Why did that weed come back up in my lawn?

Selective herbicides (the ones you use on lawns) will state on the packet which weeds it will target and kill. These weeds absorb the herbicide and die. It can take up to two mowing cycles. That means if you mow weekly, it will take two weeks to have an effect; if you mow every three weeks, you will see its effect in six weeks. You spray, they die.

‍

Now, a few months later, you see them again; these are the seeds they produced, now sprouting. Every time you notice a clover, creeping clover, Bindi, dandelion, oxalis, or thistle growing, the flower often draws your attention. Those flowers quickly turn to seed and spread through the lawn. They hitchhike on shoes, mower tyres, pets and even us. Those seeds can sit dormant until the conditions suit them with warmth or rain to germinate.

‍

It is not the parent plant that has resprouted but the thousands of seeds they have distributed. That is why, on many selective herbicides, they may say to respray at a set time to get the germinated weeds before they are mature enough to develop seeds themselves.

‍

Have you ever noticed the creeping oxalis, the yellow flowering with a clover-like leaf in your pots, gardens, and lawns? They have explosive seed pods, which contain five compartments and within each compartment, there are several seeds; this is just from one flower alone. It only takes one flower to mature, and they fling the seeds with force to start reproduction, making it so hard to get rid of; you kill the parent plant, but the seed can sit and wait for optimal conditions to torture you again. Think of your pot plant; one pot has creeping oxalis and spreads to the pots below and around it when the seeds are released. It can take time and dedication to kill weeds in the lawn.

‍

It is a repeated process for most gardeners, but the weed numbers will reduce.

‍