There are over 300 thyme varieties in the mint family of Lamiaceae, of which thyme is a member.  Many find this very confusing when choosing a variety to use either as a ground cover, or between flagstones, etc.  The purpose of this short article is to explain some of the differences and similarities.  Only the creeping-type varieties are covered here, not the uprights or culinary varieties.

First, a bit of how/where it grows: 

Most thyme varieties are hardy in USDA zones 5-9.  However, most creeping varieties do not like hot, humid summers or overly wet conditions. Most varieties prefer full sun and well drained soil. Avoid over-fertilizing thyme or it may become leggy and weak.  Most varieties of creeping thyme will resent overwatering, so soggy locations should be avoided.  Creeping thyme will tolerate, or sometimes even thrive amid moderate to severe pruning.

Varieties: 

There is always some confusion here!  Most, but not all, creeping types are a strain of Thymus serphyllum.  However, height, spread, and bloom color is not the same.  In some cases, vastly different!  To add to the confusion, Mother of Thyme is also sometimes known as Thymus Praecox rather than Thymus serphyllum!

Also keep in mind that leaf size will vary according to variety with Thymus serphyllum. 

Big Leaf, or Broadleaf is the most robust and rugged, but may be too tall for some uses.

Below is a simplistic chart of the varieties we grow and their traits.

Common Name Latin Name Height Spread Flower Color Comments
Big Leaf or Broadleaf Thymus pugeloides 4″ 12-18″ Purple Very fragrant and rugged.  Can also be used as culinary
Lilac Carpet Thymus serphyllum 3″ 10-16″ Lilac Not as short as Magic Carpet.  Also has slightly larger leaves.
Magic Carpet Thymus serphyllum 2″ 10-12″ Carmine Pink Shortest of the creeping types
Mother of Thyme Thymus serphyllum 4″ 12-18″ Purple spikes Thymus Praecox also known as Mother of Thyme
Mother of Thyme Thymus Praecox 4″ 12-18″ Rose-purple Thymus serphyllum also known as Mother of Thyme
Common Creeping Thyme Thymus serphyllum 3-4″ 12-16″ white to lilac Rugged type often used between flagstones
Red Creeping Thymus serphyllum 2-3″ 10-12″ Dark Pink to red  
Wooly Thymus pseudolanuginosus 2-3″ 10-12″ Varies Common variety name is Elfin.