Farm & Nursery Trials

Most fruit trees sold commercially are grafted onto a relatively small number of well-understood rootstocks selected for reliability, productivity and predictable growth. We use these established rootstocks throughout Tonnóg Farm and they remain the foundation of the nursery.

Alongside them, we are developing a series of long-term trials using native species, locally sourced material and seedling rootstocks. The aim is not to replace proven commercial rootstocks, but to explore how different combinations behave in productive hedgerows, orchards, food forests and future agroforestry systems under local conditions.

The approach is deliberately simple: propagate material, graft selected cultivars, plant them in different systems, measure growth and compatibility, and continue observing them over many years. Some combinations may prove useful. Others may not. Either result is valuable.

Tonnóg farm nursery beds in Autumn

Why explore native rootstocks?

Commercial rootstocks are extremely useful because they give growers a known level of vigour, precocity and compatibility.

Native and locally sourced rootstocks offer a different set of questions.

Can they integrate more naturally into hedgerows and mixed landscapes? Can they establish successfully under lower-input conditions? How much variation exists between locally raised seedlings? Can productive cultivars be incorporated into existing native tree systems without losing their ecological value?

The traits being observed include:

·       graft compatibility

·       vigour

·       establishment

·       longevity

·       adaptation to local conditions

·       sucker production

·       suitability for hedgerows and agroforestry

·       interaction with surrounding vegetation

·       eventual fruiting performance

The trials are designed to be observational and long term rather than to produce quick conclusions.

Medlar on Hawthorn (Crataegus monogyna)

Medlar on hawthorn is currently one of the strongest combinations in the trial programme.

Hawthorn is widespread throughout Irish hedgerows and is well adapted to local soils and weather. It also provides substantial habitat and food value for wildlife. Medlar has a long history of cultivation in Europe and is particularly suited to orchard, food forest and heritage planting.

At Tonnóg, medlar is being grafted onto Irish-provenance hawthorn seedlings and planted both as individual trees and within productive hedgerow systems.

The aim is to examine whether hawthorn can provide a durable native rootstock for medlar while allowing productive fruit trees to remain physically integrated with native hedge structures. Current observations include successful graft unions and healthy shoot extension. Long-term vigour, fruiting, union strength and longevity will continue to be monitored.

Medlar cleft graft on local Hawthorn (Crataegus monogyna) seedling rootstock

Pear on Hawthorn

Pear on hawthorn is one of the more experimental parts of the trial programme.

The aim is to explore whether hawthorn can support pear within productive hedgerows and mixed planting systems, rather than to replace conventional pear rootstocks.

At Tonnóg, established hawthorns will be used as long-term trial trees. Conference and Beurré Hardy will be the two principal cultivars used, allowing their compatibility, vigour and longer-term development on hawthorn to be compared under similar conditions.

The main questions are:

·       graft compatibility

·       vigour

·       long-term union strength

·       flowering and fruiting

·       response to pruning

·       suitability for productive hedgerow systems

This work remains exploratory, and conclusions will depend on performance over several years rather than initial graft success alone.

The mature hedgerows at Tonnóg farm are dominated by blackthorn and hawthorn trees. These trees will be grafted with plum/damson as well as medlar and pear cultivars in order to trial if established hedgerows can become productive food-producing hedges that retain their habitat and biodiversity value 

Damson & Plum on Blackthorn (Prunus spinosa)

Blackthorn is already an important structural species in the Irish landscape and naturally forms dense, suckering hedges.

At Tonnóg, blackthorn rootstock material is propagated from locally selected suckers and stool layers rather than from seed.

Damsons and plums are being grafted onto this material to assess their potential for productive hedgerows and boundary systems. Cultivars currently being used include Farleigh Damson and selected plums such as Belle de Louvain, Mirabelle de Nancy and Czar.

The main questions are:

·       graft compatibility

·       vigour

·       sucker behaviour

·       fruiting

·       long-term stability

·       management within a hedge rather than an orchard

Blackthorn may never offer the predictability of St. Julien A, which remains an important commercial plum rootstock in the nursery, but it may prove useful in situations where resilience, hedgerow integration and local adaptation are more important than uniformity.

Cherry on Wild Cherry (Prunus avium)

Wild cherry is the native ancestor of cultivated sweet cherries and can produce large, long-lived trees. Commercial cherry rootstocks are often selected to control size and encourage early fruiting. Wild cherry represents a different approach.

At Tonnóg, cultivated cherries are being grafted onto Irish-provenance wild cherry seedlings and planted where greater vigour is acceptable. Cultivars include Stella, Sunburst and Morello.

