This guide walks through the process of tomato cleft grafting, including best practices and illustrative photographs.
Grafting tomatoes can raise income potential, but must be executed correctly to be effective. The steps are broken down into five stages: preparation, sanitation, grafting, healing and acclimation, and planting.
A Quick Guide to the Cleft Graft Method
- Rootstock and scion varieties must be genetically compatible. Therefore, select varieties proven to be compatible through experience or research.
- Note that all the seed that are sown will not result in a grafted plant suitable for field use. Seedlings and grafted plants are lost in at least four ways:
- Lack of emergence,
- Seedling quality and survival (some seedlings may perish before grafting or be unsuitable for the process),
- Graft survival (some grafts will be unsuccessful), and
- Graft quality or survival (some grafts are successful but the grafted plant is not suitable for field use). Therefore, when sowing seed, anticipate these losses. Then, sow more seed or purchase more plants than is required for fruit production.
- The following facts also influence when and how many seed should be sown:
- Seedlings grow at different rates depending on variety,
- Rootstock stem diameter must reach a minimum size to graft, and
- Rootstock and scion seedling stem diameters must be similar.
- Therefore, early and repeated sowings are recommended.
- Grafting only vigorous, disease-free seedlings is highly recommended. These seedlings may be easiest to produce in a low or high tunnel.
- When preparing to graft, assemble the following:
- Scion and rootstock plants (some grafters presort plants according to size to save time),
- New razor blades or scalpel,
- Clips, glue, ties, or strips to secure the graft,
- Sanitation supplies (e.g. alcohol, detergent, bleach or a commercial disinfectant for hands, surfaces and plants, oil burner, gloves, bench paper), and
- Clean, climate controlled spaces to a) assemble grafts and b) heal and acclimate grafted plants. A low or high tunnel may be ideal for healing and acclimation.
- Minimize the onset of seed-borne disease; use clean, high quality, treated seed and avoid tobacco use. Seed suppliers and farmers can treat seed using recommended methods involving, for example, hot water and/or chlorine.
- Minimize disease transmission during growth; keep seedlings in a properly sanitized space and always wash hands before and after touching seedlings to prevent the mechanical spread of pathogens.
- Minimize disease transmission while grafting; always keep work spaces clean with detergents and alcohols, wear gloves while grafting, and use new or cleaned implements.
- Select healthy rootstock and scion seedlings of a similar stem diameter.
- Using a sharp, clean blade, decapitate the rootstock seedling with a horizontal cut approximately 5 mm below cotyledons.
- Bisect the truncated rootstock stem at its widest diameter to a depth of 4 mm.
- De-root scion seedlings with a horizontal cut approximately 5 mm above the cotyledons.
- Trim the cut surface of the scion seedling to the shape of a wedge containing sides approximately 4 mm long. (In the two cut process, two diagonal cuts at a 65 degree angle are made that simultaneously separate the scion from its roots and forms the wedge).
- Insert the trimmed scion into the vertical slit of the rootstock.
- Secure the graft – a clip, tie, polyethylene strip, wire, glue or other clean material may be used.
Healing and Acclimation
- Place new grafts in a climate controlled chamber with humidity at 90% (maintained by plastic), light reduced by 50% (maintained by shade cloth), and a temperature range of 18-21 deg C (day) and 16-18 deg C (night) for 5-7 days. Bottom watering is suggested in order to reduce stress on the graft union and limit the chance of decay.
- Place week-old grafts in a second post-graft chamber with humidity at 50% (maintained by plastic), light increased by the removal of the shade cloth, and a temperature range of 18-21 deg C (day) and 16-18 deg C (night) for 5-7 days. Bottom watering is still important to reduce stress on the graft union.
- Place two-week old grafts in an area with humidity, light, and temperature ranges recommended for acclimating tomato seedlings prior to planting.
- Plant the grafted plant so that the graft union remains at least 2.5 cm above the soil line. A rule of thumb is “don’t bury the clip,” if it remains. Proper placement of the plant limits root formation from the scion.
- Grafts may develop shoots from the rootstock and/or roots from the scion. Observe plants after planting; prune if needed.
More detail available in the full PDF version: Tomato Grafting Guide (PDF).
This guide was created for a September 2011 workshop with additional distribution.