What You’ll Need to Graft Tomatoes (including a bit of crazy)

by Marty Fisher, EMGV

It’s mid-March. A cold, raw, wet Sunday. But inside my greenhouse, it’s a humid 70 degrees. What a joy to fiddle with my plants wearing a tank top, listening to NPR!

IMG_0734The tomatoes I planted on February 17 are thriving. I’ve decided it’s almost time to graft—not a decision I take lightly. I will have to chop the heads off of my precious baby heirlooms—12 six-packs of seedlings (72 plants). These will be the “scions”—the fruit-bearing part of the plant. I will also chop the heads off of 12 six-packs of Maxifort seedlings. They are the strong rootstock that will play host to the vulnerable heirloom scions through the growing season.

But first, in case you want to jump into this boat with me and spend FAR too much time and money on heirloom tomatoes that you could just buy at Whole Foods or the Farmer’s Market (I promise you, these homegrowns will far out-taste anything you can buy anywhere …) here is the equipment you will need for grafting. I’ve provided a list of resources so you can explore and adapt for your own situation and tastes.

#1 A sunny spot in a warm environment

A greenhouse is wonderful, but not at all essential. A south-facing window of your home will do just fine. The temperature should stay between 60 and 75 degrees. Be sure to rotate your trays so plants don’t bend to the light.

#2 Rootstock seeds

I chose Maxifort. It has high vigor, is suited to a long growing season and large fruited scions, and has resistance to the viruses our tomatoes seem susceptible to. There are a number of different rootstocks with different disease resistance and growth profiles. These are described in the accompanying resource, How to Graft Tomatoes, by Nathan and Telma Reed.

#3 Heirloom seeds

Picking out heirlooms is the fun part—I like to spend January leafing through seed catalogues, reading descriptions, and narrowing the list. Our selections this year include some new varieties, but most are tried and true:

Amana Orange – a glowing orange beefsteak

Azoychka – from some no-doubt nice Russians, yellow with a citrusy flavor

Carbon – black/red with award-winning smoky flavor

Paul Robeson – black/red, named for one of the first black opera singers, which is why I chose it—deep and delicious

True Black Brandywine – big black/red old-fashioned favorite

Ananas Noire – stunning, big green, red, and black pineapple-type

Pineapple – large red and yellow

Green Zebra – small, tangy green with lighter stripes

Lucky Tiger – green and red-striped oval cherry tomato

Lemon Boy – sweet lemon yellow, smaller fruited, prolific producer

Thornburg’s Terracotta – delicious. Strangely, it is actually the color of a clay pot

Brad’s atomic grape – multi-colored, blue, black, yellow—this one is new to me, and not an heirloom, but not disease-resistant either

#4 Normal seed starting supplies

Commercial seed-starting mix

Plant labels and marker (I use wooden ice-pop sticks)

6-pack growing containers (I use recycled containers from garden centers)

Insert tray with holes for drainage (tray holds 6 6-packs, for 36 plants)

Tray that holds water (insert tray should fit inside—this accommodates bottom watering)

Clear 7-inch humidity dome with vents

3-inch pots for transplanting root stock prior to grafting

Potting soil

Heat mat (This is nice to have, but not essential if you have a warm environment)

Spray bottle for water (for misting inside the dome—never directly spray the plants)

#5 Special supplies for grafting

Grafting clips for joining scion to rootstock (I use plastic spring-loaded clips, but many suppliers recommend silicon clips)

Disposable scalpels (double-edge razor blades also work well, but the scalpels have a handy handle)

Shade cloth—pieces of light-filtering cloth in gradations of 90%, 60%, 30%, 10%. Newly grafted plants are first placed in total darkness, and then the cloths are adjusted to gradually reintroduce them to light.

A Multi-Dimensional Summer Experience

I know, all of this sounds complicated. To me it is a combination of fascination, anxiety, frustration, and gratification. To walk into a grocery store, pick up a carton of “heirlooms,” and take them home and eat them would just be too easy, and too, well, one-dimensional. When our family gathers around a plate of heirloom tomatoes, tastes them, debates each one’s merits, and discusses the ins and outs of growing them, well, it’s just a robust, multi-dimensional summer experience.

Stay tuned for play-by-play grafting!

Yum! Why would you want just plain red tomatoes when you could enjoy these beauties?
Each flat consists of a non-draining bottom tray, a draining insert, 6-packs for seedlings, and a vented humidity dome.
Root stock seedlings of Maxifort have been transplanted from their initial 6-packs to individual 3-inch pots. This will provide space for the grafted plants to grow until they can be transplanted into the garden.
Heirloom seedlings will be the “scions.” They will be cut and grafted onto the Maxifort root stocks. It is something of a balancing act to have both sets of seedlings close to the same stem size on grafting day.
Timing is critical to avoid “flopping.” This is when the stems of the seedlings become contorted—either from bending to the light, getting too tall, or getting too dry. It is almost impossible to graft seedlings when the stems are not straight and of similar circumference. Before grafting, I like to use spring-loaded grafting clips with bamboo skewers to help keep stems straight.

Grafting Supplies are available from a wide variety of garden suppliers. Here’s a list of what you may need and suggested online search terms.

Heat mat (not essential) — Search on “heat mat for seedlings.”

Non-draining trays and Humidity Domes — Search on “seed propagation trays” and “humidity dome for 1020 tray.” I use 1020 trays, extra strength, no holes and seven-inch humidity domes. Both come in packs of 5 or 10 trays.

Scalpels — Search on “disposable scalpels” and choose #11 high-carbon steel blades, 10 per box.

Grafting clips — My favorite spring-loaded grafting clips are clear with two openings to accommodate stems from 1.5mm (1/16-inch) to 4mm (5/32-inch) in diameter. They are available from Johnny’s Seeds and David’s Garden Seeds.

Shade cloth — Many places sell shade cloth in various light filtering percentages, but the only place I found that would cut the cloth to a custom size was Greenhouse Megastore. I recommend light filtering percentages from 10% to 90%.

Rootstock Seeds — Johnny’s Seeds, Harris Seeds, and Territorial Seeds all carry a variety of rootstock seeds with descriptions of their disease resistance and growth profiles.

Heirloom Seeds — Available from a variety of garden suppliers.

Reed, N. and T. How to graft tomato plants–a guide for the backyard gardener.