Propagation Techniques: Mastering Cuttings and Runners

The Science of Vegetative Propagation

Vegetative propagation is essentially cloning. When you plant a seed, the resulting plant can vary slightly from its parent. But when you take a cutting from a strong, highly aromatic, disease-resistant rosemary bush, the new plant will be an exact genetic clone of that mother plant, carrying the exact same high-quality aroma, growth rate, and flavor.

There are two primary methods of vegetative propagation for herbs:

Stem Cuttings (For Woody Herbs like Rosemary and Thyme): Taking a healthy branch, removing the lower leaves, and encouraging it to grow new roots in water or a moist medium.
Runners and Slips (For Spreading Herbs like Mint and Lemongrass): Splitting apart the underground root systems or vines of established plants to create multiple new, independent plants.

       [Rosemary Stem Cutting Step-by-Step]
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       1. Cut a 10-15cm semi-hardwood stem.
       2. Strip leaves from the bottom 5cm.
       3. Insert stripped stem into moist sandy medium or water.
       4. In 2-3 weeks, roots emerge! Transplant to field.

Step-by-Step: Mastering Stem Cuttings (Rosemary & Thyme)

Select the Mother Plant: Choose a vigorous, mature, disease-free rosemary or thyme bush.
Cut: Using sharp, clean pruning shears or a razor blade, cut a $10\text{-}15\text{cm}$ stem from the current season’s growth. Choose a stem that is green at the top but starting to turn woody/brown at the base (known as semi-hardwood).
Strip: Gently strip off all the leaves from the bottom $5\text{cm}$ of the cutting. This is where the roots will emerge, and leaves left underground will simply rot.
Prepare the Medium: Fill propagation trays or small plastic bags with a highly draining mix of 2 parts clean river sand and 1 part well-cured compost (no heavy soil!).
Insert and Water: Dip the bottom of the stem in clean water, insert it $5\text{cm}$ deep into the sandy medium, and press the medium firmly around it. Water daily to keep the sand consistently moist but not soggy. Keep the cuttings under your shade structure. Roots will develop in 3 to 4 weeks, and the plant can be transplanted to the field in 6 to 8 weeks.

Step-by-Step: Mastering Runners and Slips (Mint & Lemongrass)

Mint Runners: Mint spreads naturally by sending out long horizontal vines across the ground (runners) that grow roots wherever they touch the soil. To propagate, simply dig up a section of these rooted runners, cut them into $10\text{cm}$ pieces (each containing at least two root joints), and plant them directly into your new moist beds.
Lemongrass Slips: Lemongrass grows in thick, dense clumps of multiple stalks (slips). To propagate, dig up an entire mature clump. Shake off the soil, and gently pull the individual stalks apart. Cut the leafy tops down to about $15\text{cm}$ and trim the roots slightly. Plant these individual “slips” directly into the soil – they will rapidly grow into new, massive clumps.

Local Case Study: Joyce’s Free Rosemary Expansion

In Nakuru, Joyce started her herb venture on a tiny scale. She purchased 100 high-quality, certified rosemary seedlings from a local nursery to act as her “mother garden.” She planted them in highly fertile soil near her house and cared for them for 8 months until they grew into large, bushy shrubs.

Instead of spending Ksh 30,000 to buy 3,000 new seedlings to expand her farm to a quarter-acre, Joyce took 3,000 cuttings from her 100 mother plants. She rooted them in simple propagation beds filled with river sand under a basic shade frame. Within 6 weeks, over $90\%$ of her cuttings had developed strong root systems. She transplanted them into her newly prepared quarter-acre, expanding her farm size virtually for free.

Propagation Methods by Herb

Herb	Primary Propagation Method	Best Source Material	Rooting Time	Field Transplant Ready	Success Rate Tips
Rosemary	Stem Cutting	Semi-hardwood stems ( $10\text{-}15\text{cm}$ )	3–4 Weeks	6–8 Weeks	Use sharp blades; clean cuts prevent rotting
Thyme	Stem Cutting	Softwood/semi-hardwood stems	2–3 Weeks	5–6 Weeks	Keep medium moist but never waterlogged
Mint	Rooted Runners	Horizontal surface vines with roots	Direct Rooting	Immediate	Plant directly into wet beds; water daily
Lemongrass	Slips (Clump Division)	Individual rooted stalks	Direct Rooting	Immediate	Cut top leaves to $15\text{cm}$ to reduce water loss
Sweet Basil	Seed (Propagated in Trays)	High-quality certified seed	5–7 Days (Germination)	4–5 Weeks	Avoid propagating basil from cuttings commercially

Crucial Things to Keep in Mind:

Sterilize Your Tools: Always clean your cutting blades with a mixture of water and methylated spirit before starting. Dirty blades spread fungal diseases from plant to plant.

Sand is Key for Cuttings: Never try to root stem cuttings in ordinary garden soil; it is too compact and lacks the air spaces required for new roots to form. Use clean river sand.

Keep Cuttings Cool: Keep your unrooted cuttings under $50\%$ shade netting. Without roots, they cannot drink water, so they must be shielded from the hot sun to prevent drying out.