Banana Musa spp
New Zealanders spend significantly more on bananas than any other fruit. On average, each family consumes 18kg of imported bananas every year. These are the heat-loving Cavendish variety from Ecuador and the Philippines.
It takes a little longer, but in the warm zones of New Zealand the hardier lady finger bananas will produce even tastier fruit.
Bananas are officially a herb, with underground rhizomes sending up ‘stems’ of tightly packed leaves.
Bananas need heat – they prefer temperatures around 27oC and will stop growing below 14oC. Lower temperatures will affect the fruit and frost will kill the plant above ground, but the underground rhizomes can survive and reshoot.
Wind will shred their leaves so plant in groups in a sheltered spot to recreate a humid jungle environment with regular water but free drainage. Tucked under the eaves on the sunny-side of the house is ideal.
Bananas are hungry plants, requiring lots of nutrients which they don’t like sharing with other trees. They want crumbly, friable soils and like all demanding, herbaceous plants, they do best if rotated to fresh ground every five to seven years.
Bananas are sterile hybrids - no pollination is needed.
Choosing the right variety for you
As New Zealand is on the limit of banana’s climatic range, the cold tolerance of varieties is the main consideration.
The Cavendish-type varieties require our very hottest temperatures and are more productive in a glasshouse. Dwarfing, and even a one-metre-high super-dwarf varieties are available.
The taller lady finger varieties (of which there are several) are the most commonly productive in New Zealand. They grow 3-5m high and have great flavour. Misi Luki from Samoa has been the choice for small commercial production in Northland. In the way-too-cold-for bananas-Waikato I have found my Ti Eke the most vegetative and
Australian Ladyfinger the first to flower.
However, breeding work in Honduras has recently produced Goldfinger for their high-altitudes which are more similar to our climate. Goldfinger is the first of a series (officially known as FHIA) – watch out for FHIA 2 (Mona Lisa) and others as they arrive in NZ.
There is also a range of inedible or ornamental bananas which are more cold-tolerant again. The Japanese fibre banana ‘Basjoo’ will even grow in Christshurch.
Banana plants are propagated by transplanting parts of the underground rhizome (known as the corm). This will send up numerous shoots (pups) which can be cut off from the parent plant with a sharp spade. For fast fruit production the pup should be over one-metre high with numerous roots, but even a piece of the corm with an eye will grow.
Plant in late spring when the soils are warming up – mid-late November.
Chop the top off the corm (the green leaves) to prevent evaporation during the transplant – it will regrow.
Plant two to five metres apart.
I do know some people who are planting bananas in large planter bags, bringing them inside in winter. This is only recent and they have yet to successfully produce fruit.
Bananas are demanding plants – starvation is the main reason for not fruiting. Feed with masses of animal manure and blood and bone every year as part of rich, composty mulch to maintain high nutrients. Wood ash mixed into the compost provides the potash bananas need to fruit well.
Mulch well to retain moisture levels through the summer months and keep warm in winter. After harvesting, chop the fruiting stem into the mulch.
Bananas also like humidity and water – commercial growers will turn overhead sprinklers on two to three times a day in dry periods.
In summer, well fed and watered plants will produce a 2m leaf every week, and the more leaves per stem, the more bananas per bunch.
Advice is that it is imperative to manage the size of banana clumps to no more than two full sized stems and two young pups each year. Otherwise the vegetative growth competes for nutrients and drastically reduces fruit production.
However I have seen unmanaged large dense clumps producing well and since my growth is so slow and my clumps still relatively small, I have chosen to leave as much growth as possible.
Thanks to our strict biosecurity rules, there are no serious bananas diseases or pests in New Zealand though pukekos will topple a mature stem to eat the sweet core.
In suitable conditions, NZ bananas will fruit after 18-22 months (double the time it takes in the tropics). Bananas don’t have a fruiting season, they flower after a set number of leaves have grown, usually 42. This can happen at any time of year but as winter cold will stop growth, it is unlikely to be June/July.
As each purple flower petal curls back and drops off, a hand of bananas is revealed. Fruit size will improve if the flower head is removed once the female flowers (banana hands) are exposed. Left on, tiny male fingers will form and the stalk keeps growing.
A bunch will take several months to ripen and will get very heavy – prop with a long pole to prevent it snapping with the weight.
Low temperatures will turn the fruit skin grayish. Covering the bunch with a perforated plastic bag (perforated to prevent fungal disease) will increase the heat and yield and prevent bruising.
Once one or two fruit turn yellow, you can harvest the bunch to prevent bird or rat damage. Since the stem will be cut down anyway, high bunches can be cut anywhere along the stem. (Large bunches can be heavy and stem sap can stain clothes.)
Chop the stem into the mulch, blast the bunch well with water to dislodge bugs and leaves and hang in a warm spot indoors to ripen. They will ripen all at once so be prepared.