Propagating Mulberry: Best Practices for Nursery Establishment

Mulberry (Morus spp.) is the backbone of the sericulture industry – it is the sole food source for the silkworm (Bombyx mori). The quality of silk produced depends directly on the quality and quantity of mulberry leaves available. That’s why getting the propagation and nursery establishment right is so critical. In this post, we’ll walk through the most effective methods of multiplying mulberry plants – stem cuttings, grafting, and layering – along with step-by-step nursery preparation practices that ensure healthy, uniform saplings ready for transplanting.

Why asexual propagation is preferred for mulberry 🔗

Mulberry can technically be propagated through seeds, but seed propagation introduces significant genetic variation in the offspring. This variability is undesirable in commercial sericulture, where consistency in leaf yield, quality, and disease resistance matters enormously. Asexual or vegetative propagation – using methods like cuttings, grafting, and layering – produces plants that are genetically identical to the parent. This guarantees that the desirable traits of a selected variety are faithfully passed on to every new plant.

Among the asexual methods, stem cutting propagation is by far the most widely practiced, particularly in tropical regions of India. It is simple, cost-effective, and delivers a high survival rate when done correctly. Grafting and layering serve as important alternatives for varieties that are difficult to root from cuttings.

Stem cutting propagation 🔗

Stem cuttings are the go-to method for multiplying mulberry, especially in South India, where popular varieties like V1, S36, and M5 root readily. The method works because mulberry stems have a strong natural ability to produce adventitious roots from their nodes when placed in suitable soil conditions.

Selecting and preparing the cuttings 🔗

The first step is choosing the right source material. Cuttings should come from well-matured shoots that are 6-8 months old and about 1-1.5 cm in diameter. The ideal cutting length is 15-20 cm, and each cutting must have 3-4 healthy, active buds. Select only disease-free stems from high-yielding mother plants. Avoid very thin or very thick shoots, as they tend to have poor rooting success.

When preparing the cuttings, make a clean, slanting cut at the base just below a node. This increases the surface area exposed to soil moisture and encourages root initiation. Remove any side shoots or leaves from the lower portion of the cutting.

Role of plant growth regulators 🔗

While many commercial mulberry varieties root well on their own, treating the base of cuttings with Indole-3-butyric acid (IBA) can significantly boost rooting. Research has shown that IBA application increases root number, root length, and overall survival rate. Concentrations ranging from 1000 to 5000 ppm are commonly used, depending on the variety and local conditions. Dipping the basal end of the cutting in the IBA solution for a few seconds before planting is typically sufficient.

Factors affecting rooting success 🔗

Not all mulberry varieties root equally well. The success of stem cutting propagation depends on the genotype, environmental conditions, and physiological state of the cutting material. Tropical varieties generally have higher rooting percentages compared to temperate species. Using middle portions of juvenile twigs – rather than very old or very young wood – helps maintain an optimal carbon-to-nitrogen ratio, which favours root formation. Timing also matters: cuttings prepared during the monsoon season (June-September) tend to establish faster due to favourable moisture and temperature.

Grafting methods for difficult-to-root varieties 🔗

Some mulberry cultivars – particularly several temperate species and certain improved varieties – have a low rooting potential from stem cuttings. For these, grafting is the preferred propagation technique. Grafting involves joining a shoot or bud (scion) from the desired variety onto the root system (rootstock) of a compatible, well-rooted mulberry plant. This allows farmers to exploit the root vigour of one variety while growing the foliage of another.

Root grafting 🔗

In root grafting, a scion – a young shoot or twig from the desired variety – is joined directly onto the rootstock of a compatible mulberry plant. The scion and rootstock are carefully aligned so that the cambium layers of both pieces are in contact. The graft union is then tightly secured with grafting tape or wax to prevent drying and promote healing. This method works well when strong rootstock material is available.

Bud grafting 🔗

Bud grafting uses a single vegetative bud from the desired cultivar. A small incision (typically a T-shaped or chip-bud cut) is made in the bark of the rootstock, and the bud is carefully inserted and wrapped with grafting tape. Studies on black mulberry have found that chip budding is among the most successful budding methods, with bud take rates exceeding 70% under optimal conditions. The timing of bud grafting is important – performing it during active growth periods (typically spring) yields the best results.

