Would you like to grow an eggplant tree, yes you heard right, a tree, that can produce dozens of eggplants, and not die down in winter?
Well, you can if you graft eggplants (or tomatoes) onto a perennial Devil Plant rootstock. In this article (which is probably one of the most comprehensive articles on the internet on the subject of grafting devil plants) we’ll explain how this is done.
Devil plants are used as a rootstock to graft onto because the plants are very vigorous, with a stronger root system, allowing the plant to support more fruit and tolerate diseases that affect the root system of eggplants and tomatoes. In a warm climate or in a greenhouse (or appropriate cover) in colder climates, the plants will produce eggplants year after year.
About the Devil Plant
They say the devil is in the details, and with devil plants, there are some details we need to consider – namely what exactly is a devil plant?
When people refer to “devil plants” for eggplant grafting, they may be referring (or indeed using) any of the “devil plants” in this family – Devil’s apple (Solanum capsicoides), Devil’s fig (Solanum torvum) or Giant devil’s fig (Solanum chrysotrichum).
All devil plants are members of the Solanaceae (nightshade) family of plants, which also includes tomato, potato, eggplant, chilli peppers, capsicum, tobacco, petunias and many others. That’s why you can graft eggplants and tomatoes onto them, because they’re related.
The Devil Plant (Solanum capsicoides) is a native of South America and grows as a perennial bush or small tree up to 3m high. the botanical name Solanum aculeatissimum is used to describe Solanum capsicoides, which also goes under the names of Cockroach berry, Indian Love Apple, Soda Apple, Devils Apple and Devil Plant.
Devil’s fig (Solanum torvum), commonly known as turkey berry, prickly nightshade, or wild eggplant is a erect perennial shrub, 0.8–2.5 m high, native to the West Indies, which has spread to many countries with tropical climates. it is a short-lived perennial, it is reported that .most plants live about 2 years. The fruit are used in Thai, Jamaican Lao and Indian cuisine.
There can be disagreement regarding the identification and botanical classification of devil plants. The Giant Devil Fig Solanum chrysotrichum has been previously wrongly classified as Solanum hispidum. It’s a shrub or small tree to 4 m which is native to tropical Central America.
All of these devil plants have been used around the world to graft eggplants and tomatoes onto, so use these varieties, they are tried and tested. Do not select random wild solanum family plants to graft onto!
How sound is this technique?
Doing some research, I found an article published by the Queensland State Government, Department of Agriculture, Fisheries and Forestry – “Grafting eggfruit to control bacterial wilt” (Source: http://www.daff.qld.gov.au/plants/fruit-and-vegetables/vegetables/other-vegetable-crops/grafting-eggfruit-to-control-bacterial-wilt)
They in fact recommend grafting eggplants on to a resistant devil plant rootstocks to avoid the problem of bacterial wilt which is a major disease of eggplants.
Here’s an extract from the article:
A rootstock that can be used in eggfruit grafting is devil’s fig (Solanum torvum), the fruit of which is used in Indonesian and Thai cooking. Devil’s fig is quite resistant to bacterial wilt (Ralstonia solanacearum); however, it has shown wilt symptoms when planted through plastic mulch, due to the higher soil temperature under the plastic.
Other possible types of rootstock are giant devil’s fig (Solanum hispidum – beware the thorns) as well as wild tobacco tree (Solanum mauritianum). Although not included as part of the trial, these may be good options if their resistance to wilt is as good as devil’s fig. The amount of suckering from these plants is unknown. Devil’s fig tends to be more adaptable to different soils in the wild than the other two.”
They are a State Government, Department of Agriculture and they’re suggesting to farmers that Devil’s fig (Solanum torvum), Giant devil’s fig (Solanum chrysotrichum) and wild tobacco tree (Solanum mauritianum) are suitable as rootstocks for grating eggplants onto. So there you go!
Identifying the Different Devil Figs
How do you distinguish a devil fig from a giant devil fig? Here is an extract from a government source which explains the difference.
Devil’s fig (Solanum torvum) is very similar to giant devil’s fig (Solanum chrysotrichum). These two species can be distinguished by the following differences: devil’s fig (Solanum torvum) has moderately large leaves (usually 5-21 cm long) with several (about seven) slight to moderately deep lobes. Its relatively small white flowers (up to 25 mm across) have small sepals (3-4 mm long). The dense star-shaped (i.e. stellate) hairs on its new growth are whitish or yellowish in colour.
