How can I stop my nasturtiums getting killed by blackfly?

[BarnOwlFlying]

I know people grown nasturtiums as a sacrificial plant to protect their veg, but I want to grow nasturtiums as a pretty flower, plus as a nice edible flower/leaf. I’ve got a pretty watering can I use as a planter and I want them spilling over onto the patio just outside the kitchen, looking gorgeous.
Every year I try, they are just decimated by black fly, caterpillars or aphids.
I’ve tried washing up liquid spray.
How can I successfully grow nasturtiums?
Thanks.

For me the ones in the semi shade (sun 2-5pm) last longer than the ones in full sun. No blackfly in the shade at all. However, the large white butterfly caterpillars are having a great time...

It’s frustrating isn’t it.
I wondered if there was a sacrificial plant for sacrificial plants!

It’s frustrating isn’t it.
I wondered if there was a sacrificial plant for sacrificial plants!

We grow them FOR the caterpillars (and thus butterflies) they bring to the garden!

Oh don't get me wrong, I don't mind the caterpillars and leave them be (and the cute little yellow eggs). It mostly stops them eating the gooseberry leaves. I definitely prefer them to blackfly, and the nasturtium grows faster than they can eat it.