© Andrew Mefferd. All rights reserved.
Grower cuts tomato scion plant at a 45 degree angle underneath the cotyledons until the entire top of the plant is severed.

Boost Yields & Prevent Disease with Grafted Tomatoes

Orchardists, breeders, and fruit enthusiasts have utilized the benefits of grafting fruit trees for thousands of years. More recently, the technique has taken hold of the market garden and backyard gardening world for annual vegetables like tomatoes, eggplants, and cucumbers. Grafting is especially beneficial for growers in hot, humid regions with mono-cropped soil decimated by disease. 

On the surface, the method requires additional costs and knowledge, and rootstock seeds are relatively pricey, so many growers shy away from grafting. However, decreased disease pressure, increased yields and vigor, and an extended season may make you reconsider. 

You can confidently graft your tomatoes with our guide to grafting, along with ample research, adequate tools, and a proper grafting station. Whether it’s your first year or you’re attempting a new method, we’ve got you. Keep reading to learn how to graft tomatoes, along with pro tips to ensure your tomato season is healthy and abundant.

© Andrew Mefferd. All rights reserved.
Grafted tomato plants healing in greenhouse.

What is Tomato Grafting?

Grafting is the strategic combination of a hybrid rootstock and the tomatoes you love to grow, eat, and sell. Tomato rootstocks are bred to grow vigorously to resist common tomato diseases but not to produce fruits. Rootstocks tolerate abiotic stressors like colder soil and inclement weather conditions better than non-rootstock varieties. 

The desirable tomatoes are called the scions in the grafting scenario. You’re after the rootstock's good traits, like a robust root system, disease resistance, tolerability of poor soil conditions, and the scion's fruit. You’ll sow rootstock and scion seeds within a few days of each other, and on the grafting day, you’ll behead them all, match them up by stem girth, and hold them together while they heal. The rootstock is in control in the soil, and the scion is in control vegetatively. 

Many gardeners love growing heirloom tomatoes like ‘Green Zebra’ and ‘Cherokee Purple,’ known for their distinct old-timey flavors, gorgeous colors, and funky shapes and sizes, but not always for their high production and health. Grafting allows heirloom enthusiasts to grow their favorite heritage varieties and save seeds while observing increased vigor, disease resistance, and yields. You may end up with so many tomatoes after grafting that you’ll need to start selling them! Learn how in How to Start Selling Market Garden Produce. 

Tomato seedlings growing in soil blocks.

Soil Blocks vs. Container-Grown Tomatoes: Which is Best for Grafting?

Soil blocks may produce healthier seedlings than cell trays that don’t offer excellent drainage or allow air to reach the plant from the bottom. However, a study at Michigan State University found no significant yield increases in soil-blocked tomatoes over container-grown ones. Decide through trial and error if the extra work is worth it in your garden setup. Check out Soil Blocking 101 to learn how to start soil blocking this season with our soil-blocking starter kit. Reap all the benefits of soil blocking without knowing the skill with our air-pruning 72-cell air prune trays for seed-starting and 2.5,” 3.3,” and 5” heavy-duty pots for up-potting. 

Provide ample space as plants grow in containers, up-pot as needed, and don’t allow them to become stressed or rootbound in their pots. Air-pruning containers encourage roots to venture out through the air vents, which will cause them to die off. This sends a message to the mother plant to produce more feeder roots, leading to an advanced, robust root system and a healthy transplant. Read How to Transplant and Up-Pot Seedings to learn more. 

Related: Urban growers should check out Growing Tomatoes for the Urban Farm for growing motivation from Dallas 1/2 Acre’s Michael Bell.

Essential Tools & Materials for Successful Tomato Grafting

Although the tools required for grafting are basic and inexpensive, securing high-quality, clean, and sharp ones will positively impact your results. 

Must-Have Supplies for Beginners

• Miter-cut grafting knife or clean, sharp razor blade

• Sterile cutting tools for snipping leaves

• Grafting clips (silicone tubing) ranging from 1.5 to 3 mm or grafting tape 

• Labeling materials like our color-coded plant labels

• Rootstock and scion plants or seeds to sow your own

• 1020 humidity dome or plastic bag

• Water mister like the Kwazar mercury trigger sprayer

Healthy seedlings will transition to the healthiest grafted seedlings, so start with fresh, viable seeds, new soil or sterile soilless media, and a clean workspace. Read The Ultimate Indoor Tomato Seed Starting Guide for Gardeners and How to Use a Humidity Dome for Seed Starting to learn more about starting seeds at home. 

