Best Practices for Selecting and Grafting Cashew Planting Materials

Cashew (Anacardium occidentale L.) is a highly cross-pollinated crop, and that single biological fact shapes every decision around how to grow it commercially. Because cashew trees don’t breed true from seed, farmers who simply collect and sow nuts from their best trees have no guarantee the resulting plants will inherit those desirable traits. This is why the choice of planting material – whether seedlings or vegetatively propagated grafts – is one of the most consequential decisions in cashew production. Getting it right from the start sets the foundation for yield, quality, and profitability for decades ahead.

Two main routes: seed propagation vs. vegetative propagation 🔗

Cashew can be propagated either sexually through seeds or asexually through vegetative methods. Seed propagation is the oldest and simplest approach – seeds are sown directly and allowed to germinate. It requires minimal skill, is relatively inexpensive, and suits small-scale farmers in areas where grafted planting material is unavailable. However, because cashew is predominantly cross-pollinated, seedling progenies show wide variation in growth, yielding ability, nut characters, and quality parameters. In practical terms, a seedling from a high-yielding mother tree may produce an underperforming tree – or a completely different nut size and quality than expected.

Vegetative propagation solves this problem by preserving the exact genetic makeup of a selected superior plant. All cashew research institutions today recommend vegetatively propagated planting material for commercial orchards. Plants grown from raw nuts should not be used as planting material for commercial production, as the resulting genetic variability undermines orchard consistency and yield predictability.

Selecting the right mother plant for seed propagation 🔗

When seedlings are used – typically as rootstock for grafting rather than as the final fruiting tree – seed source still matters significantly. Seeds should be collected from well-selected mother plants with specific agronomic qualities. According to standard nursery management criteria, desirable mother plant traits include a high yield of 15-20 kg nuts per tree at 12-15 years of age, medium nut size with a high shelling percentage of 26-30%, a regular bearing habit, a dwarf and bushy plant type with compact canopy, a high proportion of hermaphrodite flowers per panicle, good fruit set with minimal premature nut fall, and adequate resistance to pests and diseases.

Seed viability is also time-sensitive. Fresh cashew seeds have a germination capacity of over 80%, which declines by about 20% within 6-8 months and is completely lost by 14 months. Seeds are ideally collected during peak harvest, separated from the cashew apple, thoroughly cleaned, and sun-dried for at least 16 hours before storage or sowing.

Development of high-yielding varieties through selective breeding 🔗

The genetic improvement of cashew has been an active area of research globally. In India, 63 high-yielding varieties have been released for commercial cultivation by the ICAR-Directorate of Cashew Research (DCR) and various agricultural universities. These varieties have emerged through systematic programs involving germplasm collection, evaluation of wild and cultivated accessions, and targeted crossing of selected parents.

Breeding strategies include direct selection from superior seedling populations and controlled hybridization. Some well-known released varieties include NRCC Selection-1, NRCC Selection-2, Bhaskara, Ullal-1, Ullal-3, VRI-3, and the hybrid H-130, developed at ICAR-DCR Puttur as a cross between NRCC Sel-2 and Bedasi – a high-yielding, bold-nut hybrid suited for high-density planting. Variety performance, however, varies significantly by region, meaning regional suitability must be assessed before selecting a variety for a specific location.

A multi-location stability study across major cashew-growing zones in India found that varieties like K-22-1 and Bhubaneswar-1 showed stable yield performance across diverse environments – an important criterion when recommending planting material for farmers operating in variable agro-climatic conditions.

Why softwood grafting is the preferred commercial method 🔗

Among all vegetative propagation techniques tested in cashew – including air layering, budding, epicotyl grafting, and cuttings – softwood grafting has emerged as the most effective and commercially scalable method. It involves joining a scion (a shoot taken from a proven high-yielding variety) with a young seedling rootstock, creating a plant that combines the superior fruiting traits of the scion with the hardy, well-anchored root system of the rootstock.

Softwood grafting is the most suitable propagation method for large-scale multiplication of clonal cashew plants of high-yielding varieties, and it has had a major impact on increasing cashew productivity in producing countries including India, Ghana, Sri Lanka, and West African nations.

Advantages over other propagation methods 🔗

Air layering was once a popular alternative but has largely been abandoned for commercial use. Although it can achieve reasonable rooting success, air-layered plants typically develop poor tap root formation, resulting in weak anchorage and increased susceptibility to cyclonic winds and drought stress. Epicotyl grafting – which uses very young seedlings (10-15 days old) as rootstock – achieves only 15-30% recovery of transferable grafts and is not suitable for large-scale nurseries. Softwood grafting, by contrast, delivers consistently higher success rates and is far more suited to nursery production at scale.

