Tillage and soil disturbance brings one other thing to light – weed seeds. I can’t help but think about weeds at this time of the year since I’ve casually observed plenty of patches of weedy hell just traveling through residential neighborhoods.
Weeds will get away from you if you don’t stay on top of them. That’s just what weeds are consummately equipped to do thanks to their genetic heritage and reproductive strategy – live fast, die young, and crank out seeds in vast numbers. The seeds then bide their time near the soil surface until the conditions are right to replicate the growth cycle all over again.
The plant species we call “weeds” are really nothing more than plants we have judged as unwanted because they’re the wrong plants in the wrong places. For one thing, they tend to be non-native to the places that are being colonized. For another, weedy species tend to not encounter built-in biological controls that keeps their population growth in check in their native ecosystems. That means that nothing in their new host environments has learned to exploit the weeds as a food resource…yet.
For lack of natural controls to keep weed populations in check, it’s on us to impose that constraint in our gardens and landscapes. It’s late April now in Southern CA and the majority of weeds have set seed. The best time to set the weeds back is just after the first winter rains. Let the weeds grow up a bit but and then pull (deep tap rooted species like dandelion, wild radish, or cheeseweed) while the soil is still moist or mow them (grasses only) when they’ve set flower (inconspicuous on grass species) but don’t wait until the weeds set seed. Like many things in life, timing is everything. If you’re wondering why it’s not helpful to wait until the plants set seed, it’s because the seeds of some species are viable plant embryos long before they’re separated from the parent plant. When you wait, you inadvertently add to the weed seed “bank” in the soil.
Tillage makes things worse. Some weed seeds no doubt are killed in the process but the majority are just “warehoused” by tillage. It’s like putting them in the equivalent of a bank security deposit box. Without tillage, most seeds will remain at the soil surface. Ants carry some seeds away, earthworms consume other seeds and redeposit them in castings, and gophers and other animals move seeds through burrowing. Broad scale tillage helps foster an “out of sight, out of mind” mentality. Sure, the weeds for that season or that year may be gone but the seeds of their ancestors lie in wait to return with a vengeance.
Urban/Suburban Ecoliteracy 