Fig nematode resistant rootstock project, 2019 status report

A fruit of ‘LSU Scott’s Black’ fig from a plant grafted onto the nematode resistant rootstock which I am calling ‘Ficus Echo’ (probably Ficus sycomorus). My project is to pair the best-tasting, most well-adapted fig varieties in Florida to the Ficus species which do best as rootstocks in this area.

My project to test out various Ficus species as potential nematode-resistant rootstocks for edible figs has made slow but steady progress in 2019. Root-knot nematodes are one of the biggest challenges in growing figs in Florida and other warm climate regions around the world. I am trying to acquire every Ficus species that’s reported to be nematode-resistant and graft-compatible with edible fig, Ficus carica, and test them as rootstocks.

One challenge in this project is that while the scion, Ficus carica, can handle hard freezes, many of the Ficus species I am working with as potential rootstocks are tropically adapted, and can’t handle temperatures much below 32F (0C). If freezing temperatures kill the portion of a rootstock below the graft union, that will kill the scion as well.

The scion-rooting issue. Most of the Ficus species I am working with as potentially nematode resistant rootstocks are tropical, and do not handle freezing temperatures. So I am grafting low, and and once the graft has healed I cover the graft union with soil and/or mulch. In many cases, the scion sprouts out roots when I do this. Here I grafted an ‘Alma’ fig onto ‘Ficus Echo’ (probably F sycomorus). That rootstock is on the right, graft union is near the tip of my index finger. The fig scion has sprouted out that big root on the left, just above the graft union. I don’t know if leaving this will cause the plant to let the grafted rootstock die off. I might leave it to see what happens.

The way I’ve dealt with that issue is to graft low on the rootstock, and bury the graft union (sometimes the graft union is right at the soil surface, covered loosely with mulch). When planted this way, frequently the scion sprouts out roots above the graft union. I’m not sure what the long term result will be. Possibly over time this could cause the tree to let the grafted root system die off, preferring its own roots, in a manner analogous to the way that letting suckers from below a graft union can cause a tree to let a scion die off. Possibly it could depend on whether there are in fact root knot nematodes at that planting location, attacking any roots the scion tries to send out from above the graft union.

If this issue turns out to be a major problem when fig graft unions are buried, it might be necessary to keep the graft union above the ground, and be diligent every winter about wrapping the portion of the tree trunk between soil and graft union with some sort of freeze-protective material. Or the tropical Ficus species might turn out to be practical as fig rootstocks only in areas not subject to freezing temperatures.

Here is a list of the Ficus species I am experimenting with. I have given some of them clonal names, because Ficus species can be tricky to identify. in the past, some of the plants I’ve acquired with species names have turned out to be misidentified. If I am anything less than 100% sure of a species ID, it’s safest just to name that clone based on where I acquired it. Also, varieties of some Ficus species might vary in how well they perform as rootstocks, so keeping track of different clones witin a species might help to keep track of those differences.

 

Ficus ‘Echo’, probably Ficus sycomorus

This is the one I got from Echo in Fort Myers. I’m calling it ‘Ficus Echo’ until I can definitely ID it (probably it’s Ficus sycomorus). This Ficus definitely makes a nematode resistant rootstock for figs, but it is frost sensitive.

I obtained this species many years ago from ECHO, the outstanding nonprofit organization in North Fort Myers, where they have used it as a fig rootstock. (Note: in a previous post, I called this accession Ficus glomerata/racemosa, which is the name I was told it was when I got it. I’ve since found out it’s probably Ficus sycomorus, and I’ve added a note to the effect to the original post.) 

This one definitely is both graft compatible with figs and is nematode resistant, and can make a good rootstock for figs over the long term. Echo had a mature fig tree grafted on this rootstock which I photographed in 1998, and I’ve heard that the tree is still there, still producing. I know of one ‘LSU Scott’s Black’ fig tree grafted on this rootstock which was planted out around 2016 in Gainesville, and it is doing well.

‘Ficus Echo’ is extremely frost sensitive – temperatures just a few degrees below freezing will kill it to the ground. This is not much of a problem in the southern part of the Florida peninsula, but in central and North Florida it definitely poses a challenge, as I described above.

In 2018, I planted out an ‘Alma’ fig grafted on ‘Ficus Echo’. It has grown slowly. In 2019, I planted out three more figs grafted on this rootstock: ‘Celeste’, ‘LSU Tiger’, and ‘LSU Purple’. The ‘LSU Purple’ fig has grown rapidly, while the others have been slow growing so far.

‘LSU Purple’ fig grafted onto Ficus Echo (which is probably Ficus sycomorus). This plant was less than knee high when planted out in early summer, photo taken in December.

‘Ficus Echo’ seems to be effective as a nematode-resistant rootstock for figs for South Florida and other areas not subject to freezing temperatures. For areas prone to freezes, it’s less clear if this can be a good rootstock over the long term.

