Grafting Heirloom Tomatoes

Thursday, April 25, 2013

I love growing heirloom tomatoes.  An heirloom tomato is a variety that has been passed down from generation to generation because of its desirable qualities such as appearance and taste.  My favorite is Marianna’s Peace, a large pink beefsteak with a wonderful old time tomato flavor.  Unfortunately, my garden has a soil borne disease that makes it impossible to grow these luscious tomatoes.  While I do grow a few in pots, I have found a way to circumvent my soil problems. Modern hybrid tomatoes have been bred to resist all sorts of diseases. Wouldn’t it be great to have both the taste of an heirloom and the disease resistance of a hybrid? Well, there is a way. It’s called grafting.  Grafting is the process of taking the top of one plant (scion) and uniting it with the bottom of another (rootstock).  Grafting an heirloom tomato top onto a disease resistant hybrid tomato rootstock not only improves soil borne disease resistance, but can improve plant vigor and yields because of increased nutrient uptake by the stronger root system.

The grafting process is easy.  All it takes are two tomato seedlings (one heirloom and one hybrid) and two 45° cuts. It’s the preparation that takes planning.  First, determine the variety that you want to grow for fruit (the scion).  Then pick a rootstock to graft onto. Any disease resistant variety will do.  I use a variety called Maxifort, which is a disease resistant rootstock specifically for grafting (  It is expensive, but I find it very robust in my Fusarium infested soil.

Here’s what you’ll need:

Disease resistant tomato seeds for rootstock
Tomato seeds for the scion (the tomato you want to grow)
Seed starting mix
2” Seed starting pots1.5 mm grafting clips (available from Johnny’s Select Seeds)

Grafting guide (to help you make a precise cut)
Brand new razor blade, disinfected with alcohol
12” tall humidity dome (large, clear plastic food container)
Spray bottle with room temperature water

Starting seeds.  I prefer to start both varieties in separate 2" pots.  I start the scion (heirloom) seeds four days before I seed the rootstock. I find that Maxifort sprouts quickly and grows fas

ter than the heirloom tomato seedlings. I make sure that the pot has soil level to the top of the rim.  That way the tomato plant growth will be higher than the rim which makes the stem easily accessible for cutting.   After the tomatoes have sprouted, I check the growth until both the scion and rootstock stems have reached 1.5 mm in diameter to match the grafting clips that I use. 
Make a grafting guide.  A grafting guide is simply a raised flat surface to lay the tomato stem across while making the cut.  I use a 2” thick piece of wood with a 45° line drawn across.

Once the scion and rootstock have reached the correct diameter, it is time to graft.  On the big day you will need a sterilized razor blade, grafting clips, grafting guide, a humidity dome (I use a large clear square plastic food container), a spray bottle and a steady hand. 

Remove the lower leaves on both seedlings. Mark the rootstock and scion where you want to cut.  Lay the rootstock tomato plant pot on its side on a flat surface with the stem on the grafting guide.  Line up the razor blade with the 45° line on the guide.  Make a firm cut across the stem.  Slide the grafting clip halfway onto the cut rootstock stem.  Cut the scion on the same 45 ° angle at the 1.5 mm mark.  Slide the scion in the grafting clip, aligning the cuts as best as possible.  Heavily mist the new plant. This is important because it is the only moisture the scion will receive until the graft heals.  Cover with a humidity dome and keep out of direct sunlight (mine stay under fluorescent lights).  Mist the new plant at least twice daily for nine days.  Expect the plant to wilt slightly the first few days.  After nine days you should have a healed graft. Remove your new plant from the humidity dome when the graft is well healed. Transplant the tomato plant into the garden with the graft above the soil line.  Sit back and enjoy the “fruits” of your labor!

Beth Grem grew up in Bucks County, PA and moved to the La Plata area in 1994.  Although her full time job is as an Aerospace Engineer at Patuxent River NAS, her passion is growing vegetables both indoors and out and experimenting with new techniques to push the boundaries of how and where vegetables can be grown.

She became a Master Gardener in 2006 and earned a Horticulturist Certificate from the University of Guelph, ON in 2009. Current interests include growing vegetables both hydroponically and in self watering containers, growing heirloom tomatoes and raising vegetables year round indoors under fluorescent lights.