Plant Propagation: Seed, Cuttings, and Division

Plant Propagation: Seed, Cuttings, and Division

Propagation is how growers multiply plants reliably and economically. In this practice lesson you will use three fundamental methods—direct seeding, stem-tip cuttings, and crown division—and document every result in a propagation log. Accurate records are not optional; commercial greenhouse production depends on knowing what worked, when, and why.

Sanitation: The Foundation of Every Propagation Method

Disease organisms spread faster in propagation areas than anywhere else in the greenhouse because the environment—warm, humid, low-light—favors pathogens and the plant material has no protective bark or cuticle. Before touching any plant material, sanitize all cutting blades and bench surfaces with 70% isopropyl alcohol. Let the blade air-dry before use; alcohol residue can damage tissue. Replace solution when it becomes cloudy. Never use the same unwashed blade on a second stock plant without re-sanitizing. Wear nitrile gloves when handling rooting hormone to avoid skin exposure.

Seed Propagation

Seeds are the most economical starting point for many annuals and vegetables. The key variables are medium, moisture, temperature, and depth.

Propagation mix is a soilless blend—typically peat or coir, perlite, and vermiculite—that drains freely while holding enough moisture for germination. Never use field soil; it compacts and carries pathogens.

Filling 72-cell plug trays: Overfill the tray, then strike off the excess with a straight edge. Firm gently—cells should be full but not compacted. Pre-moisten the medium until it holds its shape when squeezed but releases only a drop or two of water.

Sowing: Read the seed packet. Depth is usually one to two times the seed diameter. Fine seeds (petunia, begonia) are sown on the surface and not covered. Place one or two seeds per cell depending on germination rate expectations. Label every tray immediately with crop name, variety, and sow date—memory is not a propagation tool.

Germination environment: Most warm-season annuals germinate best at 70–75 °F substrate temperature. A germination chamber or misted bench maintains humidity. Check daily. Remove trays from the germination chamber promptly once 50–60% of seeds have emerged to prevent stretching.

Recording results: Count emerged seedlings at Day 7 and Day 14. Germination percentage = (number of emerged seedlings ÷ number of seeds sown) × 100. Record both counts in your propagation log.

Stem-Tip Cutting Propagation

Stem-tip (terminal) cuttings reproduce a plant genetically identical to the parent—critical when maintaining a specific flower color or growth habit.

Selecting cuttings: Choose healthy, pest-free stock plants. A good cutting is 3–4 inches long, has at least two nodes, and is neither too soft (wilts easily) nor too woody (roots slowly). Take cuttings in the morning when plants are fully turgid.

Making the cut: Use a clean, sharp blade. Cut just below a node at a 45-degree angle to maximize the rooting surface and improve drainage away from the cut end. Remove leaves from the bottom one-third of the cutting to prevent rot where the stem enters the medium.

Rooting hormone: IBA (indole-3-butyric acid) is the industry standard active ingredient. Powder and gel formulations are both widely used. Dip the basal cut end into powder (tap off excess) or apply gel with a clean applicator. Do not double-dip the container—pour a small amount into a separate dish to prevent contaminating the stock supply. Rooting hormone concentration varies by species; follow label directions.

Sticking and environment: Insert cuttings into pre-moistened propagation medium in 50-cell trays at a depth that keeps them upright—typically 1–1.5 inches. Tent with clear poly film to maintain humidity above 85%. Avoid direct sun under the tent; diffuse light prevents overheating. Mist the interior if condensation disappears. Evaluate rooting at 14–21 days by gently tugging a cutting; resistance indicates root formation.

Crown Division

Crown division is the simplest vegetative method for clump-forming herbaceous perennials such as hostas and daylilies. It requires no rooting hormone and no special environment, but each division must be viable.

What makes a division viable? Each piece must have an intact root system and at least one growth point (bud, eye, or shoot). A division with roots but no growth point will not grow. A shoot with no roots will die.

Technique: Lift or remove the plant from its container. Use a clean, sharp spade, knife, or hand pruners to cut through the crown. Minimize tearing. Aim for four or more divisions of roughly equal size. Trim any dead or damaged roots. Pot immediately into 4-inch pots with moist growing medium. Water in gently. Label each pot with species name and division date.

Assessment: New shoot emergence within two weeks indicates a successful, viable division. Record emergence date and status in your propagation log.

Completing Your Propagation Log

Your log must include: date of activity, species and variety, propagation method, number of units started, count and percentage at each evaluation date, and any observations (disease, environmental deviation, technique notes). A complete log is your evidence of competency and your reference for future crops.