Dahlia Doctor Research Library: Dahlia Tuber Storage, Dormancy, and Overwinter Survival

A Curated Knowledge Card Collection

Copyright © 2026 by Steve K. Lloyd
All Rights Reserved

Lifting dahlia tubers in autumn is the beginning of a months-long physiological process, not the end of the growing season’s demands. Whether tubers survive storage in good condition depends on how the storage environment manages three overlapping challenges: water loss, dormancy, and reserve chemistry. Too dry, and tubers desiccate. Too wet, and they rot. Too warm, and dormancy may break prematurely. Too cold, and some storage organs can lose water, lose viability, or shift their reserve chemistry in ways that affect spring performance.

This collection presents the research evidence on how storage substrate, temperature, humidity, and duration affect dahlia tuber survival, dormancy progression, and biochemical reserves across the overwintering window. It also includes evidence on the alternative of leaving tubers in the ground, and on the dormancy signaling that governs when tubers are physiologically ready to grow again.

The collection focuses on the overwintering window itself. Adjacent topics, including skin set and wound healing before storage, and tuber rot and bacterial disease during storage, are treated in the companion collections on lifting and curing readiness and on dahlia tuber rot, poppers, and clean stock.

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.

This collection focuses on the overwintering window: storage substrate and environment, dormancy and its release, in-ground versus lifted overwintering, and reserve chemistry changes during storage. It does not cover skin set, curing, or wound healing at lifting. Those topics are treated in the companion collection on lifting timing, skin set, curing, and storage readiness. Tuber rot, bacterial soft rot, and clean-stock systems are treated in the companion collection on dahlia tuber rot, poppers, and clean stock.

KC-0014, Ivanova and Zaprjanova (2020), appears here for its comparison of in-ground versus lifted-and-replanted overwintering outcomes. The same source appears in the companion collection on lifting timing and storage readiness, where its phenological data have additional application.

KC-0787, Van Leeuwen and Trompert (2005), is Zantedeschia research, not dahlia-direct evidence. It is included as adjacent geophyte support on drying conditions, storage temperature, desiccation, and subsequent growth, where it broadens the storage-environment picture. It does not carry the same evidentiary weight as the dahlia-direct sources in this cluster.

KC-0511, Zhao et al. (2022), is a broad ornamental geophyte dormancy review. It is included to provide mechanistic context for the dormancy signaling processes that govern when tubers are physiologically ready to grow again. The dahlia-direct dormancy evidence is KC-0213.

KC-0708, Cantor et al. (2016), is included as supporting context for pre-storage reserve accumulation rather than as a core storage-response source. Its primary contribution is establishing how cultivar and planting material affect soluble dry matter at harvest, which frames the reserve chemistry that enters storage.

Publication Type
Experimental Research Article

Full Citation
Ciobanu, I., Buta, E., Husti, A., & Cantor, M. (2015). Research regarding the influence of cultivar and storage substrate at Dahlia variabilis Desf. cactus type. Agricultura – Știință și practică, 95(3–4), 197–203.

Study System
Dahlia variabilis cactus-type cultivars ‘Kennemerland’, ‘Tsuki Yori No Sisha’, ‘Hayley Jane’, ‘Purple Gem’, and ‘Veritable’.

Experimental Context
Storage-substrate study of dahlia tuberous roots during the plant rest period, evaluating tuberous root weight and tuber number before and after storage.

Experimental Design
Tuberous roots from five cactus-type cultivars were stored in sand, sand plus sawdust at 70:30, or peat plus sawdust at 70:30. Four tuberous roots of each cultivar were placed in each substrate with three repetitions, for a total of 60 tuberous roots. Storage ran from November 8, 2014, to March 18, 2015, for 131 days, in a warehouse at 41 to 46°F (5 to 8°C) and 30 to 40% relative humidity. Tuberous roots were weighed and tubers counted before storage and after removal. Data were analyzed with the Duncan test.

