Posted: 22/04/2013 at 15:13
Cestrum will soon become a weed in your garden, you may want to reconsider that one! You see it growing (looking very pretty there) all over old quarries and at the edges of football grounds etc.
Most seedlings need to be pricked out when they have 2 true leaves. In other words, remove them from their seed trays - holding the leaves, never the stems, by the proper leaves, and put into individual pots, probaby 3 inches or so, to grow on larger and stronger. This applies to all seed grown plants at that stage, Use a good, free draining compost with something like vermiculite to open it up. Keep moist - not wet. and they will grow on fine.
In due course you dahlias will go into the ground, or into pots as you wish, and provided you dead head them they will bloom for ages. In autumn you will find they have developed tubers, which you can dig up and keep to grow again next year.
There really is not room on this site to go into everything, I would suggest you get a good basic book - try your local library to find one that you like and speaks sense to you - and annotate it as you go along. Some things will work for you, other things you will adapt as time goes on and you find your own way of doing things as we all do.
Try not to try and do everything at once, you have hopefully years to get your new garden into whatever state you want it, don't try and do it all this year. Throw some annual seeda around and enjoy the flowers, while you concentrate more expertise as you learnit on the things you are really keen to do - veggies, fruit or whatever . Gardening is a long term thing, not to be 'finished' in a few weeks. We have lived here for 15 years and bits of the garden are just beginning to come together, the rest may do so over the next 15, or maybe not, we will see ..............