Rootstocks are the foundation of a successful fruit tree nursery. They form the lower part of a grafted tree and determine the plant’s strength, disease resistance, and adaptability to local soil conditions.

For nursery operators in Kenya, learning how to raise strong rootstocks is essential for producing high-quality grafted seedlings of avocado, mango, citrus, and other fruit trees.

This Standard Operating Procedure (SOP) explains how beginners can raise healthy fruit tree rootstocks step by step.

What Is a Rootstock?

A rootstock is the seedling that provides the root system and lower stem of a grafted fruit tree.

After growing the rootstock, a farmer grafts a scion (cutting from a desirable fruit variety) onto it.

Benefits of using rootstocks:

• Strong root system
• Better disease resistance
• Improved adaptability to soil conditions
• Uniform orchard performance

Fruit Trees That Require Rootstocks

Common fruit nursery crops in Kenya that use rootstocks include:

Avocado

Mango

Citrus (orange, lemon, tangerine, pixie)

Guava

Cashew

Most nursery operators raise rootstocks from seeds of vigorous local varieties.

Tools and Materials Required

Basic Tools

• Spade or shovel
• Wheelbarrow
• Watering can
• Secateurs
• Nursery trays or seedbeds

Nursery Materials

• Polybags (4×6 or 6×9 inches)
• Topsoil
• River sand
• Well-decomposed manure
• Fruit seeds for rootstocks
• Shade net or grass shade

Ideal Nursery Conditions

A good rootstock nursery should have:

Partial shade (50%)

Reliable water supply

Well-drained soil

Protection from animals

Most small nurseries operate in backyards or small plots of 50–100 square meters.

Step-by-Step SOP for Raising Rootstocks

Step 1: Select Suitable Seeds

Choose seeds from healthy, high-yielding trees.

Examples:

Avocado – seeds from strong local trees

Mango – seeds from vigorous varieties

Citrus – seeds from disease-free fruits

Avoid:

• Rotten fruits
• Diseased trees
• Very small seeds

Healthy seeds produce vigorous rootstocks.

Step 2: Extract and Prepare Seeds

1. Remove seeds from ripe fruits.
2. Wash seeds thoroughly to remove pulp.
3. Air dry for a few hours.

Important notes:

• Do not store avocado seeds for long (they lose viability quickly).
• Plant seeds within a few days of extraction.

Step 3: Prepare the Nursery Soil

Good soil mixture improves root development.

Recommended mix:3 parts topsoil

1 part river sand

1 part well-decomposed manure

Benefits:

• Good drainage
• Rich nutrients
• Strong root growth

Fill the mixture into polybags or nursery beds.

Step 4: Establish a Seedbed (Optional)

Some nurseries first germinate seeds in seedbeds or trays.

Procedure:

1. Prepare raised beds about 1 meter wide.
2. Mix soil with manure and sand.
3. Level the surface.

Spacing in seedbed:5–10 cm between seeds

This method saves space during germination.

Step 5: Plant the Seeds

Plant seeds at the correct depth.

General rule:

Depth = about twice the size of the seed

Examples:

Avocado – half buried in soil

Mango – flat side down

Citrus – about 1–2 cm deep

After planting: Water gently.

Step 6: Provide Shade

Young seedlings are sensitive to harsh sunlight.

Provide shade using:

• Shade nets
• Dry grass thatching
• Banana leaves

Shade should allow about 50% sunlight.

Step 7: Water Regularly

Watering schedule:

• Once daily during dry weather
• Reduce watering during rainy periods

Avoid:

• Overwatering
• Waterlogging

Good drainage is important.

Step 8: Transplant Seedlings to Polybags

If seeds were started in seedbeds:

Transplant when seedlings have:3–4 true leaves

Procedure:

1. Carefully uproot seedlings with soil around roots.
2. Transfer into polybags filled with nursery soil mix.
3. Water immediately after transplanting.

This allows seedlings to develop strong root systems.

Step 9: Weed and Maintain Nursery Hygiene

Remove weeds regularly.

Weeds compete for:

• Nutrients
• Water
• Light

Maintain clean nursery conditions to reduce disease and pests.

Step 10: Fertilize if Necessary

If growth is slow, apply:

• Well-decomposed manure
• Compost

Avoid heavy chemical fertilizer at early stages.

Growth Period Before Grafting

Rootstocks are usually ready for grafting when they are:3–6 months old

Signs they are ready:

• Pencil-thick stem
• Healthy leaves
• Strong root system

At this stage they can be grafted with improved fruit varieties.

Rootstock Production Timeline

Typical timeline:

Seed planting → Germination → Seedling growth → Ready for grafting

Approximate durations:

Avocado: 2–3 months

Mango: 3–4 months

Citrus: 4–6 months

Common Rootstock Problems

Damping-off Disease

Causes seedlings to collapse.

Prevention:

• Avoid overwatering
• Use well-drained soil

Weak Seedlings

Caused by poor seeds.

Solution:

Use seeds from healthy mother trees.

Pest Attacks

Common pests:

• Aphids
• Leaf miners

Control using recommended nursery pesticides.

Tips for Producing Strong Rootstocks

Use Fresh Seeds

Old seeds often fail to germinate.

Maintain Good Soil Mix

Balanced soil promotes strong roots.

Avoid Overcrowding

Proper spacing improves seedling growth.

Maintain Consistent Watering

Seedlings should not dry out.

Label Different Fruit Types

Helps with organization during grafting.

Income Potential from Rootstock Production

Rootstocks can also be sold directly to other nurseries.

Typical prices:

Citrus rootstocks: Ksh 20 – 40

Mango rootstocks: Ksh 20 – 50

Avocado rootstocks: Ksh 30 – 60

However, grafting them increases value significantly, with grafted seedlings selling for Ksh 120 – 300.

Final Thoughts

Raising fruit tree rootstocks is a key step in running a profitable fruit tree nursery in Kenya. With a small space, basic tools, and quality seeds, beginners can produce hundreds or even thousands of rootstocks every season.

Once mastered, this skill allows nursery operators to produce grafted fruit seedlings that farmers highly demand, creating a reliable agribusiness with strong income potential.