Tomatoes are tropical fruits, so they’ll germinate best at 70° to 80°F (21° to 27°C). We recommend using a heat mat to ensure consistently warm temperatures for high germination rates. Read How to Use Heat Mats for Starting Seeds for more info. 

Optional Tools for a Higher Success Rate

• Disinfectant for tools

• Healing chamber 

• Support stakes 

• Replacement razor blades

• Small seed-starting pots for the rootstocks

• Stainless steel strip harvesting knives if performing top-wedge or side tongue graft

• Heat mat if starting seeds at home

A healing chamber can be as small as a single 1020 tray with a humidity dome or a rubber storage tote for backyard growers and homesteaders or as large as a DIY healing chamber made from insulation boards for larger-scale growers. It can also double as a germination chamber for seeds that require total darkness to sprout. 

This propagation kit was specially designed for cuttings and graftings as the clear pots allow you to monitor root development without disturbing delicate plants. 

Pro tip: Start your rootstock seeds in small pots and your scion seeds in a cell or strip tray. This method will ensure no confusion when it comes to grafting, and all the grafted seedlings end up in small pots that are easily moved around and organized by the cultivar. 

© Andrew Mefferd. All rights reserved.
Scion seedlings in a 72 cell air prune tray.

Select Your Tomato Grafting Method

There are three main tomato grafting methods to choose from based on your goals and experience-level. In this article, we'll focus on the top-graft or splice method because it's the most common grafting method for tomatoes, scalable, and very beginner-friendly.

Splice or Top-Graft

This is the most commonly used method for tomato grafting. 

How to do a Splice or Top-Graft

An identical diagonal cut is made on rootstocks and scions.

The scion tops are matched up to rootstock bottoms, and a silicone clip that matches the girth of the stems holds them together as they heal.

The plant naturally outgrows the clip as it expands in stem diameter. 

Top-Wedge or Cleft Graft

This method has a relatively high success rate! For more information, the Horticulture Innovation Lab at UC Davis details this method in their Tomato Grafting Guide.

How to do a Top-Wedge or Cleft Graft

A wedge shape similar to a flathead screwdriver is cut into the scion stem. Next, make a ½ inch cut into the center of the rootstock stem. 

Wiggle the blade back and forth a few times while it’s in the incision to help loosen it up. Then, wedge the scion into the rootstock and wrap the graft with plastic or graft tape.

Side Tongue Graft

The side tongue grafting method is best when used on larger tomato plants, but more commonly used on cucurbits and fruit trees. It's a bit trickier than the others, but it maximizes the cambium, or cellular plant tissue surface area in contact, speeding up the healing process. 

How to do a Side Tongue Graft

Make a slanted cut on the scion and rootstock as similar as possible. Then, make a “tongue” cut down the center of the stem. They should wedge together. Wrap the graft with tape or use a clip to secure them together. 

Preparing for Grafting

When sowing seeds at home, start the rootstock seeds a few days after the regular tomato seeds. Since they grow more quickly and vigorously, this will ensure they are more compatibly sized when it’s time to graft. 

A few of the best rootstock options include ‘Maxifort,’ ‘Fortamino F1,’ ‘Estamino,’ and ‘DRO141TX.’ 

It's Grafting Day!

Create a clean and clear workspace and gather all your supplies. Ensure tools, blades, and pots are sanitized and clear of debris. 

Observe the rootstock and scion plants and ensure enough of them align in size. Ideally, the stems are close to the same diameter, and the plants are healthy. 

If your scions are too small, allow them to grow for a few more days to ensure the grafts “take.” Additionally, the scions shouldn’t be much larger than the rootstock, or the seeding may topple over from the weight. If your scions are more prominent, a quick hack to avoid them toppling is to snip off most leaves to remove unnecessary weight. 

© Andrew Mefferd. All rights reserved.
Split image of rootstock growing in 2.5" pot with razor angled 45 degrees underneath cotyledons and rootstock with entire top cut off.

Step-by-Step Guide to Tomato Grafting

Making the Graft Cuts

STEP 1

Identify and mark the cutting points on the rootstock and scion. You want the grafted seedlings to be about the same height as before the cut to avoid top-heaviness. Remove cotyledons, suckers, and lower leaves that are in the way. Cut the rootstock below the cotyledons to prevent suckers from forming. 

STEP 2

Make a clean diagonal cut at a 45 degree angle on the rootstock stem with your grafting knife or blade and remove the top. If using a spring-loaded miter-cut grafting knife, note your hand placement on the handle and repeat it for each cut to ensure the angle matches up. 

