Daleys Fruit Tree Blog
Description and Origin:
Avocados are large upright trees growing to about 9m, depending on the variety, although vigorous seedlings can reach twice this size if the conditions are right. The Wutrz is the smallest variety reaching only 4-6m, making it suitable for smaller home gardens.
Avocados are native to southern Mexico. There are three groups of avocado, Mexican, Guatemalan and West Indian. Most of our varieties are hybrids between the Mexican and the Guatemalan, these trees are a little more cold hardy that the more tropical West Indian varieties which are seldom seen in Australia.
Grouping and Pollination:
Avocados are split into two groups, A and B, for the purposes of cross pollination. If a variety from each group is planted together they will cross pollinate with each other and each tree will produce more fruit than if grown on its own. The fruits take different lengths of time to mature from flowering therefore the fruiting season will also be extended. If there is only room for one tree the A groups tend be more self fertile and will set better on their own than the B group.
Location and Planting:
Avocados require a full sun position with protection from strong and salt laden winds. The root system is spreading and competitive and they should not be planting too close to buildings or pathways. They do not like root disturbance so take care when planting to disturb the roots as little as possible, to remove young trees from their growing container, cut down the side of the bag and gently lift them out. Give the tree plenty of room to mature; the minimum spacing should be 6m or more between trees. Avocados are very fussy about drainage and will not accept anything less than perfect drainage. 24 hours in a waterlogged position will kill an avocado tree. Avocados thrive in rich, deep, sandy loam soils with a ph of 6-7. They will not survive in a position with poor drainage. If the planting site has heavy clay soils it will need to be mounded with a large pile of compost so that the tree is planted into the mound above ground level, the mound may need to be 1m tall and wide or more if possible. This is essential for good drainage and the survival of the tree. Water and Nutrients:
Trees grow and produce better fruits if they receive regular moisture. Over irrigation can induce rot which is the main reason that avocados fail. To test to see if irrigation is necessary dig a hole about 20cm deep and test the soil by squeezing it together, if it is moist and holds together do not irrigate, if it crumbles in the hand, it may be watered. Young trees are fairly nutrient hungry and like rich, organic soils. Regular applications of fertilizer with added nitrogen, about 4 times a year will be beneficial. Mature trees need only one application of fertilizer in the spring during fruit set with a reduced nitrogen ratio. Too much nitrogen results in excessive leaf growth at the expense of fruit production. Alkaline soils can result in iron chlorosis which appears as yellowing of the leaves, this can be corrected with applications of chelated iron. Protection and Pruning:
Young trees will need protection from both frost and very hot direct sunlight which can burn the stems and trunk of young plants. A small house constructed of 4 star pickets or tomato stakes wrapped with shade cloth or Hessian will do the trick. On cold frosty nights a hat can be placed over this structure to protect young trees. The Bacon has the greatest cold tolerance of the avocado varieties; this can endure temperatures down to -5 degrees. Once established most varieties can handle -2 degrees with little damage. Young avocados can be tip pruned to encourage a bushy habit. Mostly though, avocados do not need pruning. If the tender green branches are exposed to direct sunlight they can suffer from sunburn and dieback. Whitewash any exposed branches with diluted white paint to prevent this. Mulching:
Mulch avocado tree with a thick layer or organic mulch like Lucerne hay. This not only retains moisture levels in the soil, but it also suppresses weeds, protects the root system from extremes in temperature as well as adding essential nutrients to the soil. Make sure to keep the area around the stem of the plant free from mulch, it should never come into contact with the tree as this can cause the trunk to rot.
Knowing when to harvest the fruits can be tricky, mature fruits will show the following signs; the fruit stem will become more yellow, when the fruit is cut and the seed removed, the seed coat is dry and does not stick to the flesh, it is a dark brown colour, dark skinned varieties will show a change in colour from green to purple. Knowing which variety you are growing will tell you when to pick the fruit. If you are unsure pick only one fruit and leave it for 7-10 day to ripen, once it softens the flesh should be a rich green colour, soft and buttery. If the fruit turns black and wilts it is not ripe and needs to be left longer on the tree. Varieties are harvested as follows: Bacon- March – May, Fuerte- April – June, Hass- July – August, Pinkerton- June -August, Reed- August – December, Secondo- August – December, Sharwill- June – July, Sheppard- February – April, Wurtz- August – October.