Key Results
After 131 days, all tuberous roots showed weight loss varying by cultivar and substrate. The largest recorded losses were 0.11 kg for ‘Purple Gem’ in sand plus sawdust and ‘Veritable’ in sand, followed by 0.085 kg for ‘Kennemerland’ in sand. The smallest recorded losses were 0.02 kg for ‘Kennemerland’, ‘Tsuki Yori No Sisha’, and ‘Veritable’ in peat plus sawdust. Peat plus sawdust showed the best storage performance for tuberous root weight retention, while sand alone showed the poorest. ‘Purple Gem’ in peat plus sawdust had the highest post-storage weight at 0.41 kg. ‘Veritable’ in sand had the lowest at 0.09 kg. Most tuberous roots maintained the same number of tubers after storage.

Mechanistic Insight
Storage substrate affected maintenance of tuberous root weight during the rest period. Peat plus sawdust was associated with lower weight loss than sand alone across several cultivars, consistent with peat’s moisture-retention properties moderating desiccation during storage.

Practical Guidance
For the tested cactus-type dahlia cultivars, peat plus sawdust at a 70:30 ratio gave the best storage results for weight retention. Sand alone gave the poorest results.

Why This Source Matters
This is direct dahlia evidence on how substrate choice affects weight retention across the overwinter storage period. The cultivar-by-substrate interactions are a practical reminder that no single storage recommendation applies equally across all cultivars. Growers managing multiple cultivars with different tissue densities and desiccation tolerances may find that substrate choice is not a one-size answer.

Publication Type
Journal Article

Full Citation
Ciobanu, I., Cantor, M., Stefan, R., Buta, E., Magyari, K., & Baia, M. (2016). The influence of storage conditions on the biochemical composition and morphology of dahlia tubers. Notulae Botanicae Horti Agrobotanici Cluj-Napoca, 44(2), 459–465.

Study System
Dahlia hybrida tubers, cultivars ‘Kennemerland’ and ‘Red Pygmy’.

Experimental Context
Overwinter storage at 41 to 46°F (5 to 8°C) and 30 to 40% relative humidity in different substrates, with evaluation of morphological and biochemical changes.

Experimental Design
Factorial design with cultivar and substrate as factors. Substrates were sand, sand plus sawdust, peat plus sawdust, and no substrate. Biometric measurements were taken before and after storage. FT-IR and FT-Raman spectroscopy were used for comparative biochemical analysis of tuber tissue.

Key Results
Weight loss occurred in all treatments. Peat plus sawdust best preserved tuber mass; sand caused the highest weight loss. Tuber number remained mostly stable across treatments. Spectroscopic analysis showed higher inulin-related carbohydrate signals in tubers stored in sand. Polyacetylene compounds increased in tubers stored in peat plus sawdust.

Mechanistic Insight
Sand storage was associated with greater dehydration, which may concentrate inulin in remaining tissue and intensify the carbohydrate signal without indicating greater reserve accumulation. Polyacetylene increase in peat plus sawdust storage is consistent with a mild stress or pathogen-response signal in tissue that retained more moisture. Structural polysaccharides increased with storage duration across substrates.

Practical Guidance
Peat plus sawdust is recommended for dahlia tuber storage on the basis of mass retention. Sand increases dehydration risk. Substrate choice affects not only weight loss but also the biochemical profile of the tuber at the end of the storage period.

Why This Source Matters
This study extends the substrate comparison question beyond weight loss into tuber biochemistry. The spectroscopic evidence that storage conditions alter carbohydrate and secondary metabolite profiles, not just mass, adds a layer to the storage decision that is not visible in weight-loss data alone. For growers, the practical takeaway reinforces peat plus sawdust as the better substrate, but the biochemical findings suggest that what a tuber has been through during storage may affect its physiology at planting, not just its appearance.

Publication Type
Conference Proceedings Article

Full Citation
Van Leeuwen, P. J., & Trompert, J. P. T. (2005). Influence of drying conditions and storage temperature on desiccation and loss of tubers during storage and subsequent growth of Zantedeschia tubers. Acta Horticulturae, 673, 249–253.

