This post is to document my results from a community experiment on the effects of grafting on cold hardiness. Results will be updated as the experiment unfolds over the next couple seasons (assuming the plants survive this winter). The experiment is outlined in this post on OurFigs:
The hypothesis is that grafting a moderately cold hardy variety to a very cold hardy variety will make the moderately cold hardy variety more cold hardy. In the experiment I planted 1 Nero 600M (moderately cold hardy), 1 Florea (very cold hardy), and one Nero 600M grafted to a Florea tree. I did this at two locations, one at my house in NJ near Philadelphia (zone 7A) and one at my parents’ house on the Eastern Shore of Virginia (zone 8A).
Planting
Here are the three plants that went in the ground in NJ on April 13, 2019.
Nero 600M
Nero 600M on Florea
Florea
From left to right: Nero 600M, Nero 600M on Florea, Florea.
These were planted in my yard in an open spot (some of the brush behind the plants in the pictures was removed later this spring). They get sun for about 10 hours a day in the summer. Plants are about 3 feet apart.
The other set of plants went into the ground in VA on April 27, 2019.
In VA the plants are planted in an open field getting sun from nearly sun rise to sun set. Plants are again about 3 feet apart.
Summer 2019
Over the summer the with Miracle Grow every two weeks per the original post. The ones in VA were fertilized with a time release fertilizer similar to Miracle Grow since I was not able to visit them every two weeks. Fertilization was stopped on both in July. The plants in VA were on a drip irrigation system while the ones in NJ were watered by hand when needed.
In NJ the growth of the three plants varied significantly in the first season despite all three being similar size on planting. The Nero 600M and the Nero 600M on Florea grew well while the Florea took a long time to get started and only put on a little bit of growth.
In VA all fig trees seem to grow more slowly in their first 2-3 years in ground. These three were no exception and grew only a minimal amount.
Interesting side note, the Nero 600M in NJ that was not grafted developed spade leaves on two of the branches after putting out some more typical deeply lobed leaves.
Fall 2019
Unlike the rest of my in-ground trees in NJ, these have to deal with the cold on their own. The start to the winter was not a good one for uncovered trees. After a handful of 30-34 degree nights that were not enough to put the trees fully to sleep we had a night in the mid 20’s, which may well have damaged a lot of the unlignified wood. We will see in the spring.
Winter 2019/2020
Overall it was a pretty easy winter for figs this year. We had less than 10 nights that fell below 20 F and the lowest low was 12 F in NJ. In VA there were 2 nights below 20 F and the lowest low was 18 F.
Spring 2020
Perhaps because of the fairly quick transition to cold weather in the fall or something else, none of the trees in VA or NJ survived above ground. All six died all the way back to the ground. All six are also growing back from the below ground nodes, but both of the Nero 600 M grafts died completely.
So unfortunately my two trials will not be of much use to determine if grafting imparts cold hardiness. Future ideas for a trial are welcome since I think this is a good hypothesis to test.
