It is also a good time to plant other fruit trees, including apples, apricots, nectarines, plums, pears, peaches, plumcot, peacharine, peach cot. There are also nut trees, too; almonds, hazelnuts, macadamias and walnuts can all be planted now.
Citrus performs well in Whanganui. Varieties of citrus include the well-known lemon, mandarin, orange, tangelo, grapefruit, lime, lemonade, and finger lime, and some lesser-known fruits like limequat and tangor (a cross between a mandarin and an orange).
These popular trees are both productive and ornamental in value. They can grow well in the garden or as container specimens with sweet smelling white flowers during spring and summer, and the fruits have a decorative effect during the autumn and winter months.
Whanganui has a climate which generally grows good citrus.
Most citrus trees are subtropical or tropical and will tolerate temperatures to around -2 C, and they are fairly slow growing, with a mature specimen years to reach four to five metres.
Where the location is sheltered from wind and warmer, the trees will grow and mature faster.
Citrus trees will generally try to produce fruit from the first year, but at this stage the tree's ability to bring fruit to maturity is often questionable, or it is at the cost of tree growth.
A good practice is to remove flowers and fruit for 2-3 years to allow a strong branch framework to establish itself. In subsequent years, if the tree is still producing larger crops than it can sustain, the removal of approximately 1/3 of the crop will ensure the tree does not get into a pattern of biennial bearing.
This is where the tree switches between a year of heavy fruit production and a year of minimal cropping.
To be grown successfully, most citrus trees are grafted onto a rootstock. The main rootstock used in New Zealand is trifoliata - it is vigorous, usually allowing the tree to grow to four or five metres over 15-20 years. It is also tolerant of heavy and wetter soils and creates increased frost hardiness. By trimming or growing it in a pot, a citrus plant can be kept at 1.5-2.5m.
Meyer lemons and Tahitian limes can be successfully grown on their own roots. These are particularly suited to pots and small gardens, as the plant vigour is less than that of a grafted tree of the same type, with trees reaching 1.5m if left untrimmed.
They still fruit prolifically from a young age; the plants just don't grow as big.
Citrus are gross feeders and thrive in good soil with regular feeding of a specialised 'citrus fertiliser'.
Plants which are showing yellowing of the foliage should in addition be given a top-up of magnesium.
Yates' liquid magnesium chelate is highly recommended. It is a product that makes nutrients readily available to the plant.
Where soils are lighter and sandy, particularly in parts of Springvale, Gonville and Castlecliff, an extra dose of Epsom Salts is recommended on a more frequent basis.
In lighter soils, particularly, an application of mulch around the base of the tree at the start of each summer will also be of benefit in conserving soil moisture & helping retain nutrients.
Pruning is only required for shaping, and plants are better left untrimmed from a fruit yield perspective.
Avoid any pruning between the early-spring-to-midsummer period to reduce the risk of attack from Borer beetles. If you do prune, be sure to seal cuts with pruning paste. The tell-tale sign of a Borer attack is sawdust piles on and around the plant from holes in the stems/trunk where the beetles are active.
This can be controlled via putting No Borer Spray Injector into the holes. They can be difficult to control, so prevention is better than trying to fix the problem later should it arise.
Any shoots from the rootstock should be removed as this will reduce vigour from the tree and subsequent fruiting potential.
A long hot summer when trees are well watered will result in better fruit production, followed by the cooler months, which promote the change of the fruit's skin colour from green to yellow. When the summer is cooler, the crop yield, size or quality tends to suffer.
When growing citrus in pots and containers, it is important to use a 'premium' potting mix, such as Tui Pot Power or Ican Premium Potting Mix, and to fertilise monthly or bimonthly using a specialist citrus fertiliser that is suitable for pots and containers, such as Osmocote for citrus or Yates Thrive Citrus & Fruit Granular Plant Food.
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 run-off and dry spots in potting mix and soils. It makes watering, rainfall and fertilisers more effective. It can also be used in the garden, even in sandy, clay or compacted soils.
The most common problem with citrus is usually sooty mould, a black sticky substance on the leaves and stems.
This is a secondary problem caused by the presence of, particularly, scale and aphids, which secrete a sugary substance while sucking the goodness from the tree, upon which the mould grows.
The sugary substance is also attractive to ants. The good news is this is easily controlled with a spray of a suitable insecticide such as Growsafe Enspray 99. This is an organically certified spraying oil. If you are unsure, then take some sample leaves into a garden centre for advice.
• Gareth Carter is general manager of Springvale Garden Centre.