Study System
Zantedeschia tubers (‘Mango’, ‘Treasure’, Z. albomaculata); postharvest drying and temperature-controlled storage until spring planting.

Experimental Context
Three-year factorial study examining the effects of postharvest drying and storage temperature on tuber losses, weight loss, and subsequent field performance.

Experimental Design
Tubers were dried for one week at 63°F (17°C) with air speeds of 0, 0.2, or 2.0 m s⁻¹, followed by storage at 48, 55, 63, or 68°F (9, 13, 17, or 20°C). Storage losses, weight loss, and subsequent yield were measured across three years.

Key Results
No-air drying increased rot and calcification. Storage at 48°F (9°C) caused the highest weight loss, lowest emergence, and lowest yield. Storage at 63 to 68°F (17 to 20°C) minimized calcification and losses.

Mechanistic Insight
Drying promotes protective skin formation, limiting infection and transpiration. Low storage temperatures increased desiccation and calcification in Zantedeschia, contrary to what might be assumed from general cold-storage principles. Higher storage temperatures within the tested range were associated with better outcomes for this geophyte.

Practical Guidance
Early drying with air circulation and storage above 55°F (13°C) reduced tuber loss and improved subsequent yield in Zantedeschia. The absence of air movement during drying was associated with increased rot and structural losses.

Why This Source Matters
This study is included as cautiously applicable geophyte evidence, not as dahlia-direct data. Zantedeschia is a monocot geophyte with different tissue architecture than dahlia, and its responses to storage temperature should not be assumed to transfer directly. What the study contributes is a documented example of a geophyte in which lower storage temperatures increased rather than decreased losses. This finding challenges the default assumption that colder is always safer. For dahlia growers, the practical implication is that the relationship between storage temperature and desiccation deserves attention, particularly for cultivars or storage situations where unexplained losses have occurred at low temperatures.

Publication Type
Journal Article

Full Citation
Konishi, K., & Inaba, K. (1967). Studies on flowering control of dahlia. VII. On dormancy of crown-tuber. Journal of the Japanese Society for Horticultural Science, 36(1), 131–140.

Study System
Dahlia crown-tubers; seasonal dormancy in a winter forcing and propagation context.

Experimental Context
Greenhouse planting trials designed to characterize dahlia crown-tuber dormancy and identify conditions that affect its depth and release.

Experimental Design
Greenhouse planting trials by harvest date; cultivar comparisons; cutting-time comparisons; low-temperature storage treatments at 32°F (0°C) for approximately 40 days.

Key Results
Sprouting and shoot growth were suppressed from October through mid-December. Dormancy depth varied by cultivar and propagation method. Storage at 32°F (0°C) for approximately 40 days broke dormancy and restored normal sprouting capacity.

Mechanistic Insight
Dormancy comprises an early rest phase followed by an after-rest phase. Chilling accelerates the physiological release of bud dormancy. Cultivar differences in dormancy depth and duration mean that a single forcing or storage schedule does not apply equally across the species.

Practical Guidance
Delay planting until dormancy has passed naturally, or apply extended low-temperature treatment to accelerate dormancy release. Account for cultivar-specific dormancy depth and propagation source when scheduling forcing or early spring planting.

Why This Source Matters
This is the primary dahlia-direct evidence in the collection on crown-tuber dormancy. The finding that October-through-December suppression of sprouting is a normal physiological condition, not a storage failure, has direct implications for how growers interpret tuber behavior in early winter. The chilling requirement for dormancy release explains why tubers that have been held too warm through winter may be slow to break dormancy in spring, and why cold-treated tubers can be brought into production earlier.

Publication Type
Review Article

Full Citation
Zhao, Y., Liu, C., Sui, J., Liang, J., Ge, J., Li, J., Pan, W., Yi, M., Du, Y., & Wu, J. (2022). A wake-up call: signaling in regulating ornamental geophytes dormancy. Ornamental Plant Research, 2(1), 1–10.

