You will need to grow two batches of plants; the rootstock and the fruiting cultivar (variety). All the well-known cultivars (varieties) will graft.
- Sow tomato rootstocks seed a few days earlier than the fruiting cultivar as the seed is somewhat slower to germinate. The germinating temperature should be 17–21°C (65–70°F).
- High light levels are vital – seedlings can very quickly become leggy – greenhouses are ideal, but windowsills are more challenging.
- When the seedlings have reached the expanded leaf stage, they are ready for pricking out into individual 7.5cm (3in) pots.
- They should be grown on in a lower temperature of 13–16°C (56–60°F).
Plants are ready for grafting when they are at least 10cm (4in) tall and have a good stem thickness.
Wash hands thoroughly before working on the plants. Choose rootstock and scion plants with similar size and thickness of stem for grafting.
What you will need: A very sharp sterilised blade, such as a scalpel or razor blade (to minimise bruising of the stems), grafting clips* (or Sellotape), clear plastic bag or covered propagator. *Grafting clips are readily available from online suppliers.
Wedge (or cleft) grafting step-by-step (suitable for tomatoes and many other grafted vegetables)
- Rootstock preparation: Cut off the upper stem of the rootstock and discard, retaining the base. Make a vertical slit up to 1cm (½in) long into the top of the cut-off stem.
- Scion preparation: Cut off the upper stem of the scion but retain the upper part and discard the base. Cut the base of the scion into a V-shape.
- Insert the scion base into the slit of the rootstock to complete the wedge graft.
- Secure the two halves of the wedge graft with a grafting clip. Sellotape could be used instead of a grafting clip to wrap around the union but can be very fiddly.
- Cover immediately with a clear plastic bag or covered propagator. Place out of direct sunlight and keep at 15-19°C (59°F-63°F).
- Uncover daily to air plants and check watering. Keep moist but not wet. Note: adventitious roots may form up the stem if conditions are too humid.
- Once the graft union has calloused and plants are growing strongly (around two to three weeks), remove all covers and clips or Sellotape.
Other grafting techniques
Variations on the wedge grafting technique can also be very successful. These include the saddle graft (inverted V) and the splice graft. See photo gallery for details.
The approach (side-by-side) graft may also be used but takes up more space since the top and bottom of both the rootstock and scion are retained until the graft union has taken.