‘Ficus Echo’ propagates readily by cuttings. I usually have lots of this rootstock. I don’t ship it, but contact me if you want to come by my place and get cuttings of this one. Frequently, there’s so much that you could fill a truck bed with trimmed branches to use as cuttings.

 

Ficus pumila

Ficus pumila has two different growth phases, juvenile and mature. It’s often grown as an ornamental in its juvenile phase, when it grows is a thin-stemmed climbing vine, covering walls like ivy. In its mature phase, the stems get much thicker, making them easy to graft. It’s possible to root cuttings from the mature phase, and graft figs onto them.

Fig, probably ‘Southern Brown Turkey’, grafted onto Ficus pumila. I’ve grafted several figs onto this rootstock, and they all seem to show a curious pattern: the plant sends up one or more “normal” upright stems, but also sends out from just above the graft union some densely branching stems with profuse numbers of figs. It seems like there is some kind of dwarfing effect happening with this rootstock.

Ficus pumila can take at least some frost, meaning the graft union does not need to be buried in my area of North Florida.

I have only done a few of these grafts. One of them planted out in the ground grew for a year and then died – both rootstock and scion. I don’t know if the cause of death was related to the graft. I have two others, one in a pot, the other in the ground. Both are showing a similar pattern of putting out dense growth, low to the ground, fruiting heavily. I had speculated that this species might function as a dwarfing rootstock for figs, and this very preliminary evidence indicates this might be the case.

Ficus pumila is listed as cold hardy to 20F, so in areas where winter lows stay above that temp, figs could be grafted above soil level on this species.

In the nursery trade, there are hybrids between Ficus pumila and Ficus carica available. I want to get some of these plants and test them as rootstocks.

 

Ficus palmata ‘Icebox’

Ficus palmata ‘Icebox’

I acquired a plant of Ficus palmata ‘Icebox’ from Plant Delights Nursery in 2018. This clone has turned out to be a little tricky to propagate by cuttings – I’ve gotten maybe 25% success on cuttings of it, compared to close to 100% on some of the other species. But that attempt did result in a few successfully rooted plants, and in early 2019 I grafted ‘LSU Tiger’ onto one of those, and planted it out in the ground in early autumn. The plant has grown rapidly.

‘LSU Tiger’ fig grafted onto Ficus palmata ‘Icebox’. This was planted out in early autumn 2019, but it still managed to about triple its size by December when I photographed it.

Apparently Ficus palmata can handle at least some frost, and cold tolerance might vary from one clone to another. The ‘Icebox’ clone reportedly came from a high elevation population which might have particular frost tolerance. In the coming winters, I should be able to establish how much cold this can handle.

Just to be safe, for the one fig I have grafted onto this rootstock so far, I grafted low and buried the graft union when I planted it out in the ground. If this rootstock clone turns out to have significant frost tolerance, it might be possible to graft higher, above the ground, preventing the scion from establishing roots.

 

 

Ficus ‘Bat House’

This is a Ficus growing in the Ethnoecology Garden near the Bat House at the University of Florida in Gainesville. The plant resembles Ficus palmata, which is supposed to be nematode-resisistant and graft-compatible with edible fig. I propagated numerous plants of this one by cuttings, and tried grafting figs onto them. Some of the grafts took, but they were weak. They made very little growth, and eventually died after a few months. At this point I am thinking this is probably not Ficus palmata, but some other Ficus which is only weakly graft-compatible with Ficus carica. I will try a bit more grafting onto it, but if not successful, I will probably discard this one. I gave plants of this to a few people – if you got a Ficus plant labeled ‘Bat House’ from me, and if you’ve tried grafting figs onto it, please let me know what results you got – either good or bad.

 

Ficus ‘Shadowood’, probably Ficus racemosa

This one came from a packet of seed that was labelled Ficus racemosa. I got it from Shadowood Farm, so for now I am calling it Ficus ‘Shadowood’ pending positive ID.

In 2019, I acquired this one from Nathaniel at Shadowood Farm in Palm City, Florida. Nathaniel had ordered the seed from a vendor in India, who was selling it as Ficus racemosa (which is formerly known as Ficus glomerata). Nathaniel did one fig graft onto this species, which was doing well at the time of my visit in mid 2019.
The original plant I got has grown considerably, and it turns out to propagate extremely well by cuttings. I have a couple grafts I’ve made onto plants of this, too soon to tell how well they’re doing.

This species is definitely tropical, and will require a buried graft union in frost prone areas.

 

Ficus opposita

This grew from a packet of seed labelled Ficus opposita.

A 1925 report from the Florida State Horticultural Society reported that figs successfully grafted onto an unknown Ficus species from Australia, and grew and fruited very well on that rootstock. I posted on Tropical Fruit Forum in 2015, asking if anyone might be able to identify which Australian Ficus species the 1925 report was referring to. The ensuing discussion over the next three years on that thread indicated the species in question was most likely Ficus opposita.