Giant devil’s fig (Solanum chrysotrichum) has moderately large to very large leaves (usually 9-35 cm long) with several to numerous (seven to thirteen) moderately deep to very deep lobes. Its relatively large white flowers (30-40 mm across) have relatively large sepals (7-10 mm long). The dense star-shaped (i.e. stellate) hairs on its new growth are reddish in colour.
Put simply, the easiest way to tell them apart is that Solanum torvum has white or yellow hairs on the new growth, while Solanum chrysotrichum, whose species name “chrysotrichum” is ancient Greek for “gold hair”, which is rather misleading, actually has reddish coloured hair on new growth.
Devil Plant Alternatives
If you can’t get find a devil plant, there are a few other Solanaceae family of plants you can use instead.
For those who would prefer to use a native plant rather than an exotic, Solanum aviculare, commonly called kangaroo apple in Australia, poroporo or New Zealand nightshade in New Zealand , is a relatively short-lived perennial shrubs, with a life expectancy of 5-6 years in good conditions. It is native to New Zealand and the east coast of Australia. It will work well as a rootstock for grafting eggplants, and you shouldn’t have any trouble finding this in Australia or NZ, as it’s a native plant. It’s own fruit are edible, but only when they’re completely ripe, their poisonous when unripe.
Solanum mauritianum, commonly known as wild tobacco, tobacco bush, tobacco weed, kerosene plant, ear leaf nightshade, woolly nightshade, flannel weed and bugweed, can be used to graft eggplant or tomato onto. This is a small tree or shrub native to South America, including Northern Argentina, Southern Brazil, Paraguay and Uruguay. It has spread to Australia, Azores Islands, Cook Islands, Fiji, Hawaii, India, Madagascar, Mauritius, New Caledonia, New Zealand, Norfolk Island, Réunion Island, Solomon Islands, Sri Lanka, Tonga, and several southern African countries, so if you live in any of these locations you may be able to find it growing wild.
The Devil Plant as a Grafting Rootstock
It’s called a Devil Plant because it really is a “devil of a plant” to work with if you’re not careful! The stems, branches and the main veins on the underside of the leaves have stout, broad based, hooked spines (see pictures below)
Our interest in the Devil plant is to use it as a rootstock to graft eggplants (Solanum melongena) on to. This is a popular practice with Europeans, including the ones living in Australia.
It’s also used extensively in China on a commercial scale. Here is an extract from the research article "The History, Current Status and Future Prospects of Vegetable Grafting in China" by Y. Huang, Q.S. Kong, F. Chen and Z.L. Bie, College of Horticulture and Forestry Sciences, Huazhong Agricultural University/Key Laboratory of Horticultural Plant Biology, Ministry of Education, Wuhan, China
“In China, the earliest literature about vegetable grafting was recorded in an ancient book "Fan-Sheng-Zhi-Shu" in the first century, BC. However, commercial application began in 1970s and increased with the rapid development of protected cultivation. The main purposes of grafted vegetable production in China are to overcome soil borne diseases and increase resistance against abiotic stress. Currently, China is the leading producer of cucurbitaceous and solanaceous vegetables across the world. About 40% of watermelon, 20% of melon, 30% of cucumber, 15% of eggplant, 1% of tomato, and 1% of pepper are grafted.”
Looking at the research paper details, in China they graft the following plants to the respective rootstock:
- tomato are grafted onto Solanum lycopersicum (tomato), Solanum melongena (eggplant), S. lycopersicum × Solanum habrochaites,
- eggplant are grafted onto S. melongena (eggplant) and Solanum torvum,
- pepper are grafted onto Capsicum annuum (pepper).
As you can see, the Chinese commercial growers graft some plants onto themselves, as a double rootstock for one plant, and eggplants are indeed grafted commercially onto Solanum torvum. They graft these solanum crops using cleft, slice and tube grafts, and their main purpose of grafting of these solanum crops is for soil-borne disease control, cold tolerance and salinity tolerance
For home gardeners, grafting creates an “eggplant tree” which can literally produce from dozens to hundreds of eggplants according to many accounts I have heard. The only necessity is to cover the grafted tree in winter in cooler climates so the eggplant grafts don’t die off.
The grafting process is relatively simple, you just use basic cleft “V” grafts, and the bits you cut off the Devil plant can be used for striking cuttings to grow new Devil plant, and you can either root the cuttings in water, or in potting mix.
