It may be that after you’ve been out and had a look at the weeds in the places that you don’t want them that you only find a couple of species, but that was not my experience. On looking at a place overrun by weeds the response it can engender is “Aaarrge, pass me the sprayer!”. This is only a short term solution, and counterproductive in the longer term. So it is much better to understand what you are up against so you can develop a longer term, and more effective, weed management strategy. If you have a lot of weeds to manage, it can be helpful to be able to decide which weeds to attack first. The trouble is how do you work that out?
The PITA weed scale
That is why I developed the PITA (Pain In The A$$) scale that helps you look at each weed in turn and rate them in terms of invasiveness and persistence, assigning a number for each, the combining the two numbers to give you a figure out of 25. The higher the number the more of a PITA the weed is and the higher up the list for managing it should be.
There are a couple of other factors that may affect the score, which you can use if you want, but otherwise it is a fairly simple system allowing you to divide your weed list into weeds which are minor, moderate or major PITAs. Then off you go!
As mentioned above, the PITA scale takes into account the invasiveness of a weed, ie how quickly and effectively it can move into an area and take over, and persistence of a weed, being how difficult is it to get rid of. A slowly growing weed that stays in one place and is easy to pull out without leaving material behind that will re-sprout will have a low PITA score whereas a weed that goes rampant overnight and leaves seeds or runners in the ground which are difficult to dig out will be pegging the PITA meter!
Scurvey weed - it spreads via stolons and can be quite invasive
Invasiveness
This is the property of a weed to be able to move into an area and outcompete plants already there such as fruit, veggies and herbs etc.
5 Plant spreads by a combination of rhizomes/stolons/vegetatively and by seeding prolifically eg creeping oxalis
4 Plant spreads by rhizomes (underground runners) eg kikuyu grass or stolons (aboveground runners) eg Scurvy weed
3 seeds are spread by wind or people eg dandelion, cobbler’s pegs
2 seed are spread spread by explosive seed dispersal eg flickweed
1 Seeds are spread primarily by water movement ie they fall close to the plant and only disperse in heavy rain eg amaranth
Scurvy weed also can leave roots behind when it is puled out - allowing it to regrow
Persistence
This is the property of a weed that enables it to remain in place despite concerted actions to remove it.
5 The weed has underground rhizome, corms, bulbs that come up again when leaves pulled out eg onion weed, nutgrass
4 The weed regrows from broken stems & roots which occur as a result of attempts to remove it eg scurvy weed
3 The weed has a taproot which breaks off when pulled, allowing the weed to regrow eg dandelion
2 fibrous root system that does not regrow when pulled out eg paspalum
1 single stem, simple root system easily pulled out, does not regrow eg petty spurge
Other considerations
There are several other considerations which may modify the original PITA score which are not taken into account by the invasiveness/persistence weed criteria. It is up to you if you want to include these considerations in your calculations.
Is the weed useful in some way? Or, more importantly, is the weed useful in a way which you are likely to take advantage of? For example, dandelion is useful in that the whole plant is edible, it may have medicinal properties, the roots are used to make a coffee substitute and the flowers used to make a honey substitute. Of course, if you have no intention of using dandelion in any of these ways the PITA score would remain unaltered and it would be just another weed. However, if you do intent to take advantage of a weeds useful qualities (ie the weed is edible, dye, medicinal, a nitrogen fixer, a dynamic accumulator), this could be taken into account by taking 5 points off the PITA score.
On the plus side: scurvy weed is edible
Are you, or any of your family, allergic to this weed? Allergy, depending on how severe it is, could be pivotal factor on how important the weed is to prioritise for management, so the PITA score could be doubled to bring this point home.
So, the idea is, now that the weeds of concern have been identified, and then assessed as to their level of being a PITA, then next thing will be to research these priority weeds and decide on which management techniques will be used to reduce their impact.
