Gareth Carter: Subtropical plants yield good crops in Whanganui

Whanganui's climate means subtropical fruit plants, such as bananas, can be grown successful in the home garden. Photo / Supplied

With regular rainfall, it is a good time to be making new plantings of trees, shrubs, roses and anything growing.

I myself have been busy planting many trees in the past few weeks; the constant rainfall and gradually warming temperatures of the season are helping with root establishment and growth. If you are thinking about planting a hedge – plant it now; if you are thinking about growing your own fruit – plant your fruit trees now. Want to sow a new lawn – plant it now.

While the spring weather has not been so nice to be out and about in, it is perfect to take advantage of good growing weather and make new plantings.

Despite the long grey and wet winter, overall it has not been cold. Our recognised temperate climate here in Whanganui continues to get milder, which means we can successfully grow an increasing number of subtropical fruit plants.

There is the edible banana "Misi Luki" and the previously unavailable cherimoya and casimiroa. There is unprecedented demand from home gardeners for avocado trees. Other favourite subtropical fruits, such as passionfruit and tamarillo, can also be planted in frost-protected positions in the garden.

Tamarillos, or tree tomatoes as they are also known, have long been a favourite of mine. They are one of those fruits that are always expensive when purchased from the supermarket and are always available for only a limited time each year. The fruiting time for tamarillo is during the winter months from May to July. This timing makes them a great fruit to grow because this can be a time of year when fruit and vegetables can be more expensive to purchase.

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

Tamarillo plants are fast-growing small trees that will fruit in their second year. They will reach full production capacity around four years from planting. They are relatively short-lived with an average tree fruiting for around 7-12 years before giving up.

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, which is best chopped to encourage a lower-branching canopy, whereas 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 leaves that are soft and hairy. Its size is about 3m x 2m.

When looking to plant a tamarillo tree, there are four varieties grown by Incredible Edibles that perform particularly well and have good-sized fruit.

Tamarillo Bold Gold: Clusters of pink fragrant flowers appear in spring within 18 months from planting. Followed by large golden fruit that is sweet and less acidic than the red varieties.

Tamarillo Teds Red: Clusters of pink fragrant flowers appear in spring within 18 months from planting. Followed by large almost round, bright-red fruit.

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

Tamarillo Lairds Large: This is a new variety on the market for 2020. It is described as a heavy-yielding variety producing large red tangy fruit.

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

When planting a tamarillo tree, site selection is important. The most successful 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. Tamarillo can be susceptible to mildew and whitefly, which can be controlled by Yates Fungus Fighter and Yates Mavrik. The Mavrik insect spray will also protect against infection from the tomato/potato psyllid.

It is beneficial to water well during the dry summer months when 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. Good fertilisers to use are Tui Citrus Food or Novatec.

The two biggest enemies to watch out for when growing tamarillos 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 undertaken 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, any dead, damaged or old wood should be pruned during spring after the danger of further frosts has passed.

Another subtropical favourite is passionfruit. They like a similar growing situation to tamarillos but are a climbing plant. The most ideal site is a north-facing wall with some sort of climbing frame provided for the tendrils to attach themselves to.

Passionfruit are heavy feeders and benefit from regular applications of citrus fertiliser and, if the soil is poor, organic-based Ican Vegetable Food will help to improve soil structure as well as feed the plant. They are not wind-hardy so need protection from cold winds and do not grow well in salty maritime locations.

While they are relatively frost-tender, they will grow back from the base if they have been burned 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. Be aware, though, that any water logging will rot these plants. If you do have a heavy soil, plant in a mound to make sure there is good drainage.

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

For more gardening information visit www.springvalegardencentre.co.nz

• Gareth Carter is general manager of Springvale Garden Centre.