20 Invasive Weeds Destroying NZ Forests You Need to Know These.

This week we're going to take a look at invasive weeds that have been introduced into New Zealand that are destroying our native forests. So beside me is a good example of that. This is a Bramble, part of the Rubus genus, and it is highly adapted to get in there and multiply and spread. Part of the reasons they can multiply is it's got nice tasty fruit, small seeds that birds will come along, eat, fly away, poop out into areas like central native forests. It's also got a good way of covering land. It scrambles and then gets quite dense which blocks out areas for native seedlings to germinate. And it also has a way to climb. It's got thorns on its stems and it can twist around and climb up to the higher canopies and also start to block out light from those trees and then end up killing those as well. So this plant is highly adapted to survive. It's looking for space for land to occupy. It's looking for light because light for all of these plants is the energy source so it's a prime commodity. And so this is just one of the invasive weeds. There's around about, identified around about 300 or so problematic weeds for New Zealand and we really need to sort of start thinking about how we're going to start controlling these plants because at the moment we're riding on the Titanic and the ship is sinking little bit by little bit. These plants are making their way into the New Zealand forests and that's something we don't really want because at the end of the day we want New Zealand forests to be able to survive. They've adapted for millions of years. We have a lot of endemic species that are relying on those sort of environmental conditions that they can still be able to thrive. Unfortunately these plants from other parts of the world are highly adapted and they're going to knock out our native forests if we're not careful. So we really need to take a look at these problems and these plants and see what we can do about it. These plants obviously would have been brought in by just people wanting some berries, people wanting to house plant and just chuck that out into the compost heap and then before you know it they spread and then they're moving across and encroaching into our desirable native forests. So that's what we're going to take a look at today, how we can sort of identify some of these problems, some of these weeds and see what we can do about it. In this part I wanted to compare the native plants to introduced plants. So this is a bar graph that I created from a paper that was published called Naturalized Plants Transform the Composition and Function of the New Zealand Flora. It's a very interesting paper put together by many scientists. We have got 2,299 native plant species approximately and out of those most of those are actually endemic to New Zealand. So 80% of those plants are endemic, that's the angiosperms, that's the flowering plants and 100% of the gemnosperms, that's the conifers, things like the podocarp. Now on the other side of that graph we can see the introduced plants. We have a huge 25,000 plants introduced. These are the ornamentals, the exotics. Many of them are very good. So we've got fruit trees, the citrus, all the fruit trees, all the landscaping plants, all the agricultural plants. Many of them have been an asset to New Zealand. Out of that 25,000 about 1,800 of them have naturalized, which means that they can grow out in the environment, set seed and be okay. Out of the 1,800, 314 have been described as environmental weeds, problematic weeds, potentially killing off New Zealand's native forests. So that's a huge problem. So if we look at where these weeds are distributed, you can see from this map of New Zealand that the naturalized plants and the environmental weeds are in the city areas. So mainly in Auckland, mainly in Canterbury Christchurch areas, but all of those major city areas, you'll find a huge amount of problems with weeds. Now this is simply because a lot of people will bring plants in for their gardens, for their landscape. They'll use them for hedging, for trellis, for pot plants. Now at some point you'll find that these will spread. So for example, ivy spread basically through its berries when you get a bird to transport the seed. But we've also got a lot of weeds on the roadside and in farmer's land and also private land. So you'll see farmer's land where it's been neglected. A lot of, again, a lot of plants allowed to proliferate. And of course we've got different weeds from the tropics, tropical north down to the cold alpine south. And so all different. So if we have a quick look at the different parts of the native forest, look at the very top, we've got the emergent layer. This is things like the potocarps and the totras, remus. Then below that we've got the canopy. These are things like the tawa and the tariri and those broadleaves. And then underneath that we've got the understory. So these are things like the nikah palms, the ponga and the kawakawa. Right at the bottom we've got those things that like the shade. So those ferns and also things like hebes and astelias. Now these weeds, these invasive weeds that come in, they will be affecting different parts of this structure. And quite often you're looking at the climbers who are able to grow up in the shade and get right to the canopy tops and collapse those canopies. Those are usually the worst invasive weeds. So now we'll have a look at the different weeds affecting different parts of the forest and we're going to start off at the canopy. One of the worst weeds that we have is one called old man's beard. It's the Clematis vertelba. It was introduced in late 1800s but escaped gardens very quickly. It's a very fast grower and it can grow quite quickly up to those canopies and start smothering them. Now it is very hardy so it can grow throughout New Zealand. It's from