Pinching out seedlings

I've got some dahlia piccolo and salvia seeds growing on my windowsill.

The dahlias started growing really quickly and are shooting up and the salvias are just starting to shoot.

I believe I need to pinch out seedlings to get them to bush out. Do I need to wait until they are a bit stronger? The dahlias are probably one to one and half inches tall and only have one set of leaves. The salvias are too small to do anything with yet.

I grew some seeds last year and managed to get about 3 plants out of them and they are tall and scraggly. I didn't know then that they needed pinching out!

 

In would only pinch out when the plant is established with about 4 sets off leaves . In the case of Dahlias when they are over 12" tall should be OK . As a rule of thumb I would say after about 6 weeks of the plant germinating or sprouting. I don't know if it does any damage pinching a plant too soon ?

 

Most Salvia species I wouldn't pinch out. What species are you growing?

 

Er, from memory Salvia Blaze of Fire - is that the species? I'll check the seed packet when I get home.

 

It's the cultivar. The true species would be S.splendens, this is a selected short form. It's not hardt so pinch them out at 10 to 15cm. But don't pinch, use a sharp and clean stanley knife and use the tips as cuttings for more plants.

 

Great, thanks, will do that!

 

How do you know which plants can or cannot be pinched ?
Generally if a plant is looking bushy and in proportion I would leave it . If it is looking lank and spindly or is getting a bit big and top heavy , in the plant pot before planting out in May , then I pinch them quite hard. Seems to work for me

 

Thanks. So much to learn! I have been 'gardening' since last summer but did not know about pinching. That might explain a few things!