Propagating mangoes

Establishing a healthy, productive orchard requires planning and preparation. Once you have determined that the climate and soil is suitable and selected varieties, you must also decide on how to propagate the planting material.

The two basic propagation options for mangoes are by seed or grafting. The best propagation method will depend on the cultivars required and the growing conditions.

Mango seeds are either mono-embryonic (single embryo) or poly-embryonic (multiple embryos) depending on the variety. Only poly-embryonic seeds produce true-to-type (clones) of the parent.

Most cultivars of mango do not produce seedlings true-to-type. Therefore, grafting is often necessary to overcome this problem. Grafting also means that trees produce uniform yield, fruit size and quality.

Propagation by seed

Propagation by seed is only recommended for poly-embryonic mango varieties such as Kensington Pride. Poly-embryonic seeds produce a number of shoots, one of which originates from fertilisation. The fertilised seedling is often weak and stunted and should be discarded. The other seedlings are clones of the mother tree.

However, any seed can be used to grow seedlings for grafting. The seedling will become the rootstock. Collect seconds fruit and use to propagate rootstock.

Preparing seed for planting

Mango seeds lose viability very rapidly. It is essential to clean the seed as soon as possible after its removal from the fruit. It then needs to dry in the shade for a day or two.

The outer husk must be removed before planting. The easiest way to extract the embryo is to cut the husk at the stalk end of the fruit to create a small slit. Then pry open the husk with a seed opening tool. A tool can be made by welding the heads of two flat screw drivers to a pair of circlip pliers.

Opening mango seed husk to remove embryo
Opening mango seed husk to remove embryo

 

Opening mango seed husk to remove embryo.
Opening mango seed husk to remove embryo

You can tell if the seed is mono- or poly-embryonic by the number of segments.

Mono-embryonic seed has one section only while poly-embryonic varieties uuch as Kensington Pride divide into several sections
Mono-embryonic seed (left) and poly-embryonic seed

Use a seedling bed

If you are propagating large numbers of seeds consider using a seedling bed. This method saves space, potting medium and time.

Have a large tray filled with potting medium. Good potting medium contains slow release fertiliser, 50% coarse river sand, 25% vermiculite and 25% sphagnum peat moss, and as a minimum should meet the Australian Standard for a standard potting media. Premium media is also available. This is indicated by Standards Australia certification stamped on the bag.

Plant seeds next to each other, about a centimetre apart. The seeds are kidney-shaped. Plant the seed on its edge with the concave edge facing downwards.

Plant the seed concave side down
Plant the seed concave side down

Leave part of the top of the seed uncovered. If in a few days the seed is green it is healthy and should grow well. If the seed is brown or black it is probably rotting and can be removed and replaced with anothe seed.

Leave part of the top of the seed uncovered
Leave part of the top of the seed uncovered

As the seeds germinate they can be carefully removed from the seedling bed and planted into individual pots.

Germination takes between 10 and 14 days. Within eight months they will have reached a stem diameter of 8-10mm and be 10-15cm high.

Propagation by grafting

Grafting is the process by which part of the parent tree to be reproduced (scion) is joined with a rooted plant (rootstock).

Selection of rootstock

It is important to have rootstocks of similar characteristics to ensure a uniform plantation.

Grafting is best performed when weather conditions are milder, for example autumn or spring. If the seedlings are not yet big enough, delay grafting by two to six months.

Rootstock ready for grafting
Rootstock ready for grafting

Preparation of scion material

The best scion material is obtained from the tips of mature shoots with prominent buds (tip wood) immediately before flushing.

Tip wood can be prepared on the parent tree 7-10 days before they are cut for grafting. Prepare the tip wood by cutting off the leaves but leaving the petioles (leaf stems) attached. The petioles will fall off easily when the scion is ready.

Pre-prepared scion on the parent tree
Pre-prepared scion on the parent tree

The scion is cut from the mother tree when required and needs to be 6-8cm long and as close as possible in diameter to that of the rootstock.

Scions can be stored for up to seven days wrapped in a moist towelette or newspaper in a zip lock plastic bag in a cool, dark place. If propagating large numbers, drop batches of scion wood into a bucket of water to stop them drying out.

