Acacia trees are large natives of Australia and Africa as well as other tropical to sub-tropical regions. Their propagation is through either seed or cuttings, with seed being the easiest method. However, these important members of arid communities require a few tricks to get seed to germinate. In the wild, fire promotes seed germination, but the home gardener can use other methods to crack the hard shells. Growing acacia from seed, once pre-treated, is then a simple and pleasurable process.
Growing Acacia from Seed
Acacia seed propagation is the preferred method for professionals and novices. Experts on how to plant acacia seeds recommend as fresh a supply as possible for the best chances of success. The shell coating is very dense and will take a long time to germinate without some attempt to break through this tough exterior.
Once the shell has undergone treatments, the germination success and speed is greatly increased. Sowing acacia seeds without such processes may still result in seedlings but is time consuming. Besides, the steps are easy and produce quicker plants.
- First, check that the seed is viable by placing it in water. Any floating seeds will not produce seedlings and should be removed.
- Next, scarify the seeds. This will crack them, something that fire will do in the wild. Use sandpaper, nail clippers or a gentle knock with a hammer, being careful not to smash the interior.
- The next trick is to place healthy seeds in a bath of boiling water overnight. This helps soften the tough exterior and enhance germination.
Once these steps have been taken, place each seed on moistened cotton pads in plastic bags. Put the bags in a darkened, warm location and check daily for signs of sprouting, generally in two weeks.
When you see seeds begin to germinate, make up a batch of potting medium. You may choose to use purchased seed starter mixture or make your own. A blend of sifted compost with fine river sand is one mixture recommended. You can also simply use straight compost. Good results have been shown with 1 part each compost, sawdust, shredded pine bark, and soil.
It is important the medium drains freely when sowing acacia seeds. Pre-moisten the selected medium. Use 2-inch (5 cm.) containers with several drainage holes and plant sprouted seeds at the same depth as the size of the seeds, gently pressing the soil over the sprouts.
Care of Acacia Seedlings
Planted seeds should be placed in semi-shade in a very warm location at least 75 degrees Fahrenheit (24 C.). They need 70 percent shading but can receive sun in the morning or late afternoon.
Keep the containers moderately moist. Acacia seedlings do not need fertilizer if the potting medium is sufficiently nutrient dense. If in a low nutrient preparation, feed them once they have several true leaves, with diluted fish fertilizer or compost tea.
Once they have a thick root mass, acacia are nitrogen fixers and will acquire sufficient nitrogen themselves. Plant seedlings outdoors in holes dug twice the depth and width as the original container.