Herbicides help one person do the work of many. But they should be treated like strong medicinal drugs, to deal with a deep-seated problem once and for all. With patience we can do this naturally, with less damage to Earth and a more robust result – but another post for that.
Sometimes managers are impatient. Recently a herbicide (triclopyr + picloram) proved an enormous problem. Picloram is a residual herbicide (stays active in soil) used to control scrub weeds. Bad advice was given the manager as this chemical acts against many of the plants I intended to use – the assumption was the consultant did not need to be informed – a result of a siloed company culture.
As part of design I get to know a site by visiting in different conditions to find micro-climates, opportunities and problem areas. I soon noticed several weeds ‘missing’
- gorse and broom (Ulex europaeus and Cytisus scoparius – in the Fabaceae or bean family)
- wild carrot (Daucus carota in family Apiaceae)
- poroporo (Solanum laciniatum in the Solanaceae – the nightshades)
Plant families are important as herbicides fall into about 25 chemical groups that mainly function along plant family lines. These chemical pathways are very rare – the last decade has unearthed a single new one!
After some sleuthing it turned out that Grazon DS had been used – this contains picloram and is residual for two-to-five years. Herbicides are registered for specific uses, although as restoration plantings are not part of this process the effect of a given chemical on native shrub species is a matter of educated guesswork, industry friends (and deep searches on Google scholar).
Presence of picloram on site resulted in:
– Removal of several species from my planting mixtures
– Redesign of planting plans
– Doubling of project cost (as it nixed an alternative low-cost planting approach)
– A two-year delay in successful plant coverage
– A hold on growing some species at all within a five-year time-frame
This site has 5 millionths of a gram in every square metre: not much but enough to frustrate successful outcomes for many years.
My preference would be to plan ahead with land management, then a site can be planted using natural (and lower cost) means – it is a way we will have to re-learn as weeds evolve to handle our assaults.