Shoot grafting 🔗

In shoot grafting, a longer shoot from the target variety is grafted onto the rootstock. The shoot is aligned with the rootstock, ensuring cambial contact on at least one side, and the union is bound firmly. Common techniques used include cleft grafting and whip-and-tongue grafting. Shoot grafting is especially useful when multiple varieties need to be maintained on a single rootstock for conservation or evaluation purposes.

Across all grafting methods, the biggest risk is the graft drying out before the union heals. This is why tight wrapping with parafilm or grafting tape, and sometimes the application of tree sealing wax, is essential. Grafted plants typically need to be maintained in a protected nursery environment until the graft union is well established.

Layering as a propagation method 🔗

Layering is a more labour-intensive approach to mulberry propagation, but it serves an important role for varieties that neither root well from cuttings nor respond well to grafting. In layering, a portion of a living stem is encouraged to develop roots while still attached to the parent plant. Once roots are established, the new plant is separated and transplanted.

Simple layering 🔗

This involves bending a low-growing branch down to the ground and burying a section of it under a few centimetres of moist soil. The buried portion – ideally near a node – develops adventitious roots over several weeks. Once the root system is well developed, the rooted section is cut from the parent plant and transplanted to the nursery or main field.

Air layering 🔗

Air layering (also called marcotting) is useful when it is not practical to bend branches to the ground. A ring of bark is removed (girdled) from a healthy stem, and the exposed area is wrapped with moist sphagnum moss and covered with plastic film. The girdling interrupts the downward flow of nutrients and hormones, causing roots to develop at the wound site. Once a healthy root ball forms – usually within 6-8 weeks – the branch is cut below the roots and planted.

Mound layering 🔗

In mound layering, soil is heaped around the base of a young mulberry plant to cover the lower portions of its shoots. The buried shoot bases produce roots, and each rooted shoot can later be separated as an individual plant. This method can produce multiple plants from a single parent, but it is less commonly used due to the effort involved in mounding and maintaining the soil.

Although layering gives a high success rate per plant, its scalability is limited compared to stem cuttings. It is best suited for small-scale multiplication of elite varieties or hard-to-propagate genotypes.

Preparing the mulberry nursery 🔗

A well-prepared nursery is the foundation for producing healthy, vigorous saplings. Whether you’re propagating through cuttings or transplanting grafted material, the nursery site and beds need careful attention.

Site selection and soil preparation 🔗

Choose a nursery site with well-drained, loamy to clayey loam soil that receives adequate sunlight. Avoid waterlogged areas, saline or alkaline soils, and land near factories or highways. The ideal soil pH for mulberry is 6.2 to 6.8. If the soil is too acidic, lime should be applied; for alkaline soils, gypsum is used to bring the pH into the optimal range.

The land should be deep-ploughed to a depth of 30-40 cm to break up compacted layers and improve aeration. After ploughing, cross-plough the field to bring the soil to a fine tilth. Weeds and stones should be removed during this stage. Apply well-decomposed farmyard manure (FYM) at approximately 15 kg per bed and mix it thoroughly into the soil. For heavy clay soils, adding some river sand improves drainage and friability; for sandy soils, adding tank silt or extra organic matter boosts water-holding capacity.

Creating raised nursery beds 🔗

Standard nursery beds are prepared with dimensions of 5 m × 1.5 m. Raised beds are preferred because they prevent waterlogging and promote good root development. Beds should be raised 15-20 cm above ground level, with pathways of about 30-45 cm between adjacent beds for easy access and maintenance.

Level the surface of each bed to ensure uniform water distribution during irrigation.

Planting the cuttings in the nursery 🔗

Once the beds are ready, the cuttings are planted at a spacing of 15 cm between rows and 8-10 cm between cuttings within a row. The entire length of the cutting is pushed into the soil at a slight angle, with only one bud left exposed above the ground. Press the soil firmly around each cutting to eliminate air pockets and ensure good soil-to-stem contact.

