Acacia pulchella are highly attractive, fine-leaved small trees which rise to top form in containers on the patio or in a conservatory.
The acacia (Acacia) genus belongs to the legume (Fabaceae) family, where it is assigned to the sub-family Mimosoideae. The native Australian plant genus includes almost 1,000 species. Some of the non-winter hardy species are popular as houseplants. Caution: Acacia are often mistaken for robinia (Robinia pseudoacacia). This is also why robinia are also known as “false acacia". However, the two plant genera are not closely related. Acacia pulchella are also often called “Mimosa" although they also have little in common with real mimosa (Mimosa pudica).
Appearance and Growth
Acacia usually grow as evergreen shrubs, rarely as trees. Although they can grow between 16 and 49 feet tall. However, in a container, they generally only grow to around 6.6 feet. The branches of some species are thorny, the foliage is generally pinnate. The tannin-rich acacia bark is brown and cracked. Many species have honey to citrus-yellow colored ear-shaped or clustered inflorescences which have an enticing fragrance. They attract bees to collect nectar in their droves. The inflorescence appears from mid-winter to early spring.
Location and Substrate
As acacia like extremely light, sunny, warm spots, the container plants are best placed outside on the patio in the summer – if possible in full sunlight. If you have a suitable spot in the garden, the acacia can also be planted in a flower bed in its container. In its native Australia, acacia grow in steppe landscapes and sandy soils. Therefore, acacia should be planted in fresh, moist container bedding soil which is loosened with expanding clay, gravel, perlite or sand so that the substrate is loose and permeable.
As acacia form a wide crown, you should choose the largest possible container for planting. Ensure sufficient drainage in the pot soil and do not place acacia on plant pot saucers! Before planting, place the acacia root ball in a bucket full of water until all the air bubbles have escaped. Fill the pot with a drainage layer, cover this with plant fleece and fill this with container plant soil. Place the wet root ball into this, press in firmly and fill with soil to just below the edge of the pot. Acacia should also be well watered again after planting.
Acacia do not have very demanding care requirements. The plants cover their own nitrogen requirements through nodule bacteria in the root area. Nonetheless, it makes sense to give the densely foliated, rich-flowering small tree some liquid fertilizer diluted in its water every 14 days. Although acacia tolerate dryness for a long period, their dense foliage makes them very thirsty and they should therefore always be extensively watered with non-calciferous rain water. Cut back after flowering to keep the shape of the fast-growing crown and prevent it becoming bare. Caution: Do not prune the acacia in the fall, as otherwise it will miss a flowering period.
The non-winter hardy acacia are best overwintered in a cool and light conservatory with temperatures no lower than 41 to 50 degrees Fahrenheit. Here, they should also be regularly watered, albeit with less water, as the plant is in a resting phase. Stop fertilizing during this time. Caution: If the acacia is overwintered somewhere too dark it will drop its leaves. Acclimatize the plant when clearing in the spring and bring it slowly into the sunlight, otherwise it will quickly get sunburned.
Important Species and Varieties
Golden wattle (Acacia pycnantha) – not to be confused with Robinia pseudoacacia ‘Frisia’ - grows as a small tree in containers to about 6.6 feet tall and its luxuriant flowers live up to its name. It is the national plant of Australia. The ever-blooming mimosa (Acacia retinodes) is a large shrub which can grow up to 16 feet tall. Acacia retinodes flowers all year round with golden-yellow panicles in conservatories. Lots of water and sunlight make the dense, bushy kangaroo acacia (Acacia armata) flower outside in the garden in the early months of the year. The angular, thorny twigs handle regular pruning extremely well. Sunshine yellow cascades of fluffy flower pompoms decorate the meadow-like twigs of the golden wreath wattle (Acacia saligna) every year in the spring at a length of up to 20 inches. The rich-flowering silver wattle (Acacia dealbata) or false acacia is perfect for light, unheated conservatories. Its fine, pinnate foliate has a silvery shimmer. Its yellow flowers already herald the spring at the start of March.
Most acacia can be propagated through cuttings. For this, cut an approx. 5.9 inch long head cutting from the mother plant, remove the lower leaves, dip the cut end into rooting powder and insert the twig into a bowl with potting soil. The wood should be inserted about two thirds deep in the soil for good rooting. Cover the cuttings with a plastic hood or shrink wrap. When the first new leaves begin to emerge, the cuttings can be transferred to pots.
Diseases and Pests
When acacias shed their foliage, they are too dry, too wet and/or too dark. Yellow leaf coloration indicates too much lime in the water. It should be checked occasionally in its winter residence for mealy and scaly bug infestations.