zones four to nine and also produces lots of viable seed which are spread by the wind. Now it shouldn't be confused with our native Clematis, Clematis verniculata, because that is our evergreen vine climber and that is a desirable plant. But the old man's beard is definitely one we need to get rid of. I used to have this next plant in my first garden and it was an absolute pain. It is the jasmine, the oriental jasmine. It's jasmine polyanthem. Now the big problem with it is that it has sort of these sort of suckering stems and root systems that go on and if you pull a little bit up that doesn't always get rid of it. You have to go down and sort of dig it all out. Now it has got very fragrant flowers which is why people like growing it, but it does sort of distribute itself pretty quickly and will climb up to the top canopies and destroy all those plants around it. This is another vine similar to the last one. It is the Japanese honeysuckle, Lonicera japonica, introduced as an ornamental climber. Again it's got nice fragrant flowers but it's very vigorous and what happens is it's spread also by the birds and it will have the sort of suckering system as the last one. So very very invasive and it is hardy in four to nine so will grow throughout a lot of New Zealand. This next climber is a major invasive weed in New Zealand. It is a one that will cover and smother the ground but it also has the ability to climb up trees. One of the big problems with it is it produces berries that are very desirable by birds and they will eat it and poop it out somewhere, usually at another tree and then that will grow up that tree to smother and kill it. So it's a very very difficult one to get rid of because it has also little roots on the stems of it and if you just pull out one part that doesn't necessarily get rid of it. You have to pull out the whole lot. This next climber is definitely one of the worst climbers especially in those warm zones of 9 to 11. It is the banana passion fruit, Passiflora taramiana. Now it has edible fruits and pretty flowers but the problem with it is those fruits also have seed in which can be spread by birds and it is a very fast growing climber and will smother the tops of those canopies very quickly. This next climber is the bindweed. It's the convolvulus species. There's a couple of different types but they spread very quickly. Introduced around the 19th century and probably likely imported with agricultural seed. So it spreads very quickly especially on open disturbed ground roadsides and in gardens and it is a bit of a problem because it will climb up the trees and lower canopies. This next weed is a real problem especially for those coastal forests. It is the climbing asparagus, Asparagus scandens. Now it has tubers which are a problem so when you're getting rid of it you've got to make sure you get those out. It's also got berries which the birds spread which makes it very invasive into the forests. Now it was introduced in the late 19th century as a bit of a climber and then also valued for its fern like foliage but it's a real pain and you need to get rid of it. Another pretty but invasive climber is the ochebean. Nice pink flowers, part of the peaf sort of family, the legumes and it has seeds that are very very fertile and of course the birds will spread those seeds as well. It's a very quick climber. It will grow up to those upper canopies and cover and smother them very quickly. These next plants are morning glory climbers. These couple of different species that are quite invasive. Of course this is the same genus as Coomera and so there are good plants in this genus but these ones are particularly invasive and problematic. They'll grow in part shade and sun and they are spread by little rooting stems and fragments. Established in 1800s as sort of climbers and ornamental but now have become a very invasive weed. So you've really got to cut those vines back, remove the and basically treat with herbicide. This is a warmer type of climber around about 8 to 11 zone. This is a very invasive weed. It's the moth plant. It's a major problem in New Zealand and it has pretty white flowers. Probably why it was introduced but those white flowers were also reported to stick moths in them. So that's also why it was introduced was to help control coddling which it didn't do. It just became an invasive weed. Now if you look at the fruit, those big large green fruits there, they are full of fluffy seeds that will be blown in the air and go and spread further. Now the vine itself has got quite a irritant sap so if you need to pull it out, you need to wear gloves when you're doing that. Of course you can treat it with herbicide also. Now these next weeds affect more of the understory of the native forest and this one is the bramble, the blackberry. It's a real problem. It has a way to climb up things and we looked at it previously so we're not going to go into too much more detail here but it is a problem weed. These next weeds are very problematic throughout most of New Zealand in the zones 7 to 10. Now you've got a couple of different types. You've got the tree privet. This is the Ligustrum lucidum and then you've got the Chinese privet, Ligustrum sinense. Both problematic. They both produce berries that the birds love and then will spread them to other areas. Now they have taproot so they're quite difficult to pull out so you need to get them when they're very little. Otherwise it's cut and paste with a herbicide. Now they were introduced as a sort of hedging plant but then obviously loved it in New Zealand so much that they spread all over and have now become a major major problem. This next plant, very invasive shrub, is the gorse and it's spread by seeds that basically have the pods that explode and propel these seeds out. Very viable seed that lasts a long time. Now we have got a couple of biological controls underway. There's