Minus Thyme Needs to Be Divided

I bought 2 flats of minus thyme from you 2 years ago. I want to transplant some to divide them. In the soil is sand put there by the person who laid my flagstone. It does need more sand but I am not sure what type to buy or use to add more. Also the plants have turned black and look as if they are dying. Do you think it was this winter's damage or is there not enough of something .

Use sharp builder's sand to augment the soil put into the cracks between your flagstones. If your soil is heavy clay, the mix should be half and half of clay and sharp builder's sand.
Minus thyme is only winter hardy to zone 5. Here at Richters we have zone 5 and last (2007) winter, when it finally came, was a zone 4 winter. This thyme would have died here. The death would not be apparent until the plant had time to thaw out and then would turn black with rot, since it was dead. If you suspect that your winters may be too severe for this thyme, I suggest that you plant purple carpet lemon time instead. It is very hardy. If minus thyme is just a bit too tender for your growing area, I would suggest that you mulch your patio with straw for the winter and that may be just enough to make the plants survive since it cuts down on the freezing and thawing they have to try to survive.