In the southern states of Australia, where the climate is classed as “Cold”, the biggest problem with growing eggplants from seedlings is that the growing season is not long enough. They take most of Summer to produce their first crop, then it gets too cold, and no successive crops are produced. By grafting to create an “eggplant tree”, you can produce eggplants for about eight months of the year for two or three years.
Now that we’re familiar with the plant, lets get grafting!
Before I go into describing the process of grafting eggplant onto the Devil plant, it’s probably a good idea to quickly cover some basic horticultural concepts.
What is Grafting?
Grafting is the practice of joining the living tissue from one plant to that of another plant that is either the same species or closely related, so that they will fuse together to form a single plant.
There are many grafting techniques, and here we will learn how to perform a Wedge or Cleft graft, sometimes referred to as a “V” graft. It’s one of the simplest grafts, it has a very high success rate and can be done with very basic tools.
Wedge or Cleft Graft
In grafting, the plant that you are grafting onto that has roots is called the rootstock.
The cutting or branch that is grafted onto the rootstock is called the scion (pronounced sahy-uhn)
The basic procedure is as follows:
- The scion is prepared by making two sloping cuts at its base to form a wedge 2.5 to 3 cm long (depending on how thick it is).
- The rootstock is pruned at the desired height (if grafting to top) or its branch is pruned part way (if grafting to branch) and a clean edged cut is made down the centre of the stem for about 3 cm.
- The scion wedge is inserted into the rootstock, with one or both edges lining up perfectly to match the cambium layers* (If the scion wedge has a thicker side, match the edge on this side).
- The union is tied firmly with grafting tape to seal the union, and to prevent moisture loss, and to stop scion movement.
* The cambium is the thin green layer of tissue located just beneath the bark, between the bark and the wood, and is a layer of actively growing cells which produce the wood, bark and vascular tissue of the plant. In making a graft the object is to place the cambium of the scion in close and firm contact with the cambium of the rootstock by accurately lining up the outer surface, then binding it carefully so it doesn’t move. The cuts to scion and rootstock must be made with a very sharp, clean blade to obtain a flat, clean surface and minimise damage to the tissues.
How To Graft the Devil Plant
Step 1. Gather Required Materials
Now, you won’t need all these things to perform a graft, as some are optional, but you will need most of them.
On the left hand side, from the top down:
- Grafting Tool or Small Craft Knife or Grafting Knife (use any one of these)
On the right hand side, from the top down:
- Plastic bag and wire tie
- Clothes Peg
- Strip cut from thick plastic bag, about 50cm long and 1.5cm wide, or grafting tape (use any one of these)
- Piece of shade cloth
Step 2. Prepare the Scion
Select your eggplant for grafting, and using secateurs cut a tip or branch about 5-10cm long to use as a scion.
Here is a pruned tip of an eggplant ready to prepared as a scion
Cut away all the large leaves from the scion, leaving only small leaves and buds.
This prevents moisture loss and increases the chances of the graft surviving.
Now you’ll need the grafting tools for cutting the wedge shaped end of the scion.
Pictured below is a grafting knife and an automatic grafting tool.
Any sharp, clean knife will do the job, and a small cheap craft knife (the “Stanley knife” style with snap off blades) shown on the right works very well.
The scion is prepared by making two sloping cuts at its base towards the end to form a wedge 2.5 to 3 cm long.
Completed scion with “V” or wedge shaped end.
In case you’re wondering why use a dedicated grafting tool, well, I’ll tell you. It makes precise, exact matched cuts that fit together perfectly, that’s why!
And furthermore, if the grafting tool has a “keyhole” or “omega” blade, then the scion and rootstock can be cut to “key” together like a jigsaw puzzle piece, as shown on the scion below.
This luxury will set you back close to the hundred dollar mark though, and it is a luxury, not a necessity…
Step 3. Preparing the Rootstock
Using secateurs, cut the branch you wish to graft to at the desired length, remove the spines where you intend to graft (to prevent injury to your fingers!) if you like, and remove any leaves from the branch.
Using a grafting knife, make a split or "cleft" through the center of the stock and down 2.5 to 3 cm to match the wedge on the scion.
Step 4. Insert the Scion
Insert the scion into the split or cleft in the end of the rootstock branch. The cambium of the scion should contact the cambium of the rootstock. If the rootstock is thicker than the scion, then just line up one side.
