Site Preparation:
Site selection is of prime importance and soil should be deep and well drained. Apply base fertilisers (lime, gypsum, phosphate) according to a soil analysis. Depending on the site, pan breaking, drainage, and deep ripping (to a depth of 60 cm) may be required. As avocado trees are highly susceptible to both water logging and Phytophthora root rot disease, any practice that will improve the soils aerobic capacity and drainage rate could be the difference between success and failure.
Planting:
1. Avocado trees respond very well to heat, with warm soils promoting optimal root growth. For this reason, we recommend planting between mid-October and late-February. Planting outside these periods is possible, but extra care is needed to protect from frosts.
2. Young trees are fragile and should be transported in a covered, well ventilated vehicle. Always pick up trees by the bag and NEVER by the trunk.
3. Growers should plant the young trees as soon as possible after delivery. A long delay between nursery care and planting may cause unnecessary tree stress. If trees do need to be stored ensure they don’t dry out, by watering thoroughly once per week.
4. Drench the root ball (whilst in the bag) in a weak solution of a 40% Phosphorous Acid product, at a rate of 2 mls per litre. (Rate as per Ken Pegg) This means putting the entire bag into the solution so the growing media is covered. Within a few seconds the bag will be drenched (no more bubbles) which both hydrates the tree totally and gives the tree some early protection against Phytophthora.
5. Paint stems with watered down white acrylic paint to protect against sunburn. The solution needs to be thick enough to provide an effective sunblock and cover as much green stem as practical.
6. Dig a hole slightly deeper and wider than the bag. Put some soil back into the hole to ensure that when planted the top of the growing media is 25 mm above the surrounding ground level. Excess soil is then pulled to the level of the growing media, so the entire plant is slightly mounded.
7. To remove the plant from the bag, cut the base of the bag and remove the base. Care must be taken when cutting the polythene bag to minimise root damage. Then cut a slit half way up the bag. Place the tree in the hole, fold up the cut bag and cover the exposed root ball. Slit the remainder of the bag, remove, and cover the remaining roots with the top soil, gently pressing the soil into contact with the root ball from the sides towards the centre. Care must be taken at this stage as the roots of avocado trees are very brittle and break easily. NEVER TEASE OUT THE ROOTS! Do not tamp the soil down with your feet. Position the tree in such a way that most of the branches and leaves face the direction of the sun in order to protect the tree against sunburn.
8. It is very important to check the planting depth as planting too deep may result in collar rot and planting too shallow will expose the unplanted stem and prop roots to sunburn and other physical damage.
9. Soon after planting, the young trees should be supported with a strong wooden stake. Do not push the stake through the nursery growing media as this will damage the roots. Tie the tree firmly to the stake attaching above the side branches. Regularly check that the ties are still effective (every four to six weeks) and note that it may be necessary to loosen the ties to prevent them from strangling the tree.
10. Trees must be protected from wind. There are many techniques to achieve this including existing shelter belts, bana grass, long run artificial shelter and individual tree shelters. The better the shelter, the faster growing, and earlier producing, the trees will be.
11. Irrigate well the day after planting as this helps to bring the soil into close contact with the root ball.
Aftercare
1.Proper irrigation of young trees is very important! It is important to water your trees, then let them have a chance to dry out-the oxygen they get is just as important as the water they get! Lynwood uses a coarse, free draining growing which will dry out faster than the surrounding soils. This helps us grow great roots in the nursery, but in hot windy conditions the media will dry out within a week. If the media is allowed to dry out too much it becomes hydrophobic and can be difficult to re-hydrate. When a decision to water is made is it important to completely hydrate the growing media and surrounding area. Always be aware of where your roots are (have a dig from time to time); this is the crucial area. Tensiometres or other moisture probes are very useful for accurate irrigation scheduling.
BEWARE: more trees die because of too much water than too little-they can literally drown! When we say too much we mean too often! Do not be panicked into watering because the tree is wilting during the day-the tree is simply having difficulty drawing enough water to keep itself cool. Rather examine morning or evening for a better visual indicator.
2. Mulch trees well to increase the soil organic matter, improve the soil structure, reduce evaporation and fluctuations in root temperature. Keep the mulch away from the stems to avoid collar rot; however, mulch can be used to cover newly exposed roots. Remember to also apply mulch around tensiometres.
3. Alternate the following three sprays, doing one every two weeks:
- a) Trees should be protected against Phytophthora with foliar sprays. Use a 40% Phosphorous Acid product at 7.5 mils per litre.
- b) Foliar feed with a combination Nitrosol and Wuxal Ascofol at label rates.
- c) Fungi and frost protection using copper at label rates.
- These products can not be combined.
4. In addition, granular fertilisers and/or fertigation can be applied to the soil 40 cm around the stem, being careful to avoid contact with the stem. Apply as per consultant’s recommendations.
5. Weeding is important to prevent competition with the avocado tree roots. Hand weed an area 1 metre diameter around the trees, whilst trees are very young. Avocado feeder roots can be very close to the surface and even grow up into the mulch so don’t risk exposing the tree to herbicide.
6. Regularly inspect trees for pests. Remember Grass Grub and Fullers’ Rose Weevil can start feeding on plants the night of planting. Also pay attention to Leafroller Caterpillar, Thrip and Six Spotted Mites.
7. If planting in a cold region it is necessary to protect the young trees against frosts.
8. Remove all flowers for the first 18 months as these will compete for limited tree reserves. This will mean visiting the trees several times removing flowers as soon as possible as they extend. If trees are particularly strong (lots of vegetative growth is apparent) consider leaving the flowers and fruit on.
9. Remove any shoots that develop below the graft union as soon as they are seen to be pushing out