The trial is examining:

·       compatibility

·       vigour

·       establishment

·       tree form

·       long-term support requirements

·       suitability for orchard, hedgerow and agroforestry planting

The expectation is not for compact orchard trees, but potentially larger, more structurally independent trees suited to less intensive systems or silvopastoral/silvoarable agroforestry.

Aronia on Rowan (Sorbus aucuparia)

Aronia on rowan remains one of the more experimental combinations in the nursery.

Rowan is a familiar native tree with good landscape and biodiversity value, while aronia provides edible fruit and compact growth. Initial grafting results have been mixed, which is exactly why the trial is useful. Some grafts have established strongly, some have shown moderate development and others have failed.

The important questions now are not simply whether a graft survives its first season, but whether unions remain healthy over several years and whether the rootstock and scion remain compatible as both increase in diameter.

Cultivars under evaluation include Viking and Galicjanka.

Aronia cultivars grafted onto seedling Rowan (Sorbus aucuparia) seedling rootstocks back in Spring

Apple on Irish-provenance Crab Apple (Malus sylvestris)

The apple work is becoming one of the more systematic parts of the project.

Irish-provenance crab apple seedlings are being used as genetically variable rootstocks for heritage apple cultivars. Unlike clonal commercial rootstocks such as M26 or MM106, each seedling is genetically different. That variability is normally something commercial nurseries try to avoid. In this trial, it is part of what we want to observe.

The aim is to compare growth and vigour of the same apple cultivars across different seedling rootstocks and planting systems.

For each cultivar, several trees will be established in contrasting situations, including:

·       hedgerow

·       orchard

·       mixed agroforestry planting

The trial is primarily observational.

Measurements will include annual extension growth, overall vigour, establishment and eventually flowering and fruiting. By growing the same cultivar on different crab seedlings and in different systems, it should become possible to separate some of the effects of rootstock variation from those of site and management.

The purpose is not to identify a single ‘best’ crab apple rootstock quickly, but to build a long-term record of how locally sourced seedling material behaves. Over time, particularly strong or useful individuals may be selected for further propagation and evaluation.

Irish heritage apple cultivars grafted onto local Crab apple (Malus sylvestris) seedling rootstocks

A native rootstock orchard and productive hedgerows

A major part of the work is moving these combinations out of the propagation tunnel and into permanent planting systems.

The native-rootstock orchard and associated hedgerows will include combinations such as:

·       apples on crab apple

·       medlar on hawthorn

·       pear on hawthorn

·       damson on blackthorn

·       cherry on wild cherry

·       aronia on rowan

This allows the trees to be evaluated not only as grafts, but as parts of real planting systems. A graft that survives in a nursery bed may behave very differently after ten years in a hedge, orchard or mixed agroforestry planting. The farm therefore becomes the long-term trial site for the nursery.

Commercial rootstocks are still vitally important

None of this work changes the role of established commercial rootstocks.

M26, MM106, Quince A, St. Julien A, Colt and other proven stocks remain essential where predictable tree size, cropping and management are required. They will continue to form the core of standard nursery production.

The native and alternative rootstock programme sits alongside them. It is intended for situations where landscape integration, genetic diversity, local provenance or long-term resilience may be as important as uniformity.

Hazel, chestnut and other productive tree crops

Hazel and sweet chestnut remain important crops at Tonnóg, but they now sit outside the rootstock trial programme. The focus with both species is nut production, propagation and development of productive perennial systems.

Hazel is being evaluated through orchard performance and vegetative propagation, while chestnut is being developed primarily as a nut crop and as seedling nursery stock.

These species remain central to the wider idea of perennial food production, but are better treated as productive tree crops in their own right rather than as part of the grafting trial work.

Looking ahead

These trials are deliberately long term.

Compatibility cannot be judged from a successful graft union in the first year. Vigour, structural strength, fruiting, root behaviour and resilience may take many years to understand properly. That is why the project is being built around permanent trial plantings rather than short nursery observations. Some combinations may eventually become useful nursery products. Others may remain experimental. Some will probably fail.

The important part is building a record of what actually happens under Irish conditions.

Commercial rootstocks give us predictability.

Native and locally sourced material gives us variation. Some of that genetic variation, together with any useful local adaptation that emerges through long-term observation, may become increasingly valuable as a changing climate exposes fruit trees to more variable and extreme growing conditions.

The other interesting question is whether some of that variation can be useful in the development of productive hedgerows, orchards and agroforestry systems that are better integrated into the wider landscape.

That is what these trials intend to find out.