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How to graft tomatoes

by Stephanie Suesan Smith on March 30, 2011

As I mentioned in my last post, Territorial Seed Company is now selling grafted tomatoes.  According to research being done by Ohio State University, tomatoes that are good to eat can be grafted onto rootstock that is disease resistant and they will grow well and produce more tomatoes than ungrafted plants.  This is important to market growers who often have problems with diseases because they grow large fields of tomatoes year after year.

So how do you graft a tomato?  Very carefully.  First, you grow the seeds out as you normally would, in a greenhouse or your home.  For the rootstock, most people use either “Maxifort” or “Beaufort.”  Maxifort seems to be the better of the two, so I will refer to it as the rootstock for the rest of the article.  It is a good, vigorous grower but produces terrible tasting tomatoes.

You also need to grow plants of the type you want to get tomatoes from.  Many people are growing heirloom tomatoes that are not disease resistant but produce good tasting tomatoes.  When grafted onto the disease resistant root stock, they grow just fine.

The diameter of the rootstock plant and the scion, or graftee, must be the same where the graft is done.  Otherwise, the graft doesn’t heal and the plant dies.  There are three main methods of grafting:  tongue approach, cleft grafting, and tube or Japanese grafting.

With cleft grafting, you start the rootstock seeds 5-7 days before you start the scion.  When the plants have four or five leaves, cut the top half of each plant off.  Make a notch in the top of the rootstock plant.  Trim the bottom of the stem from the scion into a wedge.  Put the wedge into the cleft, gently.  Hold the plants together with a grafting clip.  Other clips either have too much tension or not enough.  Remove the clip in 7-10 days.

Tube grafting is the type of grafting most often done for commercial tomato production.  That is partly because it can be done as soon as the plants are physically big enough for you to handle.  In order for you to do it, you will need to sow your rootstock 1-2 days prior to the scion.

Cut the rootstock at a slant and discard the top.  Cut the shoot in a matching slant and discard the bottom.  Place the two ends you keep in direct contact with one another, being careful to line them up so the tubes that carry water and nutrients to the leaves and energy to the roots match.  Clip together

Finally, the tongue approach involves bigger seedlings in the 14-21 day range.  Cut off the top of the rootstock.  Cut a chunk out of the side of the scion plant, not too deep.  Then insert the end of the rootstock into the chunk.  Clip the plants together.  The scion is still potted, with roots.  In 3-4 days, pinch the stem of the scion below the graft.  Wait another 3-4 days, then cut the bottom stem of the scion off below the graft.

With the cleft and tube methods of grafting, you must place the tomatoes in a fairly dark area and keep them moist so they can heal.  They need around 86 degrees F and 95% relative humidity for optimal healing.  This takes 4-5 days.  The plants must be gradually reintroduced to the regular environment and they are usually in the greenhouse 7-8 days after the graft.

When you get a grafted tomato, or make one, and you plant it, there are some things to remember.  Keep the graft well above the soil or the scion will try to root.  The graft area is fragile, so be careful and stake the tomato.

The bottom line on grafted tomatoes is that if you are not too picky about tomatoes, grow the conventional kind and enjoy the taste of homegrown tomatoes.  If you are a tomato connoisseur, you might buy some grafted tomatoes and see how you like them.  If you fall in love with them, then you can learn to graft them.  Otherwise, unless your livelihood is at stake, it seems like a lot of trouble and expense for not that must gain.

At present, Territorial Seed Company is the only place selling these plants retail.  I have not dealt with these folks, so cannot say one way or another about their service or products.  Let me know if you get some of these tomatoes because I am interested in how they do.

 
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{ 2 comments… read them below or add one }

Laara May 26, 2011 at 12:02 pm

Betterheirlooms website also offers supplies for home gardeners to try their hand at tube grafting. Three thing you need to be really mindful of is to do tube grafts when the seedlings are very small — just a couple of pairs of true leaves — Second, the diameters of the two stems must be identical in size. Third, keep the humidity very high while the grafts heal. You can do this with small numbers of seedlings by placing them inside a tightly closed plastic bag in a dark room or closet. Set the container of seedlings on an outer tray covered with warm water before you close the bag with clips or clothespins to establish a very humid environment. After 4-5 days, gradually introduce them to normal light and humidity over 2-3 days. Good luck with grafting!

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Stephanie Suesan Smith May 26, 2011 at 2:51 pm

Thanks for the information. Sounds like you have done this a lot.

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