Study System
Ornamental geophytes including bulbs, corms, tubers, rhizomes, and tuberous roots.

Experimental Context
Review of dormancy regulation and dormancy release under seasonal cues across ornamental geophyte taxa.

Experimental Design
Narrative synthesis of physiological, hormonal, metabolic, and epigenetic studies on dormancy induction, maintenance, and release.

Key Results
Temperature and abscisic acid maintain dormancy. Gibberellin, cytokinins, sugars, and physical treatments including wounding promote dormancy release. Epigenetic mechanisms participate in the regulation of meristem reactivation.

Mechanistic Insight
Dormancy regulation involves integrated signaling among hormones, sugar metabolism, and epigenetic modification. Meristem reactivation is not a single threshold event but a coordinated response to multiple converging signals.

Practical Guidance
Temperature control, hormone management, and wounding can each be used to regulate dormancy release in ornamental geophytes. Understanding the signaling hierarchy helps explain why different management interventions have different effects on sprouting readiness.

Why This Source Matters
This review provides the broader mechanistic framework within which dahlia crown-tuber dormancy operates. KC-0213 established the chilling requirement and the seasonal dormancy window for dahlia; this review explains the hormonal and signaling architecture that underlies those observations across ornamental geophytes. For growers who want to understand why a cold storage period works, or why wounding sometimes accelerates sprouting, this source provides the physiological vocabulary.

Publication Type
Experimental Research Article

Full Citation
Ivanova, V., & Zaprjanova, N. (2020). Study on phenological behaviours of Dahlia variabilis Hort. in overwintering of tuberous roots in the soil. Scientific Papers. Series B, Horticulture, 64(1), 588–591.

Study System
Dahlia variabilis Hort.; cultivars ‘Vitus’, ‘White Ball’, and ‘Dark Red’; tuberous roots overwintered in soil compared with tuberous roots lifted, stored, and replanted.

Experimental Context
Field study in an ornamental planting context where standard local practice involved spring planting, autumn lifting, and winter storage in a dark ventilated place above 32°F (0°C).

Experimental Design
Tuberous roots of similar length and diameter were selected, each with part of the old stem. Control plants were lifted in the second half of October, cleaned, stored through winter, and replanted the following April. Experimental plants had stems cut to 10 cm in October and roots left in the soil for the next growing season. Vegetative and ornamental phenological traits were measured during the second vegetation period.

Key Results
Overwintered plants began sprouting 15 to 27 days earlier than lifted-and-replanted plants by cultivar, and mass emergence occurred 21 to 43 days earlier. Overwintered plants reached maximum growth earlier. Beginning of flowering occurred earlier by 5.2 to 13.1 days after emergence, and mass flowering occurred earlier by 8.17 to 14.4 days. Individual flowers lasted 1.7 to 5.4 days longer. Whole-plant flowering duration was longer by 37.9% to 45%.

Mechanistic Insight
The study identifies cultivar and overwintering treatment as factors associated with differences in emergence, growth rate, and flowering duration. Budding duration was not affected by cultivation mode, which the authors attributed to dahlia’s short-day classification.

Practical Guidance
Under the tested conditions, leaving tuberous roots in the soil produced earlier emergence, faster early growth, earlier flowering, and longer flowering duration compared with lifting, storing, and replanting. Future work should monitor soil temperature to characterize the thermal environment associated with these outcomes.

Why This Source Matters
For dahlia growers in climates where in-ground overwintering is possible, this study quantifies what is gained phenologically by not lifting. The earliness and extended flowering duration are not trivial differences. For growers in marginal climates, these data also frame the tradeoff: the earliness benefit of in-ground overwintering is real, but it comes with the risk of tuber loss if winter conditions exceed what the soil provides.

Publication Type

Journal Article

Full Citation

Horiza, H., Azhar, M., & Efendi, J. (2017). Ekstraksi dan karakterisasi inulin dari umbi dahlia (Dahlia sp. L) segar dan disimpan [Extraction and characterization of inulin from fresh and stored dahlia tubers (Dahlia sp. L)]. Eksakta: Berkala Ilmiah Bidang MIPA, 18(01), 31–39.

