Don’t pull up your weeds!

We all like a tidy garden, myself included but a year or so ago, I learned a valuable lesson that Nature has been trying to tell me for ages. I’d put it to the back of my mind but now that we’re starting to prepare for Autumn/Winter (or the closest thing to them that climate change will let us have), I’m reminded that Nature, too is preparing. For insects, the preparation and down time is called ‘overwintering’.

In all my research on insect and predators, one thing eluded me, ‘where do they come from’? Sure, they come from eggs but where do the first of the season come from? Is there some magical place outside of Ligaya Garen? Do they live their lives in other people’s gardens and come to ours when the Broccoli are planted out?

Parasitoid Wasps hatch when Aphid populations are large enough.
Parasitoid Wasps hatch when Aphid populations are large enough.
Stethorus wait somewhere until Spider Mite populations build up.
Stethorus wait somewhere until Spider Mite populations build up.

For all my talk of integration of aspects of the garden and my knowledge of weeds, I had one blind spot…

In my tidying up efforts at the end of the seasons, I was removing weeds and finished plants and returning them to the soil. Doing so, I have been removing the shelters for the critters, both good and bad (from a conventional gardening point of view) and destroying the places where they could safely survive the off season when they weren’t munching on my veggies.

It makes sense that they would lay the end of season eggs on the same kind of plants they like to eat. Even though the individual plant that they lay ‘sleeping’ upon was dead, the odds are that, next year, more of the same plants will grow a short crawl, jump or flutter away, ready to start breeding on. Maybe some survived as larvae or even adults. All of that turned out to be true.

My epiphany came when I was researching Australian Admiral Butterflies. They lay their eggs on Nettles, which are, here, annuals. Their larvae eat the nettles, pupate on them, hatch and fly looking for other Nettles to lay their eggs on.

Australian Admirals rely on Nettles.
Australian Admirals rely on Nettles.

One day, when I was out looking for larvae so that I could identify them accurately, I spied a Spined Soldier Bug attacking one. At the end of that season, I found Bug eggs on those plants that were probably from a Spined Soldier Bug (I’m still learning egg identification). There were other eggs that I couldn’t identify at the time.. The last of the season’s larvae of these beautiful butterflies overwinter on Urticaceae and often adults overwinter too but I’m not sure where.

Spined Soldier Bugs are a predat5or of Yellow Admiral larvae.
Spined Soldier Bugs are a predator of Yellow Admiral larvae.

These eggs were on a withered, drying plant and then it fell into place… both of these species, prey and predator need the Nettles to survive the inactive season. They could then kick off the next year’s activities when the season was right.

It’s very important to keep Soldier Bugs around. In our area, they’re predators of Flea Beetles and Cabbage (Diamondback) Moths, Corn Earworm, Armyworms, European Corn Borer, Cabbage Loopers, and probably many others that I’m unaware of as yet.

The Australian Admiral is a great example of adaptation. As a native Australian species, they didn’t have access to weedy Stinging Nettles until European colonisation, there are other plant species in the same Family as Nettles (Urticaceae) that they lived on but when they discovered Stinging Nettles, things soon changed for the better!

We all know that Monarchs love Milkweed.
We all know that Monarchs love Milkweed

A little after that, I learned about the ecosystems that grown around Milkweed in which Monarch Butterflies, Hoverflies, Parasitoid Wasps and Milkweed Aphids all co-exist on Milkweed plants throughout the year. The pests hatch first and when the population is about large enough, something triggers the hatching of the predators.  

Monarch larva and Milkweed Aphids on Milkweed.
Monarch larva and Milkweed Aphids on Milkweed.

The lesson from all of this is to leave some of the weedy plants in your garden and not to pull them out. The same goes for your plants that have passed their use by date – leave a few Brassicas around, for example, to kick off both the Aphid, Caterpillar and more importantly, Wasps next year.

Like a lot of gardening techniques that I’ve learned through observation, this may seem counter-intuitive. We are raised to believe that a tidy garden is a good garden and that weeds bring pests. Of course they do, but take it one step further – weeds bring predators too!

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