Saturday, December 27, 2014

Performance evaluation of grafted tomatoes using rootstock “Supernatural”, in the conditions of home gardening

The experiment was performed in the conditions of a home garden, meaning I had limited space, containers and beds of various sizes, unequal lighting, and other limitations, making the data imperfect. In addition, I had only one specimen of each experimental sample.  Nevertheless, I set out to answer: do I get a better yield from grafted tomato plants? – and the answer is yes. Grafted plants produced more tomatoes. Supernatural rootstock was used for all grafted plants.


A total of 34 plants were analyzed in the summer of 2014 in Davis, California.  22 plants were in 11 pairs (grafted and selfrooted) representing 11 different varieties, planted in the same container or bed, and kept single-stemmed, so I could discriminate the yield between plants in the same container. The other 12 “single” plants were growing in their own pots or beds and were also kept single-stemmed, so their growing conditions are comparable with the paired plants. 7 of them were grafted, and 5 were selfrooted.


I grow exotic heirloom cultivars. Here are some of them from 2012-2013.


I faced noticeable harvest decline in 2013 for some varieties.
Ukrainian Heart and Russian were producing significantly less

The plants were grown in the same pots or beds as in 2012.


Does grafting heirloom tomatoes improve yield?
EXPERIMENT was performed in 2014, in Davis, California

The yield was recorded for 5 months of fruiting period for grafted and selfrooted plants (Harvest from June 11 to November 10)


All paired plants were grown in the same pot or bed and kept as single stemmed plants

The pots used for different pairs could be of different sizes; also, different garden locations differ in the amount of sunlight.

This should not matter when comparing plants from the same pot.


The harvest is recorded in grams per day from each plant.
Two small-fruited cultivar pairs, Blush and Galina, became multi-stemmed in late summer/fall. From this moment, the harvest is recorded per pair, as it was impossible to discriminate the yield between plants in the same pot.  For the comparative analysis, only the data before this point is used. Here is an example.


From 11 pairs
(grafted and selfrooted in the same pot or bed)

55% increase on average for grafted when in pair with selfrooted in the same pot.

From 7 single grafted plants

From 5 single selfrooted plants

114% increase on average for grafted when in its own pot, as compared to selfrooted plants. 


Variety Grafted  Selfrooted
Galina 1,157 1,374
Russian 2,430 469
Blush 1,857 1,159
Pork Chop 2,093 1,608
Pink Berkeley Tie-Dye 2,385 2,084
Cherokee Chocolate 3,669 1,856
Ukrainian Heart 5,873 0
Mother Russia 3,578 2,480
Big Rainbow 4,315 3,491
Cosmonaut Volkov 4,757 3,128
Indigo Apple 2,887 5,001
Average 3,182 2,059
Total 35,001 22,650

9 out of 11 varieties showed a yield increase when grafted.  Only two varieties did not show a yield increase when grafted, Galina and Indigo Apple.


Grafted Grams
Ukrainian Heart 7,669
Mother Russia 3,406
Russian 3,357
Orange Strawberry 3,635
F3 #3 2,751
F3 #5 4,967
F3 #10 2,026
Average for grafted 3,973
Total 27,811


Selfrooted Grams
F4 #11 2,868
F3 #4 1,542
#2 1,858
Orange Bulls Heart 1,736
Sioux 1,283
Average for selfrooted 1,857
Total 9,287

Increased yield in grafted plants may be caused by more than just nematode resistance.  Big Rainbow selfrooted plant did not display RKN infection, but the yield from the grafted plant was 24% higher.

The RKN resistance was  broken  in the rootstock of grafted Cosmonaut Volkov plant, and this grafted plant still produced 52% more  than the selfrooted  one.  This was the only Supernatural root out of 18  grafted plants that showed RKN infection.


