The weeds included bamboo, barberry, blackberry, convolvulus, gorse, honeysuckle, periwinkle, wandering willy and wattle.
Some of the work done to make this area a butterfly-friendly habitat have included planting nectar and host plants for butterflies and moths.
Nectar plants include mānuka, kānuka, ti kouka, houhere, koromiko and hebes, while examples of the host plants are ongaonga (nettle), ti kouka, kowhai and mahoe.
Dave says it was a great honour and very satisfying that so many people went along last Friday to acknowledge the certification and the work that has been done.
He says he started restoration work on the bank because he had thought it might pose a risk to his property, and so started planting to try and minimise the risk.
He then came across the Moths and Butterflies of New Zealand Trust and decided he would also work towards making the area a butterfly-friendly habitat.
Dave says creating habitats like this for our native butterflies and moths is essential because they need plants in marginal areas as well as forests and gardens.
It is also important because native plants and insects are at risk, he says.
He says it always special to see beautiful red admiral butterflies and native birds such as fantails visiting the area, which he does usually see in the summer months.
"It's always a joy".
One of the main challenges Dave and his group of volunteers have encountered is navigating the steepness of the ground.
"We've got a few plans for the future. We want to develop it and encourage people to come and enjoy it.
"We also want to set up water retention that will give it resilience for long hot summer days. That's the hardest part of the year for us, so any little thing that could help this will benefit the plants."
Moths and Butterflies of New Zealand Trust secretary Jacqui Knight says it is wonderful to see the improvements that Dave and his group have made to this area.
"I cannot imagine what it looked like when they began nine years ago.
"It's an excellent example of habitat for our native butterflies and moths, and will be a great sight in the summer."