Grafting tomato and eggplant onto wild tobacco
Tomato, potato, eggplant, tobacco, glossy nightshade and many other common plants are all part of the deadly nightshade family. Because they are so closely related, they can be grafted onto each other. Note that they are also poisonous to various degrees so you should not, for example, try smoking the wild tobacco. Many people have tried grafting tomato onto potato to produce a more useful plant, but apparently the fruit don't taste good and it doesn't produce decent potatoes either. Grafting fruiting plants onto wild tobacco works fairly well. Wild tobacco is a sturdy, long lived tree/bush that can grow to a few meters high. It grows wild around Brisbane and can be a bit of a nuisance. I cut down a large wild tobacco tree that was on the border of my property, and now have smaller ones coming up in my garden beds. The following guide is illustrated with photos from a cherry tomato graft I did recently. I didn't have any suitable eggplant to graft at the time, but the principle is the same. Eggplant may even be more suitable because it grows in a similar manner to wild tobacco. You can graft eggplant, tomato and any other suitable plant onto the same wild tobacco to create an eggplant and tomato tree.
Disclaimer: do this at your own risk. I have eaten three cherry tomatoes from grafted stems (including the one shown in the second picture) and I am still alive, but cannot guarantee the same for you. Toxicity may depend on the exact species you graft onto. Before consuming, try rubbing the juice from the tomato onto the underside of your wrist, then onto your lips, to test for any adverse reaction.
The first step is to find, or grow, some wild tobacco. It is easy to identify because there are few plants with such large leaves. The stems have a thick fuzzy 'hair', especially on young plants. The example shown is a young wild tobacco bush onto which I have already grafted two cherry tomato stems. I allowed two wild tobacco stems to continue growing so that I could graft more onto this bush later. The first step is to find, or grow, some wild tobacco. It is easy to identify because there are few plants with such large leaves. The stems have a thick fuzzy 'hair', especially on young plants. The example shown is a young wild tobacco bush onto which I have already grafted two cherry tomato stems. I allowed two wild tobacco stems to continue growing so that I could graft more onto this bush later.
Step 3: cut a few lengths of electrical tape and stick them onto the wild tobacco bush. You will need these to be handy later on.
Step 4: choose a suitable stem from your tomato bush. The stem should be roughly the same diameter as the wild tobacco stem (where you intend to make the join). This is because the tubes that carry the water to the leaves, and the sugar to the roots, are around the outside of the stems. You want them to lign up as well as you can manage. It can be a bit hard to judge the diameter of the wild tobacco because of the hairy stuff on the stem.
Step 5: Cut the stem and place it in water immediately. This prevents air getting sucked into the tubes and giving your stem an embolism. Cut the stem again at an angle, then again from the other side to give it a wedge, or 'V' shape. Immerse each fresh cut in water and leave it sitting in water when not handling it. Cut most of the leaves off the stem, as it won't be getting much support until the graft takes hold. Leave any new stems that have just started to grow - the ones you would normally break off to maintain the health of your tomato plant.
Step 6: Cut the end off the wild tobacco stem. Make an inverted 'V' cut to match that on the tomato stem. Insert the tomato stem. The photo shows a string tied around the graft. This was just to keep it in place while taking the photo, and was removed before taping. The wild tobacco stem is normally stiff enough to hold the tomato stem in place anyway.
Step 7: Wrap the electrical tape around the graft. Some people recommend against watering the rootstock at this point as it sends too much sap into the join. I have also been told to wrap it in alfoil, put a plastic bag over it to maintain humidity, and put up some shade. I'll give these a go next time and post an update.
Here is a closeup of the two old grafts. A caterpillar was found inside the lower tomato stem some time after grafting. It was removed, but not before it had done some damage. It is still producing fruit. You should continue cutting back the wild tobacco leaves from any other stems as the graft begins to take hold. This forces the wild tobacco to put any water the roots collect into the grafted stems. Do not cut them all off straight away or the wild tobacco will suffer too much.
Unfortunately the grafted tomato plants don't seem to live any longer than those grown the normal way.Len's guide to building a garden from scratch. (Link established under ozpolitic's reciprocal link program).