20 different varieties and progenies were used in this experiment

Small fruited

1. Blush
2. Galina
3. #2

Medium fruited

1. Indigo Apple
2. Mother Russia
3. Sioux
4. F3 #4

Large fruited

 1. Big Rainbow
 2. Cherokee Chocolate
 3. Cosmonaut Volkov
 4. Orange Bulls Heart
 5. Orange Strawberry
 6. Pink Berkeley Tie-Dye
 7. Pork Chop
 8. Russian
 9. Ukrainian Heart
10. F3 #3
11. F3 #5
12. F3 #10
13. F4 #11


Only Blush showed some yield benefit when grafted.  We liked the taste of Blush and plan to grow it grafted next year.
Galina probably does not need grafting.  I may try to use Galina as rootstock next year. This is an Asian-type tasting tomato, and not everyone liked it.  We liked it a lot and will grow it selfrooted next year.
We will not grow small fruited #2 again because the taste was bland.  The seeds came from tomatoes purchased at a local tomato farm.


Indigo Apple. We liked it a lot, but this variety is not for everyone.  It has a significant smoky flavor.  The grafted plant delivered significantly fewer tomatoes, so I will grow it on its own roots next year.  This variety is not resistant to RKN, but grafting reduced yield for this pair.
Mother Russia.  A very good tomato with a balanced flavor.  I will grow it grafted next year.
Sioux did not perform well, but I had only a selfrooted plant.  I will not grow it next year.
F3 #4 is a green-striped elongated tomato with a smoky flavor.  We liked it, but it is not for the majority of consumers. I will take it to F4 if I have space and time.  I may do grafting.

LARGE FRUITED, yield in grams

Variety Grafted  Selfrooted
Big Rainbow 4315 3491
Cherokee Chocolate 3669 1856
Cosmonaut Volkov 4757 3128
Pink Berkeley Tie-Dye 2385 2084
Pork Chop 2093 1608
Russian 2430 469
Ukrainian Heart 5873 0
Orange Strawberry 3635 N/A
Russian 3357 N/A
Ukrainian Heart 7669 N/A
F3 #3 2751 N/A
F3 #5 4967 N/A
F3 #10 2026 N/A
Orange Bulls Heart N/A 1736
Sioux N/A 1283
F4 #11 N/A 2868


Big Rainbow and Cherokee Chocolate did not show RKN infections 

Cosmonaut Volkov pair had RKN on both plants.  This was the only Supernatural root with RKN (out of 18 grafted plants)

Pink Berkeley Tie-Dye selfrooted plant did not have RKN

Selfrooted plants of Pork Chop, Russian, Orange Bulls Heart, and F4#11 displayed RKN infection. Selfrooted Ukrainian Heart died very early in the summer, and no good picture was taken.  It may have died because of a combination of multiple root diseases.


All large fruited produced more when grafted.  Some varieties did not show RKN infection.  I will grow the selected varieties next year, all grafted.

Variety RKN on self Will grow grafted next year?
Big Rainbow No Yes
Cherokee Chocolate No No, the flavor is just OK
Cosmonaut Volkov Yes Yes
Pink Berkeley Tie-Dye No Yes
Pork Chop Yes Yes
Russian Yes Yes
Ukrainian Heart ? Yes
Orange Strawberry - No, the skin is too hard
F3 #3 - No, the flavor is just OK
F3 #5 - Yes
F3 #10 - No, the flavor is just OK
Orange Bulls Heart Yes Yes
F4 #11 Yes Yes


Most varieties benefited from grafting.  The exceptions were Galina and Indigo Apple.
For paired plants (grafted and selfrooted in one pot), the average yield increase for grafted was 55%.  For various unpaired varieties in individual pots, the average yield increase for grafted was 114%.

The total yield from this experiment was 99.3 kg or 218.7 lb.

94,749 from individual plants
1,783 Blush after Oct 1
2,774 Galina after Sept 2
99,306 Everything up to Nov 10

And here is the daily harvest from all plants


  1. One of the best rootstock tests I have seen. I saw only one reference to the rootstock-supernatural- so I assume you did not try others? How bad was your disease problem before? I have used grafting for a couple years mostly because my plants have survival issues, not exactly sure what happens but my plants get attacked by thrips and maybe bacterial wilt. I plan to keep grafting since it seems to increase plant survival rates. Have you tried saving seeds from an ungrafted root stock plant? Supernatural is one of the only non hybrid rootstocks available so saving seed would cut the cost of grafting.

  2. Thank you. RKN was and still is my main problem. I graft tomatoes I grow in my yard every year. Thanks for pointing out that Supernatural is a stable variety. I have another post here describing a very small experiment with various rootstocks


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