Custard Apple Nursery and Grafting: Producing Quality Planting Material

Research published by IIHR Bangalore and ICAR-NRC for Arid Horticulture documents that the method of plant propagation used for custard apple has profound consequences for orchard productivity, fruit quality consistency, and time to first commercial bearing. Seedling-grown custard apple trees exhibit high variability in fruit size, sweetness, seed count, and skin characteristics even within the same variety due to genetic segregation during sexual reproduction, making orchard quality standardisation impossible with seedling planting material. Grafted plants produced by approach grafting or epicotyl grafting using scions from selected high-yielding mother trees begin bearing commercial fruit one to two years earlier than seedlings, produce uniform fruit quality that matches the mother variety precisely, and achieve field establishment survival rates of 85 to 95 percent in ICAR trials compared to 60 to 70 percent for bareroot seedling transplants. Understanding nursery production and grafting techniques allows progressive farmers to produce their own quality planting material and reduce establishment costs significantly.

Rootstock Selection and Seedling Preparation

ICAR-NRCAH research on custard apple rootstock selection documents that wild custard apple, Annona reticulata, also called bullock's heart or ramphal, is the most widely used and research-validated rootstock for commercial custard apple grafting in India due to its vigorous root system, adaptation to a wide range of soil types including heavier black cotton soils where pure Annona squamosa struggles, and strong compatibility with all major commercial custard apple varieties. Rootstock seeds are collected from fully ripe Annona reticulata fruits, washed, dried in shade for 3 to 5 days, and sown directly in nursery beds or polythene bags filled with a mixture of red soil, sand, and farmyard manure in equal proportions. Germination occurs within 21 to 30 days at soil temperatures above 25 degrees Celsius. Seedlings are grown in nursery bags for 6 to 8 months until stem diameter at the grafting point reaches 8 to 12 mm, which is the optimal size for approach grafting documented in IIHR research.

Approach Grafting: The Most Reliable Custard Apple Propagation Method

Approach grafting, also called inarching, is documented by IIHR Bangalore as the most reliable propagation method for custard apple achieving success rates of 75 to 90 percent in skilled hands, significantly higher than other grafting methods. The technique requires that the rootstock plant in its nursery bag be physically brought close to a selected scion branch still attached to the mother tree. A 3 to 5 cm long and 1.5 to 2 cm wide slice of bark and wood is removed from both the rootstock stem and the scion branch at matching positions. The two cut surfaces are placed in firm contact, bound tightly with polythene grafting tape, and held in position. Union formation occurs within 45 to 60 days when the cambial tissues of rootstock and scion grow together. After confirming union by gently testing for resistance to separation, the scion is severed from the mother tree below the union point and the rootstock top is removed above the union, leaving the grafted plant as an independent unit ready for hardening and field transplanting. Best results are obtained when approach grafting is done between February and April or between August and October according to IIHR seasonal grafting trials.

Epicotyl Grafting: Faster and More Scalable

Epicotyl grafting, a technique developed and validated at IIHR Bangalore specifically for Annona species, allows grafting onto very young rootstock seedlings at the epicotyl stage just 15 to 25 days after seed germination, dramatically reducing the nursery period compared to approach grafting which requires 6 to 8 months of rootstock growth. In epicotyl grafting, the germinated seedling is decapitated at 5 to 7 cm above the soil surface, a vertical cleft of 1.5 to 2 cm depth is made in the remaining stem, and a wedge-shaped scion of 5 to 8 cm length with 2 to 3 nodes prepared from semi-hardwood shoots of the desired mother variety is inserted into the cleft and bound with polythene tape. The entire grafted unit is covered with a transparent polythene bag to maintain humidity during the union period of 15 to 21 days. IIHR research documents epicotyl grafting success rates of 70 to 85 percent with skilled operators and total nursery-to-field-ready plant time of only 3 to 4 months compared to 10 to 12 months for approach grafting, making it the preferred method for large-scale commercial nursery production.

Selecting and Managing Scion Mother Trees

The quality of grafted planting material is entirely determined by the quality of the mother tree from which scion wood is collected, making mother tree selection and management the most critical decision in custard apple nursery production. ICAR guidelines for mother tree selection specify minimum criteria of consistent production above 80 kg of marketable fruit per tree per season for at least three consecutive years, fruit weight above 250 grams for standard varieties and above 350 grams for premium varieties, pulp percentage above 65 percent of total fruit weight, total soluble solids above 22 degrees Brix indicating high sweetness, and freedom from any symptoms of viral, bacterial, or fungal disease. Selected mother trees should be tagged with permanent labels and maintained under optimal nutrition and irrigation to ensure continuous availability of healthy semi-hardwood scion shoots. Scion shoots selected for grafting should be from the current season's growth, 8 to 12 mm in diameter, with at least 3 to 4 plump dormant buds, and collected in the early morning hours to maintain maximum tissue turgidity.

Nursery Management and Hardening Before Field Planting

Research from Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth documents that inadequate hardening of nursery-raised custard apple grafts before field transplanting is one of the most common causes of high post-transplanting mortality in farmer orchards. Grafted plants maintained in nursery shade house conditions with 50 percent shade net covering and regular irrigation must be progressively hardened over 4 to 6 weeks before field planting by gradually reducing shade net coverage and irrigation frequency to accustom plants to full sun and reduced water availability conditions similar to field conditions. During the nursery period after graft union confirmation, plants should receive weekly foliar application of 0.5 percent NPK 19:19:19 water-soluble fertiliser to build root volume and canopy before transplanting. Plants are ready for field transplanting when they have developed a minimum of 4 to 6 new leaves beyond the graft union, have a well-developed root ball filling the nursery bag completely, and show no signs of disease or pest infestation. Field transplanting should be done at the onset of monsoon in June or July when soil moisture ensures establishment without supplemental irrigation.