What is a weed?
There are many definitions of a weed. Most come down to a plant in the wrong place. What counts as a weed depends on your perspective. A conservation worker, someone working from te ao Māori, a farmer, or a community group restoring a local reserve may each see it differently.
SWAT takes a broad approach. It treats any exotic plant species that turns up in the wild as a weed. Not all of these will settle and spread, or become invasive.
What is an ‘emerging’ weed?
SWAT also takes a broad approach here. An emerging weed is any exotic plant species that turns up in the wild. Not all of these will settle and spread, or become invasive.
The general ‘tens rule’ suggests that about 10% of introduced species become established. About 10% of those then become pests. So only a small share of exotic plants that appear in the wild go on to cause serious problems.
Can native plants be weeds?
By the broad definition above, yes. Some species are native to one region and weedy in another. For example, Pomaderris kūmerahou is native only to the North Island. It is treated as a weed in the South Island and is on the Tasman–Nelson Regional Pest Management Plan (RPMP).
SWAT only includes non-native species, so it will not alert you to native species. Contact us if you find a native species in your alert.
How bad is this weed?
How serious a weed is depends on two things. First, how easily it can establish and spread. Second, the harm it may cause if it becomes widespread.
Some weeds can quickly invade natural areas, farmland, waterways or towns. Others spread slowly or have only minor effects. Possible impacts include pushing out native species, cutting farm productivity, changing habitats, blocking access, and risks to people or animals.
There is no single measure of how 'bad' a weed is. Risk can also differ between regions and environments. A plant's biology, overseas weed history, distribution and known impacts can help you assess it. Local knowledge and expert judgement still matter. For more detail, see the Weed risk assessment page.
What is weed risk assessment?
Weed risk assessment is a way to judge how likely a plant is to establish, spread and cause problems in a particular area. It looks at whether the plant can survive local conditions. It also looks at how easily it spreads, the impacts it could have, and whether it has been invasive elsewhere.
No method can predict future behaviour with certainty. Weed risk assessment still helps identify species that may need monitoring or management. For more detail, see the Weed risk assessment page.
Why do different weeds have the same common name?
Common names are informal. The same name is often used for different plants in different places or contexts. One plant may also have several common names.
SWAT uses the scientific name as the main identity for each taxon. Common names are shown to help recognition, but they are not unique.
Why is the scientific name different from the one I usually use?
SWAT follows the naming used by GBIF, based on the Catalogue of Life. The name accepted worldwide can differ from the name commonly used in New Zealand.
Older or local names are often treated as synonyms of the accepted name. Searching by a synonym should still find the accepted name in SWAT.
Are seaweeds and algae included in SWAT?
SWAT includes all Plantae species. That includes green and red seaweeds, but not brown seaweeds. SWAT also includes the weedy wakame (Undaria pinnatifida).
Green and red algae are in the Plantae kingdom. Brown and other algae sit in other kingdoms. See Seaweed.ie’s overview of algal kingdoms and the Coastal Wiki page on marine algae.
Besides Plantae, SWAT includes the weedy algae didymo (Didymosphenia geminata). It will include lake snow (Lindavia intermedia) when that name is added as its own species in GBIF.
What does × mean in a species name (eg Berberis × bidentata)?
The × symbol (a multiplication sign, not the letter x) shows that the plant is a hybrid. It is a cross between two different parent taxa. For example, Berberis × bidentata is a hybrid barberry.
What happens if a weed has a name change?
We will update any alerts you have to use the new name, and we will email you so you are aware of the change.
How often does SWAT get new weed records from GBIF?
SWAT downloads weed records from GBIF daily.
How long will it take for iNaturalist observations to show up in SWAT alerts?
iNaturalist only publishes research-grade observations to GBIF. These may take one to two weeks to appear after they reach research-grade status. Alerts are then sent on the next weekly alert run.
Do alerts come out in real time?
No. We batch alerts. They are currently scheduled on a weekly basis.
Why am I being notified about historical records?
The event date in SWAT is the date the weed was observed or collected. That can be many years earlier than when the record reaches SWAT.
Herbaria and other publishers often digitise old specimens and publish them to GBIF years after they were collected. New publishers may also share older datasets for the first time.
For iNaturalist, an observation is only published to GBIF once it becomes research grade. An old sighting may only now have been identified and verified.
Why aren’t I getting any alerts?
There may be no new matching records. Your alert settings may also be filtering records out. For example, if you set a maximum of 10 occurrences, you will not get alerts for species that already have more than 10 records in your place.
With that option, you only get alerts while a species has fewer than your chosen number of records in the chosen time period. Species already over that limit, and those that later go over it, will not trigger alerts.
Why does my alert show more than 10 records when I set a limit of 10?
The limit is checked against the count before this alert's records are included. Say a taxon already had 9 records and this alert adds 3. The total shown will be 12, but the alert still sends because 9 is below your threshold of 10.
After this alert, you should not get further alerts for that taxon unless the count drops again. This could happen if records are deleted or fall outside your other settings.
Why am I getting an alert that is outside the places I defined?
A weed record is included if its location uncertainty overlaps your place plus the buffer distance in your alert. Records with a location uncertainty above your maximum setting are left out.
Why have I suddenly received an alert with a very large number of new weed records?
A large dataset may have been uploaded to GBIF. For example, a herbarium may have loaded many historical records. Publishing of records from eDNA analysis can also add a large number of records at once.
What happens if GBIF records are updated, deleted or re-identified?
When a publisher updates or removes a record, SWAT keeps its copy in sync.
For updated records, you are only alerted if the taxon name has changed, for example if a record is re-identified as a different weed. Other updates, such as a corrected location or date, are applied in SWAT without triggering an alert.
If a weed was incorrectly identified and later corrected after it had already triggered an alert, that earlier alert will still contain the weed. SWAT then marks the weed record as deleted for the original identification. The weed record count is reduced when SWAT checks whether to stop alerting you. This only matters if your alert is for 'New or uncommon weeds', or you have selected the 'Stop alerting me' advanced setting.
For deleted records, SWAT removes the record and marks it with a note that it has been deleted. A record may disappear because the publisher removed it from their dataset, for example if it was published in error or is a duplicate. For iNaturalist, the observation may have been deleted. It may also no longer meet the criteria for a research-grade observation, for example if it has been reclassified as cultivated rather than wild.
Will SWAT alert me to ‘cultivated’ (planted) records from iNaturalist?
No. iNaturalist records marked as cultivated do not reach research-grade status, so they do not feed into GBIF. Only research-grade records do.
You can set an alert in iNaturalist for any new records of a particular species and place. Go to Subscriptions > Subscribe to a place, then select the place and taxon. That can include cultivated records.
Other publishers, such as herbaria, do provide cultivated records to GBIF.
How do I see past occurrences from my alerts?
You can view past records on the map on each species page for the weed species in your alert.
We are adding more maps to make this easier. In the meantime, contact us if you would like an alert email generated for past occurrences of your alert.
How do I control this weed?
- Confirm the identity of the weed. View the original weed record on GBIF and verify the location and species.
- If it's not on your land, get permission from the landowner.
- Assess and reduce any risks, and follow any restrictions set by the landowner.
- Check for a specific Weedbusters guide for the weed species.
- Refer to the Weedbusters guide on controlling weeds for general guidance.
How can I help?
- Be curious. If you see a plant you don't recognise, take a photo and upload it to iNaturalist. Once it is positively identified and becomes research grade, it adds to our database of weed records across New Zealand.
- Tackle weeds on your property. Use our links to Weedbusters to find out how to control specific weeds.
- Get involved with weed control and native restoration groups in your local area.