Dissertation – Rootstock Trial

Rootstocks are widely employed in perennial crops such as grapevine and apple to improve plant vigor, resilience, productivity and fruit quality. In coffee, however, rootstock use remains uncommon. In this study, we evaluated the performance of Coffea arabica var. Typica cultivated on its own roots versus Typica grafted onto the RM009 rootstock from the year 2023-2025.


Typica is often limited by relatively low vigor, modest yields, and susceptibility to root-related stress. In many other perennial crops, grafting scion varieties onto selected rootstocks has become standard practice, addressing challenges like these. Coffee has historically been propagated by seed and planted on its own roots. While this ensures varietal purity, it does not capitalize on the potential benefits of rootstocks. This study explores whether grafting Typica onto the RM009 rootstock can improve agronomic and sensory performance through increased vitality and vigour.

Experimental Setup

Two treatments were established in parallel plots under identical environmental and agronomic conditions in our climate-controlled research station. Both treatments were cultivated next to each other, in the same climate chamber, and treated the same for the entire duration of the trial. The data in this dissertation is collected from year 4-6 since planting when the plants came into full production (year 2023-2025). The two treatments:

1. Typica (own roots): propagated from seed and planted on its own roots.

2. Typica/RM009 (grafted): Typica scions grafted onto the RM009 rootstock.
   

To get the best idea of the agronomical performance of the varieties, we investigated both the reproductive and vegetative parameters.:

• Mean shoot length (cm/yr): annual vegetative growth.

• Yield (kg green coffee/tree): average per-tree productivity.

• Seed density (g/L): a proxy for bean filling and quality.

• Cupping score: mean sensory evaluation (SCA protocol, 60–100 scale).
  

Mean shoot length of the annual shoots were measured post-harvest. All branches in the entire treatment were measured and averaged. Yield was recorded for individual trees in a treatment, combined and averaged. Seed density was measured six times per treatment with the combined harvest of the treatment. The cupping score was evaluated by a trained sensory panel.

Results

• Shoot growth: Grafted Typica produced shoots that were on average ~21% longer across three years, demonstrating consistently greater vegetative vigor.

• Yield: Grafted plants yielded ~23% more green coffee per tree, with gains consistent across years 4–6.

• Seed density: RM009 rootstock increased seed density by ~5.4%, indicating better seed filling and quality.

• Cup quality: Cupping scores were consistently higher in grafted Typica, with an average +1.3 point increase, characterized by fuller body, enhanced sweetness, and greater clarity compared to the lighter and more delicate expression of own-rooted Typica.

Benefits and implications

The data demonstrates clear and consistent benefits from grafting Typica onto the RM009 rootstock. Over the last three years, grafted trees showed improved vegetative vigor, higher yields, denser seeds, and superior sensory expression. The improvement for all parameters is likely to result from improved root system performance, facilitating greater nutrient and water uptake. These results suggest that grafting could be a powerful tool in coffee cultivation. However, the potential value of rootstocks is unlikely to be uniform across all varieties.

A lot of varieties are known for their exceptional sensory profiles but often show reduced vigor, modest yields, and increased susceptibility to environmental stress. For these varieties, grafting onto a well-adapted rootstock could provide a substantial advantage by compensating for their low vitality and weaker root systems. Enhanced nutrient uptake, water efficiency, and resilience may allow these varieties to produce more coffee and express their quality potential more consistently and with greater clarity, as was observed in this trial with Typica.


Conversely, modern high-vitality cultivars such as Catuaí, Castillo, or certain hybrids may derive less benefit from grafting. These varieties already possess robust root systems and have been selected for higher yields and resilience. In such cases, the added cost and complexity of grafting may not translate into meaningful gains, unless specific rootstocks confer unique advantages such as nematode resistance or drought tolerance.


It is also possible that certain scion–rootstock interactions could lead to incompatibilities, physiological imbalances, or unintended effects on cup quality. Therefore, the broader adoption of grafting in coffee should be guided by variety-specific evaluations. Future research should examine a wider set of scion varieties, focusing on both heritage types with low vitality and modern high-performance cultivars, to determine where grafting provides the greatest net benefit.

Summary 

These findings support the hypothesis that grafting could be a transformative practice in coffee cultivation, particularly for varieties that are prized for cup quality but limited by agronomic weakness. Grafting holds particular promise for varieties whose quality potential is limited by weak agronomic performance. For high-vitality cultivars, its role may be more specialized, targeting resilience against biotic and abiotic stresses rather than general yield or quality improvement.