Whanganui gardening: Get tropical in your garden - try tamarillos

Tamarillos are in demand like never before. Photo / Supplied

Gardening has many facets to it. It has a practical or functional aspect that merges into aesthetic which becomes fashion-driven.

A lush, leafy-green tropical and semi-tropical structural look combined with colour is highly desirable at the current time.

I have noted a change with certain plants within these areas, both from a consumer interest perspective and in nursery production. There is increasing availability of palms, bromeliads and succulents included in this trend. There is high interest in growing both ornamental and edible bananas but supply has not yet caught up and they are hard to find.

There is increasing interest in and availability of subtropical fruit plants and more people are starting to grow previously unavailable Cherimoya and Casimiroa. There is unprecedented demand by home gardeners for avocado trees which are available in garden centres for parts of the year. Other favourite subtropical fruits, the passionfruit and tamarillo, are experiencing demand like never before.

The past few winters in Whanganui have been exceptionally mild, with few frosts. This is highly advantageous for establishing cold-sensitive plants such as these.

Tamarillo, or tree-tomato, has long been a favourite of mine. They are always expensive when purchased from the supermarket and only available for a limited time each year. Tamarillo fruit during winter from May to July. This timing makes them a great fruit to grow, as this can be a time of year when fruit and vegetables are more expensive to purchase.

The red varieties tend to be tart and a sprinkling of sugar may be needed. The yellow varieties tend to be sweeter.

Tamarillo plants are fast-growing small trees that fruit in their second year. They reach full production capacity in about four years. They are relatively short-lived; an average tree fruits for about seven to 12 years. They can be propagated easily in the home garden by cuttings or from seed collected from the fruit. Seed-raised trees tend to grow straight up with a single leader that is best chopped to encourage a lower-branching canopy. Cutting-grown varieties seem to have a natural tendency to branch lower down. All tamarillo are self-fertile so you can plant just one plant, though cross-pollination by having more than one plant can increase the crop size. The growth habit is a fast-growing tree with large heart-shaped, soft, hairy leaves. Size: 3m x 2m.

Four tamarillo varieties grown by Incredible Edibles perform particularly well and have good-sized fruit.

• Tamarillo Bold Gold: Clusters of pink fragrant flowers appear in spring within 18 months of planting. Large golden fruit which is sweet and less acidic than the red varieties.

• Tamarillo Teds Red: Clusters of pink fragrant flowers appear in spring within 18 months. Large, almost round, bright red fruit.

• Tamarillo Tango: Clusters of pink fragrant flowers appear in spring within 18 months. Medium-sized red/orange fruit. Very sweet and low acidity. Produced and marketed by Incredible Edibles in association with Plant & Food Research and available in garden centres.

• Tamarillo Mulligan: Clusters of pink fragrant flowers appear in spring within 18 months. Medium dark red fruit inside and out. Full acidic flavour.

Some people love them, while others detest them, but tamarillo can be used in a wide range of different meal options. They are most commonly eaten raw - cut in half and eaten with a teaspoon, much like a kiwifruit. Cooked tamarillo are also delicious on toast, made into fruit pies, chutneys, sauces, used on cheesecakes, stewed with apple, added to salad greens and I'm sure there are other uses, too.

Site selection is important when planting a tamarillo tree. The best growing situation will be sunny, well-drained, as frost free as possible and sheltered from the wind. They are shallow-rooted and benefit from being staked. They are susceptible to mildew and whitefly which can be controlled by Yates Fungus Fighter and Yates Mavrik. This insect spray will also protect against infection from the tomato/potato psylid.

It is beneficial to water well during the dry summer months where the new growth formed is the basis for the winter harvest. Feed tamarillo trees in spring before pruning, a second feed a month after pruning and a third feed in February to aid fruit development. A good fertiliser to use is Tui Citrus Food or Novatec.

The two biggest enemies to watch out for when growing tamarillo are frost and wind. Although not quite as hardy as citrus, they can generally be grown in areas where citrus is grown. In Whanganui they grow readily in the many frost-free pockets and, with winter frost protection, where frost is heavier.

Where there is frost, tamarillo will be naturally pruned. Where no frost occurs, pruning should be done in spring. Fruit is formed on new spring growth so a hard prune will help maintain the shape of the plant as well as maximise the fruiting potential for the following year. On plants that have sustained some frost damage, remove any dead, damaged or old wood during spring after danger of further frosts has passed.

Tamarillos rate well as a source of dietary antioxidants compared to other common fruits and vegetables. They do not contain as much vitamin C as berry fruit or citrus but rate much higher than more commonly-eaten fruit, such as apples and bananas.

Below is a comparison of the vitamin C content (mg/100gm fresh weight) of some common fruit and tamarillos. Data from New Zealand Food Composition data base 2003:

Apple 8, apricot 7, banana 10, blackcurrant 160, blueberry 10, cherry 20, grape 4, kiwifruit 93, orange 50, pear 3, pineapple 25, plum 3, raspberry 14, strawberry 46, tamarillo - red 34.3, tamarillo – gold 24.7, watermelon 5.

Tamarillos also rank highly as a source of antioxidants compared with other foods. They rank significantly higher than apples, apricots, grapes, oranges and pears, but lower than blackcurrants, blueberries and strawberries.

Another subtropical favourite is passionfruit. They like a similar growing situation to tamarillos but are a climbing plant. The ideal site for them is a north-facing wall with some sort of climbing frame for the tendrils to attach themselves to. Passionfruit are heavy feeders and benefit from regular applications of citrus fertiliser. If the soil is poor, organic-based Ican Vegetable Food will help to improve soil structure as well as feeding the plant. They are not wind-hardy so need protection from cold winds and do not grow well in salty, seaside locations.

While they are relatively frost-tender, they will grow back from the base if burnt lightly by frost. It is important that vines are well watered during summer, particularly while the plants are young, and also in late summer when fruits are maturing. However, be aware that any water logging will rot these plants. If you do have a heavy soil, plant them in a mound to make sure there is good drainage.

If you would like to add some tropical flavour to your garden and plate, have a go at growing one of these plants.

Have a good week.

* Gareth Carter is general manager of Springvale Garden Centre