In Australia, some nurseries reportedly are using this native Australian species as a rootstock for figs today.

So in 2019, I ordered seeds of Ficus opposita from Australia. It took a couple of tries, but I finally got a packet of seed in the mail, and out of the hundreds of seeds, two seedlings germinated, one of which promptly died from damping off. The remaining seedling survived. That plant has grown well, and I’ve gotten a first few cuttings from it (seems to take well from cuttings.) I’m looking forward to trying to graft figs onto this one.

 

Other Ficus species:
Someone in the Phillippines commented on one of my previous posts, saying in that country they use Ficus septica, Ficus pseudopalma, and Ficus ulmifolia as rootstocks for edible figs. I don’t have any of those species yet, but I’d like to try them.

 

Grafting technique:

One grafting technique I am experimenting with is to cleft graft fig scions onto branches of tropical, nematode resistant Ficus species. Once the grafts have taken, I will trim those branches and root them as cuttings to hopefully get plants with a graft union low enough to easily protect by covering with soil or mulch.

I propagate all these Ficus species by rooting cuttings, and I’ve been experimenting with a variety of methods of grafting figs onto them, including budding, cleft grafting, and side grafting. I’ve had mixed results. As described above, on the tropical rootstocks, it’s important to graft low, and if I try grafting low onto a rooted cutting and that first graft attempt fails, it can be difficult to do another low graft on the same plant. One technique I am experimenting with to deal with this is a technique I heard has been used by legendary Florida plantsman Crafton Clift. In this method, I cleft graft twigs of edible fig onto outer branches of a rootstock plant. For grafts that are successful, I can then cut them off below the graft and root them as cuttings. By cutting only a few inches below the graft union, it should be possible to produce plants with a graft union very low, for easy protection from winter cold in the resulting tree. So far I have succeeded in getting some of these grafts to take, but have not tried rooting them yet. One concern with this method is that if any of the fig varieties are virus infected, this method could infect the rootstock plant which would then infect any subsequent fig grafts placed on it. So for good plant hygiene, I have put a number of Ficus Echo plants in seven gallon pots for use in grafting this way. Each rootstock plant will be used for grafts of just one accession of Ficus carica, to avoid any possible virus transmission.

Occasionally I hear about other people working on Ficus species as rootstocks for figs. Very few of these projects appear to have been described in a place online accessible to search engines. If you are working on this, I encourage you to get in touch – either leave a comment on this post, or send me a direct message. And I encourage you to post about your work in a place accessible to search engines.

Explore related posts on this blog:

#fig #Ficuscarica #nematoderesistantfigrootstock #Moraceae #grafting


2 thoughts on “Fig nematode resistant rootstock project, 2019 status report

  1. Ignoring all of the cold sensitivity issues, what is the takeaway on the nematode resistance? Is your echo variety the only one that you have confirmed nematode resistance on? What about pumilla and palmata, are they nematode resistant as well? Has that been confirmed? And what are you doing to confirm nematode resistance? Are you just observing growth traits of the plant, or are you digging up the roots and looking for galls? I have talked to you before, my name is Mike and I grow Figs in Tampa. So I am not as concerned with the cold sensitivity, but absolutely concerned with the nematode resistance. By the way, good work here. It is great to see that someone is putting that much time into this issue.

    Liked by 1 person

    1. Hi Mike, good to hear from you again.

      All the species I’m working with are ones that have been reported to be both nematode resistant and graft compatible with common fig.

      My plan is to plant out all accessions side by side in an area which I know to be nematode infested, let them grow for a summer, and dig them out to check the roots.

      The two types that I’ve had for the longest are the Ficus sycomorus ‘Echo’ and Ficus pumila, and I’ve checked the roots of plants of both of those growing in the ground.

      Ficus pumila roots showed no nematode galls at all.

      Ficus ‘Echo’ roots showed very minor nematode galls on widely spaced locations on the roots. Also, several years ago I planted a Ficus Echo in the ground right next to two plants of what I thought was Ficus palmata. The two supposed palmata plants steadily declined after being planted out, and when they were near death, I pulled them out and found the roots were completely riddled with nematode lesions (that accession was definitely not palmata, I’m not sure what it was). The Ficus Echo plant right next to them was thriving, and continues to grow vigorously to this day. So it definitely can thrive for years under heavy nematode pressure.

      The other Ficus accessions mentioned in this article are newer, and I have not yet examined roots. I planted out in the ground plants of Ficus palmata ‘Icebox’ and Ficus racemosa ‘Shadowood’ in early summer of this year, intending them as mother plants to take cuttings from. They both grew vigorously. I might try digging around those plants to check roots, in advance of the experiment I mentioned.

      Ficus opposita is the most recent aquisition, and I have not gotten any of those in the ground yet.

      Liked by 1 person

Leave a Reply to Mike Allen Cancel reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s