Tree tomatoes or tamarillos are as easy to grow as some tomatoes. Perhaps this is due to their close relation to tomatoes. Tamarillos are Solanum betaceum, whereas tomatoes are S. lycopersicum.
The name tamarillo was chosen by a New Zealand marketing board. In Spanish it is a tree tomato, tomate de árbol.
The tree has large heart shaped leaves with the texture and colour of tobacco leaves. Tobacco is also a close relative. The flowers are borne close to the stem and look like tomato flowers in form, but are larger and pale pink. The tree is self fertilizing.
Tamarillos originate in the Andes, mainly within tropical latitudes. Because of the cooler mountain climate it prefers a subtropical climate, with a high rainfall of 600-4000 mm and mild temperatures between 15 and 20 degrees C. It is intolerant of frost and drought stress (sourced from Wikipedia). Perhaps these reasons, rather than any soil requirements are why it is not doing well in the Cape summer which is regularly well over 20 C and bar one swift exception, rainless for the past 4 months.
In hot tropical countries it is successfully grown in the highlands, and does not fruit well in the lowlands.
The sun here in Cape Town is very strong, and in the tropics where tamarillos are native it is even stronger. I presume they would really need to be in a spot with lots of sun all day in any region with weaker sun. They don't seem to thrive in shade or semi shade.
The morphology of the two tamarillos I planted diverges a lot. The one which had late morning sun and shade for the rest of the day was markedly different to the one that got sun for most of the afternoon. The shaded sapling was a deeper green, with smaller leaves, and is only a meter tall at present whereas the tree that got more sun is two meters tall and has its first fruit, eighteen months after sowing. The fruit will, however, take half a year to ripen on the tree.
From my experience they do indeed need a lot of water, and will wilt if not watered every day. However our tree soon recovers from wilting. When the rains return I will see if it recovers from the summer, or if the decline it has gone into after bearing is permanent. I have not added any additional feeding and it is recommended by the gardening experts that they be fed three times in summer.
The tree can grow up to five meters under favorable conditions. Fruiting, as you will see with my tree, starts in the second year, but is best from the fourth year. The tree is short lived, around 12 years.
Tamarillo or tomate de árbol.are very popular in South America and I will look there for recipes based on millennia of experience that show an appreciation of the nuances of its rather peculiar flavor.
Collect the seed from an overripe tamarillo by spooning it out of the fruit. Choose fruit that are very tasty, or have the desired characteristics you wish to reproduce. I placed the pulp with seeds in a jar with a little water and fermented it for three days to make cleaning easier, but other people just wash the seeds. It will ferment by itself, there is no need to do anything. Then you can either dry the fruit out or sow them in a tray immediately.
Moisten the soil in the tray. Then scatter the seeds evenly and cover them with 3 mm of potting mix. Cover the tray with plastic to keep the soil moist, or spray the soil in the tray every day. You need a little patience, the seeds can take 7-8 weeks to germinate when the weather is cool. I sowed them in our mild autumn, in April. When they do come up the first two leaves look very like tomato seedlings, but they soon develop their broader, characteristic leaves which are very different to tomato leaves.
Tamarillos germinate very well and you may be thrilled by the idea of having so many and giving them away or selling them. However, you will need to transfer them from the
tray to their own pots very soon. This is more urgent than with a
vegetable because the tamarillo is a rapidly growing tree and it will
become stunted by growing in crowded conditions and very likely
become sickly and die from fungal disease and blight.
I planted the tamarillos from the tray into individual pots with sand, to which I added some vermicast and compost.
I lost about 90% of my seedlings between the tiny six leaf and the arm length stages of growth. This was largely due to an overestimation of their drought hardiness, and the attentions of the garden mollusc. Germinating the seeds is one thing, getting a large healthy viable seedling is another.
When the seedlings were the length of my forearm, I planted them out in the garden. Those I did not plant out withered away.
They are not high maintenance. It is getting all trees to maturity which requires consistent watering and adding teas and vermicast, and repotting when they stall in growth or appear not to be thriving. For instance, a week or two of negligence with watering will negate all your hard work and the trees will not recover. Regular care may be needed for a year. They need to remain strong not to succumb to blights and the snails are their worst enemy, denuding a sapling in a pot in one night.