Florida Fruit Geek

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 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

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.

‘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.

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’

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.

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

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

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:

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.

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#fig #Ficuscarica #nematoderesistantfigrootstock #Moraceae #grafting