Study System
Dahlia tubers; comparison of fresh and stored tubers for inulin chemistry.

Experimental Context
Postharvest comparison of inulin extracted from fresh dahlia tubers versus tubers that had been stored, evaluating changes in water content, purity, and degree of polymerization.

Experimental Design
Ethanol-based extraction; AOAC moisture analysis; HPLC purity analysis; GC-based degree of polymerization assessment. Fresh and stored tuber samples compared directly.

Key Results
Inulin from stored tubers showed slightly lower water content and a lower average degree of polymerization than inulin from fresh tubers. Purity was comparable to chicory inulin in both fresh and stored samples.

Mechanistic Insight
The reduction in degree of polymerization during storage is consistent with enzymatic depolymerization of inulin, likely via inulinase activity. Longer-chain fructan polymers are progressively broken into shorter oligomers and monomers during storage.

Practical Guidance
Dahlia tubers are suitable inulin sources at both fresh and stored stages. Storage duration can be used to modulate inulin polymer length for applications where degree of polymerization matters. For growers focused on overwinter survival rather than inulin extraction, the finding implies that reserve carbohydrate chemistry is not static during storage. The fructan pool is being remodeled even under cold, quiescent conditions.

Why This Source Matters
This study provides direct dahlia evidence that inulin reserves change during storage, not just after planting. The shift in degree of polymerization is a biochemical marker of metabolic activity occurring during what growers often treat as a passive dormant period. For the broader understanding of dahlia tuber storage biology, this finding raises the question of how storage conditions, substrate, temperature, humidity, and duration interact with the rate and extent of fructan remodeling, and what that means for tuber vigor at planting.

Publication Type
Peer-Reviewed Journal Article

Full Citation
Cantor, M., Buta, E., Gocan, T., & Crișan, I. (2016). Influence of cultivar and planting material on soluble dry matter content of dahlia tuberous roots. Bulletin of the University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Horticulture, 73(2).

Study System
Dahlia hybrida cactus-type cultivars grown under forced and unforced tuberous root treatments.

Experimental Context
Field evaluation of cultivar and planting material effects on soluble dry matter content at harvest.

Experimental Design
Completely randomized block design with seven cultivars and two planting material types and three replications. Soluble dry matter was measured by refractometer. Duncan test and linear regression were applied.

Key Results
Soluble dry matter ranged from 11.63% to 25.47% at harvest. Highest values were recorded for ‘Star Favourite’ with forced material, ‘Tsuki Yori No Sisha’ with both forced and unforced material, and ‘Kennemerland’ with unforced material. Shoot number was not significantly correlated with soluble dry matter. Tuber weight showed a positive but mostly non-significant relationship with soluble dry matter.

Mechanistic Insight
Soluble dry matter in dahlia tuberous roots reflects inulin-rich reserves. Forcing modifies reserve dynamics in a cultivar-dependent manner, indicating that the reserve chemistry entering storage is shaped by the production history of the planting material, not only by cultivar genetics.

Practical Guidance
Cultivar and planting material combination both affect the reserve content of tuberous roots at harvest. Forcing is beneficial for reserve accumulation in some cultivars but not universally.

Why This Source Matters
This study is included as pre-storage reserve context rather than as a storage-response source. It establishes that the soluble dry matter, and by implication the inulin reserve, a tuber carries into winter storage varies substantially by cultivar and production history. That variation is the starting condition for everything that follows in storage: reserve depletion, dormancy progression, and spring vigor. Growers selecting planting material or cultivars for challenging overwintering conditions may find it useful to consider reserve content at harvest as a factor alongside other selection criteria.

The Knowledge Card summaries in this collection were written by the author based on direct reading of the cited sources. AI tools assisted with retrieval, formatting, and assembly of this collection from the Dahlia Doctor research archive. All curatorial decisions, including source selection, topic organization, and editorial framing, were made by the author.