A. CARE OF PLANTS BEFORE PLANTING
Place trees in a position that has direct sunlight for at least half the day and protection from strong winds. Water regularly and thoroughly.B. SITE PREPARATION
If possible, site preparation should begin 6 months prior to planting. The following points should be considered:
1. Fencing the Orchard. This is particularly important if your trees are subject to damage from stock or native wildlife particularly wallabies.
2. For poor soil (i.e. less than 1 metre of top soil and heavy clay soils) Deep Ripping is advised to improve drainage (rip to a depth of at least 45cm). The last Ripping should be down the slope, as deep as possible to help sub-soil drainage. Erosion control will prevent washing out of furrows.
Diversion Drains at top of orchard site are recommended.
3. If soil is too shallow, mounding of tree rows will improve drainage as well as increase depth of topsoil.
4. Green Manure Crops improve the organic matter content of soil and can be ploughed in approx 1 month prior to planting.
5. Wind break trees are very important and should be planted before fruit trees. Windbreaks should be planted along south, west and east sides of orchard, leaving the north side open. C. PLANTING THE TREES
Most trees can be planted out at most times of the year, provided the following points are followed:
1. If soil is not well drained it is advised to make a circular mound 1.5 metres across and 20-30cm high. This can be achieved by bringing outside loamy soil to the planting site or alternatively mound existing soil. Do Not plant trees in holes in heavy clay soils as the hole will act like a sump and hold excess water.
2. The trees should be watered thoroughly several hours before planting to moisten the root ball. Planting trees out with the root ball dry or partially dry will result in roots being damaged. The site should also be thoroughly watered the day before planting.
3. Make a hole in the soil or mound twice the width of the pot and the same depth as the pot. Remove the tree from the pot and lightly tease roots down side of the root ball and loosen any matted roots at base of root balls. Fill in soil around roots, making sure not to plant root ball any more than 2cm lower than it was in the container. Trees will suffer if planted too deep. Soil should be firmed down well after planting. At least 20 litres of water should be applied to each tree to settle in soil around roots. A saucer shaped depression 50cm in diameter will help hold water when watering in.
Applying a Slow Release Fertilizer at planting will help the young trees off to a good start. This can be applied by scratching into the surface around the young tree. One of the following or a mixture can be applied.
Blood Bone, Dynamic Lifter, Osmocote, Nutricote or Nitrophoska
If mixture is applied, reduce quantities of each proportionally. If soil is acid also apply dolomite or lime.
5. Staking - trees are better off not staked, but if needed, two tomato stakes on each side of tree (30cm from tree) will support tree by using old pantyhose or similar material.
6. Mulching the trees with old straw, hay etc, will stop soil from drying out, heating up, stops weeds from germinating and also adds valuable organic matter. Do Not apply mulch against trunk of tree as Collar Rots may occur. Trees that are susceptible to frost damage are better off without mulch during the winter months, the reason being that bare soil kept moist will absorb heat during the day and radiate this heat at night reducing severity of frost.
7. Grow Bags placed over young trees will give protection during the winter months and allow an early growth in spring. They also protect trees from wildlife.D. CARE OF TREES AFTER PLANTING
1. Plant tags and ties – It is important to remove any tags and ties. Even a thin string can ring bark and kill a tree as it grows. Ties can be left on to secure a tree to its stake in the early stages but the tension must be frequently monitored. Relocate labels to an adjacent stake.
2. Weed Control - Most important if trees are to grow quickly. Weeds shouldn’t be allowed to grow within one metre of the tree for the first year. After this keep area out to the drip line (i.e. width of foliage) free of weeds. Mulch will control most weeds.
3. Fertilising-Trees will respond to feeding. How often and how much fertiliser to apply will depend on soil type and the trees requirements (refer to Dept. of Ag 'Ag Facts' for specific requirements). If you do not want to use chemical fertilisers consider applying one or a combination of organic fertilizers (e.g. poultry manure, rock phosphate, blood and bone etc).
4. The use of Organic Mulch is very important for healthy trees. Any organic material can be used, e.g. Lawn clippings, weeds, straw etc. Hay, especially soybean stubble is excellent. As the mulches break down they will feed the tree with valuable nutrients.
5. Watering-Setting up a permanent under-tree sprinkler irrigation system is well worth considering. Frequency and amount of watering will depend on a number of factors, but a good watering once a week is a good guideline.
6. Remove any shoots coming from below graft on grafted trees while trees are young. The removal promotes growth of grafted variety only.
6. Pruning-Fruit trees need pruning to produce good crops of fruit as well as keep trees to a manageable size. Most deciduous fruit trees in particular need annual pruning. Pruning also invigorates the tree and encourages new fruiting wood for the following year