Tag Archives: garden weeds

Our worst weeds

After advocating for wildflowers on our road verges in January, it is perhaps ironic that I follow up with the worst weeds in our garden. All are ornamental garden escapes and none should be liberated to roadsides.

Cape Pond Weed

Cape Pond Weed

There are times Mark has wanted to line up and shoot the former neighbour upstream from us who deliberately planted Cape Pond Weed – also known as water hawthorn, botanically Aponogetum distachyum. Pretty it may be in bloom, but we have been waging war on it for well over a decade. Floods scoured it out upstream but it has made itself right at home in our slow moving sections. We spend countless hours raking it out each summer because it we don’t, it will only take one full season before it covers the entire water surface. Miss one piece and it grows away again at an alarming speed.

Prunus campanulata filled with tui

Prunus campanulata filled with tui

Prunus campanulata ranks amongst our two worst weeds. We are constantly pulling seedlings out, or digging if they have snuck through to a second season. Any older than that, and they require poisoning. Yes I know some folk think we should get rid of all of these but the tui! The tui! And please do not tell me to plant kowhai for the tui instead because they don’t flower at the same time and even our largest kowhai trees cannot sustain the scores of tui that frequent our early blooming Taiwanese cherries. So we continue to deal to the unwanted seedlings on an ongoing basis.

There is hope. Mark has been turning his attention to the sterile campanulatas we have here, because it is the seed that is the problem. His father bred sterile campanulata hybrids – ‘Pink Clouds’, ‘Mimosa’ and ‘Petite Pink’. The last variety is probably not commercially available now which is a pity because it is a true dwarf tree. The problem with all three varieties is that they are candy pink, not the sought after carmine red. But we have a few sterile reds with some possible options which give flower power and nectar for the tui without the curse of seed.

About the bangalow palm's seeding ways...

About the bangalow palm’s seeding ways…

The other shocker – maybe I had better whisper this, given its popularity – is the bangalow palm (Archontophoenix cunninghamiana). Yes it is handsome and reliable but this Aussie import is far too keen to make itself at home. It took a long time for our specimens to start flowering but boy, are they a problem now. Mark tries to cut the seed off as soon as it is visible, but this requires the extension ladder and a pole saw. There is probably not a square metre left in our garden where we have yet to find a germinating bangalow. What is particularly concerning is that in the early stages, they are very difficult to pick apart from seedling nikaus. If you are anywhere near native bush or reserve, this is one plant that you should question having in your garden. Based on our personal experience, we recommend the Queen Palm (Syagrus romanzoffiana) as an alternative.

Mark adds in Cornus capitata, the weedy dogwood. It was favoured by his father who planted it all along one of the road frontages and Mark has been battling it ever since. At least it makes good fire wood.

Fuchsia boliviana performs TOO enthusiastically in our climate

Fuchsia boliviana performs TOO enthusiastically in our climate

We have reviewed pretty Fuchsia boliviana. We acquired it before it appeared on the National Plant Pest Accord but never moved it into the garden. Thank goodness. In the wilds of the “plant out” area, where some specimens can languish for years while waiting for the right spot to be found, it grew far too vigorously and the carpet of seedlings rang loud alarm bells. It is another of those plants where a sterile form would be advantageous because it flowers for months on end, is showy and has attractive foliage.

Dare I mention the wonderfully fragrant Himalayan Daphne bholua? It is not in the same league as the previous plants but it has certainly seeded down all round the place here. Not all the seedlings flower, either, which is not to their credit. It is another example of a plant which is highly prized internationally but can become a significant weed in our benign climate.

It can be a mighty fine line between a desirable self-seeder and a weed. Most of the plants mentioned produce berry-like seeds which are then distributed by the birds, particularly the kereru. Plants which only seed down close to the parent are manageable but once our feathered friends are on the loose, it becomes a different matter altogether.

First published in the March issue of NZ Gardener and reprinted here with their permission. 

In the garden this fortnight: Thursday February 9, 2012

A fortnightly series first published in the Weekend Gardener and reproduced here with their permission.

The only justification for growing seeding campanulata cherries - feeding the scores of tui in late winter

The only justification for growing seeding campanulata cherries - feeding the scores of tui in late winter


A rash of germinating campanulata cherries

A rash of germinating campanulata cherries

We are very cautious about invasive plants here. I know there is an old cliché that says a weed is just a plant in the wrong place but in a large garden, we can’t afford to have out of control triffids. If a plant starts to look dangerous, it probably is. If it is a prolific seeder and the seed is dispersed by birds, it is even more problematic. The campanulata cherries fall into this category and if it weren’t for the scores of tui they attract to the garden each spring, we would do away with them. The seeding bangalow palm (Archontophoenix cunninghamiana) is also a source of angst. The same goes for the Himalayan Daphne bholua which doesn’t just seed. It also suckers below ground. If we lived near a national park or adjacent to a native reserve, we would feel morally obliged to review our hospitality to these ornamental plants.

We are nowhere near as tolerant of wayward perennials and annuals. Forget-me-not may be pretty but it is aptly named. We have been weeding it out for years here and still it stages a comeback. The orangeberry (Rubus pentalobus) had to go when it formed an impenetrable mat after just one year then started climbing and leaping to extend its territory – but never fruited. Some of the ornamental tradescantias (wandering willies) are also invasive. We have a very pretty blue flowered form but it sets prodigious quantities of seed and is popping up in thickets many metres away. The remains of the arum lily Green Goddess still require regular attention to get rid of the last remnants of tiny rhizomes out of the ground.

Where we have plants which set miles too much seed, like the granny bonnets (aquilegias) and the sweet williams (dianthus), we try and deadhead straight into a bucket. From there, they either go to the bottom of a hot compost heap, out with the rubbish or on the burning heap. Composting alone does not kill seeds unless you manage your compost in a way that generates considerable heat. While we don’t mind a certain amount of seeding down of pretty plants, we like to keep them confined to particular areas and don’t want to spread them everywhere when we use the compost as mulch.

I am very fond of eryngiums

I am very fond of eryngiums

Top tasks:
1) Persuade Mark to head out with the chainsaw and cut down some of the self seeded pongas. We don’t regard these as weeds because they are native, but we end up with too many of them. We have them as raised beds in the rimu avenue, where some are now 50 years old. I want to extend the constructions along further and feature more bromeliads. I have never learned to use a chainsaw and am terrified of them. Mark is equally worried by what I could do with one if I became confident so has never encouraged me to learn.
2) Mark has been raising perennials from seed in the nursery and I need to get onto planting these out. I was particularly pleased to see a tray of eryngiums – blue sea holly. It is a little bit prickly but so very pretty. Blue flowers are my absolute favourite. It would have been better had we got onto planting these out earlier but they are perennial so should grow on to star next summer.

Ponga (tree fern) trunks, used to make raised beds andwhich have lasted for five decades already

Ponga (tree fern) trunks, used to make raised beds andwhich have lasted for five decades already