Dear Agony Aunt,
On my recent travels across our picturesque Hunter Valley, everywhere I look, I’ve noticed an evergreen plant. It dominates roadsides and creek-lines and ventures out into paddocks. I usually see it sprouting up underneath other trees. I’ve seen fruits on them a few months ago that looked like olives. Are these real olive trees? Can I eat the fruits?
from Hesitant in the Hunter
Dear Reader,
Don’t get the bottling jars out. Sounds like you’ve come across the well known African Olive or Olea europaea subsp. cuspidate.
This is another plant that unfortunately falls into the ‘Garden Escapees’ category, first being introduced to Australia in the 1800s as a hedging plant and as root stock for edible olives. All the way from north Africa and western Asia and now growing vigorously throughout NSW, African olive is readily dispersed by seeds, (mostly by birds or soil movement over short distances), while nursery trade has spread it further afield, making it one of the Priority weeds for the Hunter.
African Olive (Olea europaea subsp. cuspidate) is different from the European olive or Olea europaea subsp. europaea, which has the edible fruits (that we like to enjoy with cheese and biscuits!) that it is farmed and famous for.
To tell the difference between the two, Weeds Australia states:
‘African Olive normally has larger leaves; from 6–10 cm long, and wider leaves 1–2.5 cm wide, with the lower surface green or yellowish brown.
European Olive normally has smaller leaves; from 3–7 cm long, and thinner leaves 0.8–1 cm wide, with the lower surface whitish or silvery.’
The European olive has become a major environmental weed in parts of temperate to humid south-east of Australia, mainly South Australia and Victoria. The one you see in the Hunter is mostly African olive…
But there is another, local contender…
Just to confuse things, there is the native olive, Notelaea microcarpa, which is generally found in dry sclerophyll woodland.
So how can you tell the difference between the two? There are certain ‘telltale’ characteristics which our Upper Hunter Coordinator, Paul Melehan explains here.
Notelaea longifolia or Large Mock-Olive is another native, which is a very common shrub or small tree in eastern Australia.
Once suitably identified, there are various treatments you could try to reduce or eliminate African olive on your property, listed as Biosecurity Duty Regional Recommended Measure* (for Regional Priority – Containment).
{For more Biosecurity guidelines, see the 1-page document from Upper Hunter Weeds Authority (UHWA) General Biosecurity Duty Control Guideline here}.
Like most effective weed control, a combination of methods are most effective, as well as regular follow up after initial efforts, with the aim to control plants before they fruit.
Hand weeding African olive is an effective method of control, digging out the seedlings and removing all the roots. It is worth noting that African olive re sprouts from the base if it is cut down or burnt.
Chemical control methods can be varied, depending on the size and scale of the infestation.
Spraying: Seedlings or small plants can be sprayed, ensuring all foliage is covered.
Cut stump: For plants up to 10cm in diameter. Cut the stem to no longer than10cm above the ground. Apply herbicide in 15 seconds.
Stem injection: For plants with a stem greater than 10cm in diameter. Use a drill to make holes or axe to make cuts all the way around the trunk. Inject or apply herbicide within 15 seconds of cutting.
Basal barking: Spray or paint herbicide mixed with diesel all the way around the trunk or stem of the plant from ground level to a height of 30 cm. Wet thoroughly.
Herbicide options can be seen here.
African olive is a perennial plant with seeds germinating in Autumn, with the plant growing for several years before flowering. It flowers in summer, and the fruits ripen in winter. It produces dense shade that supresses native understory plants and can change plant diversity in bushland as it becomes a monoculture. Weeds Australia states that the plant may be effectively controlled by grazing, as stock find it palatable.
Please help spread the word about recognising and dealing with African Olive on your travels by sharing this post. Good luck with your treatment of this weed and be sure to enjoy some fruits of the Olea europaea subsp. europaea with biscuits and cheese at the end!