Step-by-step process of softwood grafting in cashew 🔗

Softwood grafting uses seedlings that are 45-60 days old as rootstocks. The terminal portion of the rootstock stem is removed 15-20 cm above the ground, and all leaves except those in the first two whorls are stripped off. A 3-4 cm longitudinal cleft is made at the centre of the cut stem. The scion – a shoot taken from a proven mother tree – is trimmed to about 10 cm in length with its lower end shaped into a “V” or wedge form, then carefully inserted into the cleft with the cambial layers of both rootstock and scion aligned.

Proper alignment of the cambium is critical: this is the actively dividing tissue layer that forms the graft union. Misalignment is a primary reason for graft failure. Once inserted, the union is firmly wrapped with a grafting tape or polythene strip to hold the scion in place and prevent desiccation.

Scion preparation: pre-curing 🔗

Scions are not taken fresh and grafted immediately. They undergo a process called pre-curing (also called scion hardening), where the selected shoot from the mother tree is defoliated 7-10 days before grafting. This process reduces transpiration from the scion after grafting and improves the chances of successful union formation. Scions should be sourced only from known high-yielding, disease-free mother trees that have been verified for superior performance over multiple seasons.

Post-grafting care and success factors 🔗

After grafting, the scion including the union is covered with a narrow polythene cap (approximately 1.5 × 10 cm) and placed in a propagator maintained at around 38°C, 90% relative humidity, and 40% light intensity under a net house. Research showed that covering softwood grafts with polythene caps and placing them in a propagator under a net house achieved sprouting rates as high as 88%. The polythene cap is removed after sprouting and before the leaves fully open; the grafting strip is removed after about three months.

A study on cashew softwood grafting in Ghana found that retaining four mature basal leaves on 60-day-old rootstocks significantly improved graft union success, while rootstocks with no basal leaves recorded much lower success rates. The same study identified July as the most suitable month for grafting in canopy substitution operations. Grafted plants are generally ready for field planting within 2.5 to 3.5 months of grafting.

Seedlings as rootstock: their continued importance 🔗

Even in a grafting-dominated system, seedlings play an indispensable role – as rootstocks. Seed propagation in cashew is now primarily practiced to raise rootstock material rather than for producing fruiting trees directly. For rootstock use, seeds are collected between March and May; heavy, well-filled nuts that sink in water are selected and mixed with fine sand for storage. They typically germinate within 15-20 days under nursery conditions.

A related application of grafting onto existing trees is called top working – a rejuvenation technique for old, low-yielding seedling orchards. Trees that are 20-25 years old are cut back to 0.5 m from the ground during December-February, allowed to sprout new shoots, and those shoots are then softwood grafted (cleft grafted) at 40-50 days of age with scions from improved clones. Top-worked trees, backed by their mature root systems, have been reported to yield around 4 kg per tree from the second year after rejuvenation.

Grafted plants vs. seedling trees: key differences in the field 🔗

The practical advantages of grafted planting material over seedling-raised trees are well documented. Grafted plants start bearing fruit within 2-4 years of field planting, compared to 5-7 years for seedling trees. They produce uniform crops with consistent nut size and quality, and deliver the yield characteristics of the selected scion variety reliably throughout their productive life. The FAO’s guidelines on cashew farm establishment recommend grafted plants as the preferred planting material for commercial operations, with planting ideally carried out at the onset of the monsoon season, from June through mid-July, to ensure adequate soil moisture for establishment.

While grafted plants carry a higher nursery cost than seedlings, the investment pays off through earlier and more consistent production. For farmers transitioning from subsistence-level cashew growing to commercial operations, adopting certified grafted material from approved varieties is the single most impactful agronomic decision they can make.

What do you think? Given that most existing cashew plantations in many regions are still composed of unselected seedling trees, what would it take – in terms of policy support, nursery infrastructure, or farmer training – to accelerate the adoption of certified grafted planting material at scale? And with over 60 improved varieties now available in India alone, how should farmers approach variety selection when performance differs so significantly across regions?

References

1. https://www.slideshare.net/slideshow/cashew-propagation-and-nursery-management/263520415
2. https://www.agrifarming.in/top-20-steps-to-boost-cashew-yield-how-to-increase-production-cashew-size-and-quality
3. https://link.springer.com/chapter/10.1007/978-981-97-5940-8_11
4. https://cashew.icar.gov.in/success-stories/
5. https://www.nature.com/articles/s41598-024-52030-6
6. https://doi.org/10.22271/09746315.2022.v18.i2.1568
7. https://www.ccsenet.org/journal/index.php/jas/article/view/0/43279
8. https://indiaagronet.com/horticulture/CONTENTS/cashew.htm
9. https://openknowledge.fao.org/server/api/core/bitstreams/385ac9b1-d920-40ae-bb10-6bb42f50a348/content