the gorse seed weevil, the gorse thrips and the gorse spider mite all helping to sort of slow down the growth of this plant. It was introduced as a agricultural hedge but quickly managed to spread further afield. This is another highly invasive weed similar to gorse. This is scotch broom and it grows in the zones of five to eight so quite more likely to see this in the colder areas but there are a couple of biological controls in place. There's the broom psyllid and the broom seed beetle both help to reduce the vigor of this plant. Don't generally get rid of it completely but it has the same explosive seeds and a real problem as it spreads into a lot of land where natives would otherwise This is a problem in my garden. It's the woolly nightshade and actually I see this popping up all over the place. Highly invasive as part of the potato or the solanum family and it has quite a lot of seeds that are spread by birds and this is how it sort of sprouts up all over the place. Grows very quickly and it's one of those weeds that you have to sort of pull out especially when they're younger. They do develop a bit of a taproot and also it's a weed that you need to, if it's larger, then cut back and paste it. It grows in that zone nine to eleven so it's generally seen in more of the warmer parts of New Zealand. This is a plant that I've had in my garden. It is the Tradescantia. It's called the wandering willy and it will basically cover across the forest floor on the ground. Very thick covering. It is a plant that you need to pull out all of it. Even little tiny bits left that will re-sprout. Now that is a plant that grows in the slightly warmer parts of New Zealand in the zones nine to eleven so it won't be in those sort of colder areas of New Zealand. There are a couple of biological controls that have been introduced. One is a beetle which you can see in this video. I took a shot of it which was cool and also a fungus. Now the fungus is quite expensive. Ten plants cost around about six thousand dollars so hopefully that will become cheaper so people can actually use that to combat this plant. But it is a very problematic plant and it sort of wipes out a lot of those younger germinating seedlings on the forest floor. Now this is another plant that sometimes gets confused with that Tradescantia. This one is called the periwinkle. It's still an invasive weed this one but it's to point out there are a few that kind of look similar. This one has got a little sort of light pink flower on it and grows in similar sort of areas. This next weed is another plant that actually has a very nice flower to it. It's called the wild ginger. It's a plant that will grow in kind of shady sort of areas and likes it nice and moist. The flowers will produce a seed that the birds will then disperse which is a big problem and of course one of the big problems is it stops the forest regeneration because it really smothers that sort of forest layer. It grows in slightly warmer climates so at the zones from 8 to 11. This next weed is an invasive one on the forest floor. It's one I had in my parents garden. It's the Latifern Nephrolipsis Cordifolia. Now it has small round tubers which then sprout up these ferns and the fern will just smother and cover everything. Now it is a very hardy fern. It will grow in sun or in shade but it's a plant that really needs to be got rid of. It shouldn't be confused with the native fern Nephrolipsis flexiosa. That's a much smaller fern and it has much smaller tubers and not much of a problem. This is another very popular perennial plant. It's the Agapanthus. It is very very tough. It will grow in places that no other plant will grow. It will grow in shady places, sunny places, coastal places and of course it's got beautiful blue flowers. It's got sort of quite fleshy sort of rhizome roots which gives it that sort of extra ability to survive in the drought conditions. But it has a highly viable seed which then do spread. It will spread and then just get thicker and thicker, thicker clumps. So it's a weed that really needs to be dug out and if you're going to grow Agapanthus there are sterile versions that are available and those are the ones to go for. The Pampas grass is another one of these plants that just grows in a lot of disturbed ground. It is very fast to germinate. It's got wind-borne seeds which helps to sort of spread it. It is a plant that gets quite often confused with our own Toi Toi and but we've got this two main types here. It's the Cortaderia jubata and Cortaderia siluana and both problems and both need to be got rid of. One of the big problems is wilding pines. So there's lots of different pines that have got very viable seed and these are blown into different areas and pines generally grow very quickly. So they can quickly establish themselves as trees and become the dominant canopy and basically take out the more desirable natives. So this is something we've got to look at and sort of things like cutting and felling trees, removing the seedlings, treating the stumps to make sure we don't get a regeneration of these conifers that will come and actually take over the forest. The same goes of course for these exotic trees. Not all exotic trees are problematic but there are things like wattles, albizias, taiwan cherry, some sycamores and other plants that are just very very fertile seed and they will end up growing into those areas and controlling the canopy of native forests. So particularly bad ones I find are the albizia and wattles. They grow very very quickly and need to be pulled out as soon as you can. A lot of them do have tap roots so if you leave it too late it's quite difficult to pull them out and then just treat them with a herbicide like Roundup. Okay that wraps up our look at invasive environmental weeds, the ones affecting our native forests. Hopefully you enjoyed it and we'll see you in the next video.