Autumn is the time to spray and fertilise citrus, such as this tree with a magnesium deficiency.
We are now firmly in the autumnal season, which means it is time to get into the garden and tidy up vegetable and flower gardens.
This is the time to make new plantings of trees, shrubs, fruits and any other plants that are not frost-tender. Planting in the autumn gives three seasons (autumn, winter and spring) for plants to get their roots established before the pressures of potential drought arrive next summer.
A plant I associate with autumn is the Chilean guava. The fruit of the Chilean guava are just starting to get towards harvest size and give off their delicious perfume.
Chilean guava is the common name for the bush, given the plant originates from Chile where its fruits are grown commercially, exported to Japan and sold locally. The other common name, NZ cranberry, is often a source of confusion because other than the look of the fruit, the plant growth and fruit taste are nothing similar to the “real” cranberry.
The Chilean guava produces attractive white flowers during spring and forms round, red berries (about 0.5-1.5cm across) during summer. Towards late February and during March these berries reach maturity. It is the ripening berries that produce the delicious smell. They are delicious to eat fresh as well as being suitable for making juices, jams and other preserves.
The plants yield quite well, with a three-year-old plant producing about 1kg of fruit, which will then increase by about 1kg a year.
The plants have a number of landscaping uses. If left unchecked they will grow to 1.5m high x 1m wide. They are best trimmed each year after fruiting to maintain some form, otherwise they can become a rather straggly and leggy bush.
They are great grown in a courtyard where the scent, when fruiting, coincides with barbecue season. The plants can be kept trimmed to size as the available space allows, by pruning after fruiting each year. They are suitable for containers and patios, where their drought-hardy tendencies can be useful, though lack of water can affect fruit quality.
The Chilean guava is regularly grown as a topiary. Its dense forming habit and small leaves make it an ideal candidate for topiary, which offers not just good form but the added value of scent and fruit.
They also make a marvellous fruiting hedge. Their leaves resemble those of buxus, though slightly more rounded, and their dense growing habit right from the base of the plant makes the Chilean guava a great hedge to consider. The growth habit is much faster than buxus, allowing establishment of a 30cm-high hedge in about two years rather than three to four. The tradeoff of a faster-growing hedge is that it will need trimming two or three times a year to maintain a tidy look.
Culturally they are an easy-care plant. The main insect offender to be aware of is thrips. These will often attack plants that become stressed from drought but are easily controlled with an insecticide such as Yates Mavrik if they become a problem. The plants are hardy to around -6C and are happy growing in full sun or part shade. They tolerate salty air but perform far better if they are out of the prevailing wind in a slightly more sheltered situation. They grow best in fertile well-drained soil; however, being very versatile they will also grow well in clay and even in sandy soils.
After a hot summer, there has been an explosion in insect numbers, including whiteflies, aphids, mites, scale, caterpillars and thrips on many plants. Rain throughout summer and now heavy dews have created more humidity, showing up many cases of blight, mildew and other fungus infections.
Maintain vigilant monitoring on crops for whitefly and caterpillar damage on tomatoes, cucurbits and newly-planted brassicas – it is wise to spray at the first sign to keep the population down for as long as possible. The population can build rapidly and, once in large numbers, control is significantly more difficult. Yates Mavrik is a good control – concentrate on the new growth where the pest is worst. If whiteflies have populated out of control, spraying every day for three to five consecutive days will break the lifecycle. Spraying with Grosafe Freeflo Copper mixed with Enspray 99 is recommended to control powdery and downy mildew on cucurbits and protect tomatoes from blight.
Another prevalent pest at this time of year is passion vine hopper, which attacks a wide range of plants. Insect sprays Mavrik and Pyrethrum will control this.
It has been a good season for growth and fruit development on citrus but be wary: I have recently seen a lot of citrus covered in sooty mould and closer inspection shows the cause – a heavy infestation of scale on the undersides of leaves. Now is the time to apply a spray of Yates Mavrik combined with 10ml per litre of Grosafe Enspray 99, which will kill the invaders and protect the new-season growth, ensuring good fruit production. A follow-up spray later in March or early April would be advisable.
Now is also a good time to fertilise citrus and ensure they are watered deeply. The plants will have fruit formed on them now and if they become stressed due to drought, the fruit may drop or quality can deteriorate. If your citrus trees are growing in pots or containers, ensure you use a specialist citrus fertiliser such as Ican Fruit Food for Pots or Tui Enrich Fruit & Citrus.
If leaves show signs of yellowing, a liquid fertiliser feed of Yates Liquid Manganese Chelates and/or Yates Liquid Trace Element Chelates is highly recommended and will give quick results to green them up.
Remember, a well-fed, well-watered, healthy tree will be far less prone and more resilient to insect and disease attacks.
The addition of Saturaid re-wetting granules to citrus growing in containers is highly recommended. This product should be applied annually. It channels water to the root zone, where it is needed most. It promotes even water distribution so there is less water runoff and dry spots in potting mix and soils. It makes watering, rainfall and fertiliser more effective. It can also be used in the garden, even in sandy, clay or compacted soils.
Gareth Carter is general manager of Springvale Garden Centre.
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