If you find that the rootstock is too hard or woody to open up, you can cut a very thin wedge out of the end of the rootstock that is smaller than the wedge on the scion, then use the knife to pry it open while you push the scion into it.
Step 5. Bind the Graft
Secure the graft tightly with grafting tape to prevent moisture loss and to stop the graft from drying out.
Make sure that the grafting tape is wrapped tightly around the graft join, and extends over part of the rootstock and scion to make an airtight seal.
If you don’t have grafting tape, you can cut strips from a sturdy plastic bag, which is what I have used here. I get the same success rathe as I do with proper grafting tape. The strips need to be about 50 cm long, and I cut them about 1.5 cm wide. Remember that a bag is doubled, so when you cut across a 25 wide bag, you get a “loop” which is 50cm long when you make a cut in it.
The success rate of grafting will be greatly enhanced if the newly completed graft is covered with a small plastic bag and tied on the bottom with a wire tie to allow both a build up of heat and humidity.
I add a few drops of water in the bottom to increase humidity, and get a bit of air inside the bag before tying it off, so the bag isn’t hanging off the scion. I’ve also found that tying one corner of the bag to a higher branch lifts it up so it is not draped over the graft.
If the plant is in a shaded greenhouse, then it will be fine, but if it is exposed to the sun, then the graft will need some shading otherwise the scion will get steamed and cooked in the plastic bag.
Some prefer to place a small brown paper bag over the plastic bag to prevent excessive heat build up, but my preference is to use a small piece of shadecloth to let some light in.
Just simply fold a piece of shadecloth around the bag, and fasten it with a clothes peg. If you have multiple grafts, you can place one larger piece of shadecloth over all of them at once.
Step 6. Removal of Bags and Grafting Tape
With a eggplant graft to a Devil plant, I have found that I can remove the plastic bag after one week.
The grafting tape can be left on until the grafts show some decent growth, which can be over a period of a few weeks. If left on too long (months) the tape may restrict growth by becoming too tight n the graft area.
In a few weeks the grafts will flower and fruit, prolifically!
A Few Afterthoughts…
All the grafting pictured was carried out mid-summer, because that’s when my eggplant seedlings were large enough to take cuttings from. I have carried out about a dozen eggplant grafts on the one Devil plant, and they have all taken successfully. Tomato can also be grafted on to the Devil plant, and you can have both eggplants and tomatoes grafted onto the same tree too. There’s nothing like experimenting to see what works. I’ve even added two cherry tomato grafts, and they worked out too. I’ll need to figure out how to cover the plant for winter, and what to use to protect the grafts from the cold.
This grafting process make plants that are annual in cold climates into perennials. I have seen tomatoes grafted onto Devil plants in greenhouses fruiting almost all year round, and I have seen outdoor eggplant grafted Devil plants survive a winter and fruit for their second year here in Melbourne, Victoria. So yes, it really works! This will definitely change the way you grow tomatoes and eggplants…
… and one final thought on perspective, ethnocentrism and respect for other people’s cultures
I have updated the content on this article and in response to previous comments, have added this section.
To those thinking about posting about the ‘weed’ potential of the devil fig, please note THIS IS AN INTERNATIONAL WEBSITE (with the majority of readers outside Australia!), please be mindful that what plants may be indigenous or native to your area may be a ‘weed’ elsewhere, it works both ways. For some readers this is a discussion of their native plants, plants that form part of their native cuisine or traditional medicine. Grafting eggplants onto devil plants is a commercial agricultural practice in China, and a common practice amongst European gardeners, as well as ethnic gardeners of Southern European origin who live in Australia. Learn to respect other people’s cultures!
Your native plants are someone else’s ‘weeds’ too! A ‘weed’ is not a scientific or biological category or class of plant, it’s a value judgement statement based on human preference – it’s a plant growing where the observer doesn’t like it growing. If we were to write ‘weed warnings’ based on every geographical location’s perspective, EVERY PLANT WOULD HAVE A WEED WARNING!
As responsible gardeners, and mature adults able to make informed and responsible decisions, it is common sense that if plants have the potential to escape from your garden, IT IS YOUR RESPONSIBILITY to contain them, and comply with any legalities of your area!
Secondly, if you’re grafting these solanum rootstocks, all branches SHOULD BE GRAFTED! There shouldn’t be branches producing the rootstock flowers and fruit, you don’t want the plant’s energy going into something you don’t eat, they should be producing eggplants. It’s OK to have some rootstock leaves on the lower branches though.