions.

Why This Source Matters

This is the most quantitatively explicit source in this collection on the relationship between canopy management and tuberous root yield. The defoliation data provide a direct demonstration of source limitation in dahlia tuber production: reducing leaf area by one-third is tolerable, but complete removal of photosynthetic area cuts root dry weight by 95%. That result has obvious implications for disease management, storm damage, and any practice that removes foliage during the tuber-bulking period. The phosphorus-by-density interaction also shows that nutrient management and spatial arrangement are not independent variables — their combined effect exceeds either factor alone.

The Knowledge Card summaries in this collection were developed from the Dahlia Doctor research archive and checked against available source records during editorial preparation. AI tools assisted with retrieval, formatting, comparison, and assembly of the collection. All curatorial decisions — including source selection, topic organization, interpretation, and final editorial framing — were made by the author.