Posted: 03/02/2013 at 21:00
Before you start nipping folks, what do you make of this from the Black Country Society (http://www.blackcountrysociety.co.uk/articles/gardening/sweetpeas.htm)?
'If you plant the seed in a pot of good compost beginning of February, water well, cover with cling film keeping them at 60/65F., then when the plant has produced six full leafs, cut them back so as to leave four leaves on the original plant, the piece you have cut off is extremely valuable since it contains the leader cell growth, in affect stem cells, dip this in hormone powder, and stand in a jar of water the hormone powder will stimulate growth to the extent that it will have a stronger root complex than the original plant, you do not have to use water you can plant direct into compost but you will not have the benefit of watching the root growth which takes 10 days, no other part of the Sweet Pea will allow cuttings. The most important thing is you must water the leafs every day until the roots appear'
Read the link, Carly. Some of the content is valid (IMHO) other bits are just twaddle.
It may be worth noting that when the growing tips have been nipped out, they can be potted-up and the rooting success rate is quite good....plants for free!