Pro tip: Have a specific container or box for discarded rootstock tops to avoid confusion. You don’t want to accidentally graft a rootstock's top onto a rootstock's bottom.  

STEP 3

Cut the scion below a healthy set of leaves. Remove any that are in the way of your grafting area. Depending on how many plants you’re grafting, you may cut all of one variety at a time, graft them, and then move on to the next. While you may feel pressure to work quickly after cutting the heads off seedings, they won’t perish immediately. Take time, work confidently, and ensure the grafts are properly done. 

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Grafting clip being placed over the graft union to hold connection in place.

Connecting the Rootstock and Scion

STEP 4

Align the cut surfaces of the rootstock and scion to ensure most of the cut surface areas are touching. If the cuts don’t line up, carefully make a second cut. 

Pro tip: Sow extra scion seeds to create wiggle room when working. You may need to toss out some scions, and that’s okay!

STEP 5

Position a grafting clip, plastic wrap, or tubing so the graft union is in the center. Hold it up to ensure there isn’t space between the cuts, or it will not heal. Make adjustments as needed. 

Pro tip: If the stem is between clip sizes, opt for the smaller one to ensure it doesn’t slip out. 

© Andrew Mefferd. All rights reserved.
Grafted tomatoes healing under cover of humidity dome in a greenhouse.

Providing Optimal Healing Conditions

STEP 6

Place the grafted plant in a controlled humidity environment. This could be a humidity dome, a plastic bag, or a healing chamber. The humidity level should be between 85 and 95%. Note that too much humidity and condensation can lead to failure of the grafts and death. Monitor levels with a basic digital indicator device.  

In a chamber, directly mist the plants or the ceiling to create humidity. Inside a humidity dome, spray the top of the dome. Keep the door or lid closed except once daily to mist. Ensure 100% darkness for the first few days. It’s important to note that the scion cannot uptake water from the rootstock for the first week after grafting, so humidity is the plant’s only water source.

STEP 7

Gradually acclimate plants to normal conditions over 7-10 days by introducing indirect light for a half day, then a full day, then transitioning to direct light from the sun or artificial grow lights. If there are signs of stress at any point, transition them back to the prior step. Think of this as a more advanced version of hardening off plants. 

Common Tomato Grafting Problems and How to Solve Them

Watch for these common tomato grafting problems so you can avoid them. 

Poor Graft Alignment

Finding compatible rootstocks and scions to graft your first time can be tricky. Do your best to find two that are the most alike in diameter for best results. Gently tug on the first few after you clip the graft to ensure proper alignment and security, then leave them to heal. 

Wilting

Wilting may occur if plants' healing environment is too cold or drafty, not humid enough, or they are introduced to light too early. Watch for signs of stress when introducing new conditions, such as a bit of light or decreased water, and adapt as needed. Pro tip: Ensure consistency of humidity between 85% and 95% and a temperature of around 75° to 80°F (24° to 26°C) by adding a temperature and humidity monitor inside your healing chamber. Adjust as needed. 

Failure to Heal 

Beginners often overcomplicate the grafting process on the first try, which may lead to plants’ failure to heal and thrive. Have confidence in the process, don’t bother them too much, and avoid overwatering. Plants need time to heal after being cut and spliced, so give them undisturbed time.

Disease Issues

If you sow seeds at home, start with seeds and soil from reputable sources. Otherwise, purchase your plants from a trusted source. Always use clean tools and a disinfected workspace. Monitor humidity levels and wet foliage to reduce the risk of foliar diseases. 

Graft Line Buried

When transplanting grafted tomatoes, you must keep the graft line one to two inches above the soil line to ensure its success. The adventitious nature of tomatoes will cause them to set roots from any stem location that comes in contact with soil. This will allow the scion to set roots, which negates the graft altogether. Check the graft line location if a tomato plant is smaller, and less productive than others, or is diseased. If the scion roots above the graft union, cut them off to avoid them getting into the soil. Once roots are set, there is no coming back from the results. 

© Andrew Mefferd. All rights reserved.
Grafted tomato plants healed and planted in soil. You can see the scar on the stem where the graft union is.

5 Major Tomato Grafting Benefits

If you're not yet sold on grafting tomatoes this season, here are five excellent reasons to try it.