Water the nursery immediately after planting. During dry periods, irrigate once a week to keep the soil consistently moist but not waterlogged. Mulching with dried mulberry twigs or thatch helps retain moisture and suppress weeds.

Nursery maintenance and sapling care 🔗

After planting, consistent maintenance determines the quality of saplings you’ll get 3-4 months later.

Irrigation and weed management 🔗

Regular watering – typically twice a week during the initial establishment phase – is essential. Over-watering can lead to fungal diseases and root rot, so adjust the frequency based on weather and soil type. Keep the nursery beds weed-free at all times, as weeds compete aggressively with young saplings for nutrients and water. Manual weeding is the most common approach in mulberry nurseries.

Fertiliser application 🔗

Once the cuttings have sprouted and the root system is reasonably established (typically 5-6 weeks after planting), apply a balanced fertiliser. A dose of 25:25:25 kg per hectare of N:P:K is commonly recommended at this stage. The fertiliser can be dissolved in irrigation water for even distribution. For individual beds, about 500 g of ammonium sulphate or 250 g of urea dissolved in water can be applied per bed after 55-60 days of growth.

Pest and disease management 🔗

Monitor the nursery regularly for signs of common mulberry pests and diseases. Tukra (caused by the mealy bug Maconellicoccus hirsutus) and powdery mildew are among the most common nursery-stage problems. Timely spraying with appropriate treatments helps keep these issues in check. Choosing resistant or tolerant varieties like V1, which shows relative tolerance to tukra, can also reduce pest pressure in the nursery.

Allowing only one shoot per cutting 🔗

Multiple shoots may sprout from a single cutting. To ensure that each sapling develops a strong, well-formed stem, retain only the most vigorous shoot and remove the rest. This directs all the plant’s energy into producing one healthy sapling rather than several weak ones.

Transplanting saplings to the main field 🔗

Saplings are typically ready for transplanting 80-90 days (about 3-4 months) after planting the cuttings. Before uprooting, water the nursery beds thoroughly so the soil is soft and the roots come out intact. Uproot carefully using a spade or pick-axe to minimise root damage.

Trim the shoots to reduce water loss through transpiration, and trim bent or damaged roots before planting. Transplanting should ideally be done early in the morning, late evening, or on cloudy days to reduce transplant shock. The best season for transplanting in India is during the monsoon (June-September), when natural moisture supports rapid establishment.

In the main field, a plant spacing of 90 × 90 cm is commonly recommended, though this can vary depending on soil type, variety, and whether the plantation is irrigated or rainfed. Two cuttings per pit may be used for direct planting, with pits of about 30 cm³ dug and filled with a 1:2 mixture of FYM and soil.

Quick comparison of mulberry propagation methods 🔗

Stem cuttings are best for high-rooting varieties, offering the simplest, most cost-effective approach with high survival rates. Grafting is the method of choice for varieties that root poorly, allowing farmers to combine the root strength of one variety with the leaf quality of another – though it requires more technical skill. Layering is reserved for varieties that respond poorly to both cuttings and grafting; it gives reliable results per plant but is labour-intensive and hard to scale. In commercial sericulture, stem cuttings remain dominant, with grafting used as a targeted solution for specific cultivars.

What do you think? If you’re planning a mulberry garden, which propagation method would best suit the varieties available in your region? And how do you think using plant growth regulators like IBA could change the economics of nursery operations for small-scale sericulture farmers?

References

1. https://www.fao.org/4/x9895E/x9895e04.htm
2. http://troindia.in/journal/ijcesr/vol5iss2part3/61-68.pdf
3. https://www.researchgate.net/publication/375497073_Mulberry_cutting_propagation_A_Review
4. https://bnrc.springeropen.com/articles/10.1186/s42269-020-00314-y
5. https://www.researchgate.net/publication/289472950_Effect_of_graftingbudding_techniques_and_time_on_propagation_of_black_mulberry_Morus_nigra_L_in_cold_temperate_zones
6. https://silks.csb.gov.in/panchkula/mulberry-crop-production-technology/
7. https://www.infonet-biovision.org/fodder-production/mulberry-trees