Alternatively, the budwood can be selected on the day and prepared by remove leaves, but leaving the petioles. The scion is ready for immediate use.

Preparing a scion in the field
Preparing a scion in the field

Wedge graft

The wedge graft is the easiest graft to perform with a 90-100% success rate.

The keys to success are:

  • Choose vigorous rootstock and scion material.
  • Use a razor sharp knife or scalpel.

Materials required include grafting/budding tape (12mm wide) and zip lock plastic bags.

Grafting tools and equipment
Grafting tools and equipment

Select a scion that is the same width or slightly narrower than the width of the rootstock.

Choosing a scion that is the same size or slightly smaller than the rootstock
Choosing a scion that is the same size or slightly smaller than the rootstock

The scion needs to be semi-hard, so that when slight pressure is applied it bends slightly. If the tip is too soft it will not cut easily and will dry out quickly.

Cut the end of the scion into a wedge. Use as few cuts as possible, only one or two on each side of the scion.

Cutting the scion into a wedge
Cutting the scion into a wedge

Cut off the top off the rootstock and then cut a 2cm slit down the middle.

Cut the top off the rootstock
Cut the top off the rootstock

Cut a 2 centimetre slit into the middle of the rootstock
Cut a 2 centimetre slit into the middle of the rootstock

Push the scion wedge into the slit on top of the rootstock. Try and line up the cambium on at least one side. The join on at least one side should feel smooth where the edge of the scion and rootstock meet. It does not matter if there is a slight indentation on the opposite side.

The cambium layer can be seen as a dark green ring just inside the bark. The ring can be seen when looking at the cut end of the scion and the rootstock once the top has been removed ready for grafting.

The scion should be flush with at least one side of the rootstock
The scion should be flush with at least one side of the rootstock

Wrap graft with grafting tape
Wrap graft with grafting tape

Place a zip lock bag over the graft with two leaves inside the bag and seal on each side.

Place a zip lock bag over the graft with two leaves inside the bag and seal on either side
Place a ziplock bag over the graft with two leaves inside the bag

About two weeks after grafting the terminal bud will start swelling. As leaves appear the bag can be removed.

Scion shooting 21 days after grafting
Scion is shooting 21 days after grafting

The grafting tape can be removed after 8-10 weeks once the graft union has healed, or longer if necessary.

Graft tape removed 90 days after grafting
Graft tape removed 90 days after grafting

Graft tape should be removed immediately after any restriction of plant stem is seen. Suckers from the rootstock, below the graft, must be removed as they appear.

Side graft

This graft is used when the rootstock is much larger than the scion material. This is an effective graft, but requires more experience.

First, cut a long sloping cut (25-30mm) on the side of the rootstock at about 10-20cm above soil level. Do not sever the rootstock. The top portion is temporarily retained.

Cut the scion into a wedge with one side slightly longer on one side. The length of the wedge needs to match the length of the cut in the rootstock.

Exert slight pressure on the rootstock above the incision. Insert the scion lining up the cambium layers. Cut off the top of the rootstock just above the union. Bind the graft with grafting tape. Cover the graft with a zip lock bag and seal on each side.

Care of grafts

Newly-grafted plants need 50% shade. Do not overwater, remember that the reduced leaf area means that the plants require less water.

Remove any shoots that may develop below the graft.

Depending on the growth and vigour of the plants, the trees should be able to be planted out six months after grafting.

Do not plant out if the trees are flushing. The new growth will get sunburnt and lead to poor establishment.

Reworking

Varieties of mature trees can be changed by “reworking”. The tree needs to be in good health for this process to be effective.

First, the old trunk is cut leaving one nurse branch. The nurse branch will provide some shade and help produce energy to grow new shoots. Paint the trunk with diluted white acrylic paint to protect it from sunburn.

Shoots will develop around the trunk. When these are 7-10mm long, three or four can be grafted as described previously. Cover the grafts with paper bags to protect them from sunburn.

The reworked tree should produce fruit within two years.

The only disadvantage of this technique is the possibility of weak unions. Some branches may break off when heavy production starts or during severe storms.

Page last updated: Thursday, 8 June 2017 - 11:52am

Author

Tara Slaven