Posted: 01/09/2015 at 17:26
Hi Linda, when you say 37 cm, is that diameter? The volume of the pot will determine just how much you put in.
Having said that, the rule of thumb for bulbs is that you bury them twice to three times their depth - a 2" daff will need about 4" soil above it, so the hole will be 6" deep. The smallest bulbs will therefore be nearest the top of the pot. If you have a mix, layer them according to size, but as most alliums are summer flowering, you might want to add some crocus or dwarf Iris in the top layer which will flower late winter/early spring.
If you want something to last right through till the alliums are ready, you could use native primulas. These will give you a display in early spring and the foliage will last well too. Mine flower on and off for ages. They prefer shade so you may need to have them in a slightly different spot - near a window is good so that you can see them - and then move the pot to a sunnier site when the alliums start to come through. Some of the grasses would also do the job. The more 'mop headed' kinds are ideal, like Festucas ( there are many blue varieties readily available) or Carexes (Evergold is a good green/gold variety). They will give you cover right through the winter and spring, and the alliums will grow through them.