It may be grown from seed which should be soaked in hot water and left overnight. You will see if this has been effective as the seed will swell up. Sow the following morning. Seedling trays with seedling mix can be used, or the seeds could be sown directly into black bags. Cover lightly with sand and do not allow to dry out. Germination usually takes 3 - 12 days. The seedling will transplant well in spite of the long tap root. Wait until they unfurl their second leaves before transplanting.
In cold and dry areas the tree will be deciduous.
The sweet thorn is very adaptable to soil types and is frost and drought hardy. However, for best performance, water well and deeply (shallow, frequent sprinklings only encourage shallow root growth) until established. Plant with plenty of compost, bonemeal or superphosphates (commercial tree tablets also work well).
The growth rate is fast, up to 1m per year. The growth on this bonsai was obtained in two months time:
Progression:
November 2009
August 2012
September 2011
November 2012 before cut back.
November 2012 after cut back - important to cut back again to last bud on twig.
The tree will be defoliated as soon as the new buds swell. From there it will be pinched regularly. In August 2013 it will be repotted in a bonsai pot.
More or less the vision I have for this tree.
The latest pics(October 2013):