1. Increased Disease Resistance

   When you start grafting tomatoes, the risk of common diseases like Fusarium wilt, tomato mosaic virus, blight, and root rot, to name a few, will reduce. This is important for small-space growers or those with only one high tunnel or hoop house where tomatoes are grown. Diseases can stay in the soil for up to ten years, but grafted tomatoes can resist them, allowing us to grow in the space longer without giving the soil a "break."

   Grafting also decreases the need for growers to use pesticides, lowering costs, labor, energy, and resistance. Note that grafted tomatoes will require a more advanced trellis system. Our article Building Trellis for Indeterminate Tomatoes includes our recommendations for trellising systems in hoop houses.

2. Higher Yields

   Rootstock's vigor translates to increased foliage, trusses, flower, and fruit production. It's not uncommon to see a triple truss on a grafted tomato plant loaded with cherry tomatoes. Pruning their vigorous vegetative growth will be vital for their continued, long-term success. Remember, tomato plants can tolerate ⅓ of their foliage's removal without adverse effects. Pruning Indeterminate Tomatoes for Maximum Production in a Hoop House discusses how to get the most out of your high-tunnel tomatoes by properly pruning them.

   Tomatoes out of control? We've got an article for that, too. Managing Overgrown Tomatoes

3. Improved Drought & Stress Tolerance

   Rootstocks can tolerate wet, cool soils, extreme temperature fluctuations, drought stress, soilborne diseases, and stressors like acidic or alkaline soil and soil nematodes. Each rootstock cultivar offers slightly different perks. For instance, 'Maxifort' is known for its long-season capabilities, whereas 'CRA66' is most successful with open-pollinated varieties. Ensure the rootstock you select aligns with your needs.

4. Extended Growing Season

   Rootstocks tolerate colder soil temperatures and inclement weather while resisting many common tomato diseases. Transplant grafted seedlings earlier in the season and harvest later than usual, adding weeks or months to your season. Note the transplant, prune, first harvest dates, and total harvest weights of a non-grafted vs a grafted 'Cherokee Purple' tomato plant for a true comparison and proof of season extension.

5. Better Flavor & Fruit Quality

   Grafted tomato plants produce more marketable fruits with decreased shape irregularities and blemishes. Additionally, healthy plants have the energy to continue producing attractive, uniform fruits for longer.

   While some taste-testers don't notice a flavor difference in grafted tomatoes, there are promising studies such as this one from China, Rootstock-scion interactions affect fruit flavor in grafted tomatoes that showed they had increased sweetness levels when heterografted. Heterografted tomatoes are grafted onto a different plant species, such as an eggplant.

Still can’t decide whether tomato grafting is right for your setup? Check out Penn State Extension's To Graft or Not to Graft. 

© Andrew Mefferd.All rights reserved. Top cut off of a rootstock tomato plant at 45 degrees.

FAQs About Tomato Grafting

What is the best time of year to graft?

Sow your scion seeds about four weeks earlier than you would typically sow non-grafted tomatoes to account for the grafting and healing time. Consider your growing area, healing space, and forecasted weather to ensure you can plant them out when they’re ready. If not, plan to up-pot to ensure they have the space and nutrients required. 

How long does it take for grafted plants to heal?

Under the right conditions, grafts can heal in five to eight days, and the wound should heal in two weeks. Allow the clips to work themselves off as the stem diameter increases. At this point, you can gather them from the soil surface, sanitize them, and store them for next year. 

Do I need special training to graft tomatoes?

While you don’t need special training before grafting tomatoes, we recommend watching videos, joining webinars, and researching the process before diving in. Set up grafting and healing areas for best results. You’ll improve each time you perform the task and learn the signs of failure and success. 

Can I graft different tomato varieties together?

Yes, you can graft different tomato varieties together to increase your diversity within a small area. You’ll see the best results if new grafts are spliced onto a mature plant in the ground. This method requires you to wrap the new graft securely and cover it with a plastic bag.

How do I prevent grafted plants from wilting?

Grafted plants will almost always wilt during the first few days after you perform the graft. You did just cut them in half, after all. Provide them with a safe environment to heal, and they should perk up within a week. 

What is the success rate for tomato grafting?

Beginner success rates are typically around 60%, which can quickly increase to closer to 90% to 100% with experience. Timing, size, tools, confidence, healing chamber, seed health, and technique will all impact your results. Cornell’s collection of pro tips from years of trial and error might also help. 

If you're interested in learning more about tomato grafting and other advanced techniques for organic vegetable production, check out The Greenhouse and Hoophouse Grower's Handbook by Andrew Mefferd.