Rosemary vs Thyme: Shrub Versus Groundcover Herbs
Rosemary vs thyme is a common question for herb gardeners. Both are woody, aromatic perennials that like full sun plus well drained soil. Rosemary grows as an upright shrub with needle like leaves. Thyme stays low plus spreads, with tiny oval leaves on wiry stems.
The short answer
Rosemary is an evergreen shrub that can reach 4 to 6 feet tall in warm zones. It is not reliably hardy in zone 6 or colder. Thyme is a low, almost prostrate perennial about 6 to 12 inches tall. It is frost tolerant plus works as an edging or groundcover plant.
How do rosemary and thyme grow differently?
Rosemary is a perennial evergreen shrub in zone 8 plus warmer, per University of Illinois Extension. Plants can grow 4 to 6 feet tall. Some varieties have a trailing or spilling habit. UF/IFAS notes rosemary can reach 4 to 5 feet wide in the ground. Its foliage is dark green plus needle like, resembling a spruce or fir.
Thyme is a low growing, wiry stemmed perennial. University of Illinois Extension describes it as 6 to 12 inches tall with small, oval, gray green leaves. NC State Extension notes common thyme forms a mound 6 to 16 inches wide. It is a bushy subshrub on a woody base.
| Trait | Rosemary | Thyme |
|---|---|---|
| Habit | Upright evergreen shrub, some trailing forms | Low mound, almost prostrate |
| Height | 4 to 6 feet | 6 to 12 inches |
| Leaves | Dark green, needle like | Small, oval, gray green |
| Winter hardiness | Not reliably hardy in zone 6 or colder | Frost tolerant |
| Easiest start | Stem cuttings | Divisions or cuttings |
Source: University of Illinois Extension plus NC State Extension.
Which is more cold hardy?
Thyme is the hardier herb. NC State Extension notes common thyme is frost plus drought tolerant. Poorly drained soil over winter will shorten its useful life, per University of Illinois Extension.
Rosemary is a tender perennial in the Midwest. University of Illinois Extension notes it often does not overwinter outdoors there. The variety Arp is one of the more cold tolerant types, perhaps to zone 6. Grow rosemary in containers so it can come indoors just before a frost.
Can they share a bed?
Yes. Both prefer full sun plus well drained soil. UF/IFAS notes rosemary needs at least six hours of sun. It declines when watered too often. NC State Extension notes thyme does well in dry, sandy or rocky soils with a neutral to alkaline pH.
Set rosemary at the back of the bed. Use thyme as a border or edging plant in front. University of Illinois Extension notes thyme makes an attractive border in the perennial garden. Its flowers draw bees plus butterflies, per NC State Extension.
How to: step by step
- Choose a full sun spot with well drained soil.
- Start rosemary from stem cuttings, since seed germinates very slowly.
- Start thyme from divisions or cuttings.
- Water both sparingly plus let soil stay on the dry side.
- Grow rosemary in a container where winters are cold.
- Cut thyme back hard in spring every few years to renew it.
Troubleshooting
Rosemary tips turn brown indoors: dry indoor air. Set the pot on a saucer of wet pebbles plus mist it often.
Rosemary roots rot: too much water. Let the soil dry between waterings.
Thyme turns woody plus leggy: older growth. Trim it in early spring plus summer to reduce woody growth.
For related reading see cannabis leaf anatomy, companion plants when growing marijuana plus what roles do bees play in outdoor cannabis. Kind Seed Co also stocks cannabis seeds.
Sources
- Rosemary, University of Illinois Extension
- Thyme, University of Illinois Extension
- Rosemary, UF/IFAS Gardening Solutions
- Thymus vulgaris, NC State Extension Gardener Plant Toolbox
FAQ
Can rosemary survive winter outdoors?
It depends on your zone. University of Illinois Extension notes rosemary is a perennial evergreen shrub in zone 8 plus warmer. It is not reliably hardy in zone 6 or colder. In those areas, grow it in a container plus bring it indoors just before a frost. Arp is one of the more cold tolerant varieties.
Can thyme be used as a groundcover?
Yes. NC State Extension lists common thyme as a spreading groundcover that suits rock gardens, borders plus walkways. It forms a mound 6 to 12 inches high plus 6 to 16 inches wide. University of Illinois Extension notes Wooly thyme forms a low carpet of gray leaves that suits rock gardens.
Do rosemary and thyme grow in pots?
Both do well in containers. University of Illinois Extension advises growing rosemary in containers in cold areas so it can move indoors for winter. Indoors it prefers a cool, sunny spot. Thyme can be potted in fall plus grown all winter in a bright, sunny spot. Use a pot with ample drainage for both.
How do I harvest these herbs?
Cut rosemary tips plus foliage as needed through the growing season, per University of Illinois Extension. Pruning encourages a tight, compact habit. Cut thyme just before it flowers. NC State Extension advises cutting five to six inches off the top growth plus leaving the woody stems. Always leave five inches of growth.
Can rosemary grow from seed?
It can, but it is slow. University of Illinois Extension notes rosemary seed germinates very slowly. The resulting plants may take years to become useful. Stem cuttings root easily plus grow quickly. UF/IFAS suggests buying rosemary plants from a garden center, since starting plants from seed or cuttings can be difficult.
