Rock Cress vs Creeping Thyme (Everything You Should Know)

Rock cress and creeping thyme are both low-growing, creeper plants. Both plants are great as edging plants or ground cover. Rock cress and creeping thyme produce colorful flowers throughout spring and summer.

Please continue reading for the complete comparison of rock cress vs creeping thyme. I will explain all the differences and similarities between these two plants.

Also read: Creeping thyme vs creeping phlox

Rock Cress vs Creeping Thyme: Comparison

	Rock Cress	Creeping Thyme
Botanical name	Aubrieta spp.	Thymus serpyllum.
Common names	Rock cress False rock cress Aubrieta	Creeping thyme
Native area	Europe	Europe
Plant type	Perennial, herbaceous	Perennial, herbaceous
Plant family	Brassicaceae	Lamiaceae (Mint family)
USDA Zone	4 – 9	2 – 9
Bloom time	Spring	Summer
Sun	Full or partial sun	Full sun
Soil	Well-draining soil	Well-draining soil
Soil PH	Acidic Alkaline	Neutral Alkaline
Toxicity	Non-toxic	Non-toxic

Is creeping thyme the same as rock cress?

No. Creeping thyme and rock cress are two different plants. They belong to two different plant families.

What is the main difference between rock cress and creeping thyme?

The main difference between rock cress and creeping thyme is the smell and the flowers. All thyme species including creeping thyme have a pleasant thymy aroma. Rock cress also smells quite good, but not like creeping thyme. The fragrance of rock cress is more noticeable on warm spring days.

Rock cress flowers are a little bigger than creeping thyme flowers. Also, the creeping thyme flower blooms in clumps of flowers, unlike rock cress.

Native area

False rock cress is native to southern Europe and central Asia. It is a common plant in gardens in Europe. Creeping thyme is also native to most of Europe as well as North Africa.

Both these plants have been introduced to other parts of the world such as the United States, Australia, and New Zealand.

Creeping thyme is more commonly found in North America than rock cress (Aubrieta).

Common names

The rock cress plant referenced here is commonly known as false rock cress or Aubrieta. But there is also another rock cress. It is called Arabis. However, these two are two different plants and not the same.

Creeping thyme has many common names. Breckland thyme, Breckland wild thyme, wild thyme, or elfin thyme are some of them.

Plant type

Rock cress is a low-growing ground cover that grows up to 6 inches tall and about 12 to 24 inches wide. Rock cress is a hardy perennial in most climates.

Creeping thyme is also a low-growing, subshrub creeping perennial that grows about 2 to 6 inches tall and 6 to 18 inches wide. This plant remains evergreen in warmer climates. But it will die back in areas with colder winters.

Flowers

Both plants produce colorful flowers. Rock cress has pink, purple, or white flowers. They start blooming in spring. The flowers are small and have four petals.

Creeping thyme also produces beautiful flowers. They also come in the same colors just like rock cress and usually start blooming in late spring and early summer.

Growing conditions

Sun

Both plants require full sun to thrive. But they will survive under partial shade. If they don’t get enough sunlight, they will start to lose their compactness and become leggy. Also, they won’t produce many flowers.

Creeping thyme and rock cress should get at least a few hours of direct sunlight. So, don’t plant them under large trees or other shady areas.

Soil

Rock cress prefers slightly alkaline (PH level between 6.5 and 7.5) rocky soil. You can make the soil more alkaline by adding lime to the soil. Having rich soil is not necessary. However, if the soil is really poor, add a handful of compost before planting.

Creeping thyme grows well in PH-neutral soil with some organic matter like compost. It also does really well on rocky terrains.

The most important thing in the soil to look out for when growing rock cress or creeping thyme is drainage. The soil should be well draining and should not stay wet. This is extremely important since wet and soggy soil can kill the plants. To increase the drainage, you can mix in perlite or sand to the soil.

Alternatively, you can use containers filled with well-draining potting mix.

Water

Both plants require consistently moist soil to thrive. However, the soil should not retain water too much. To avoid wet and soggy soil, water only when the top inch or so of soil is dry.

You will need to water more often in hot weather. Do not let the either of plants go dry for too long.

Temperature and humidity

Rock cress prefers cool temperatures, especially in summer. It doesn’t do well in extremely high temperatures. However, it can grow in high humidity.

Creeping thyme on the other hand can withstand higher temperatures but humidity. It doesn’t like highly humid areas. The plant can lose its leaves in such environments.

It is best to check for specific needs before planting since there are so many creeping thyme varieties.

Propagation

Rock cress

Rock cress can be propagated by either seed or by division.

Dig up the plant using a shovel and cut and separate them into single plants. Then replant in pots or in the ground (about 12 inches apart).

Propagation by seeds is also a great way to get a lot of plants. Remember, the seeds collected from hybrids won’t give you the exact plant. So, it is recommended to buy seeds from a seed company.

Buy Best Rock Cress Seeds

To propagate from seeds, please follow the instructions.

• Sow rock cress (aubrieta) seeds on a sterile potting or seed starter mix. I recommend you use a seed starter kit to increase the germination rate.
• Seeds need light to germinate. So, don’t cover them up.
• Keep the soil moist. Spray with water without disturbing the seeds.
• The temperature should be between 65 to 75 degrees Fahrenheit.
• The seeds will germinate within 2 to 3 weeks.

Creeping thyme

Creeping thyme can be propagated by seed, division, or by stem cuttings. Propagating creeping thyme can be done using seed or division just like rock cress.

If you are going with stem cuttings, make sure to use a sterile knife or scissors. Then apply a rooting hormone to the cuts. Then plant the stem in a pot with a well-draining potting mix. Water regularly and keep under partial shade. The stem should start to root and produce small leaves.

Pests and diseases

Rock cress

Rock cress that is growing in wet areas can be suspect to downy mildew. This is a fungal disease. To avoid this disease, plant rock cress in well-draining soil that gets plenty of sunlight. Spacing is also important since good air circulation can prevent many fungal diseases.

Root rot can also be a problem in poor-draining soil. Use soil with mixed perlite or sand to increase drainage.

Creeping thyme

Creeping thyme is also susceptible to root rot. Just use good soil to increase drainage.

Spider mites and aphides (especially in indoor plants) can attack creeping thyme despite its strong scent. You can spray them with a splash of water or use an organic pesticide to get rid of them.

Toxicity

Both rock cress and creeping thyme are non-toxic to humans, dogs, cats, and other pets. They are safe to plant in your garden.

Frequently Asked Questions (FAQs)

Last update on 2024-05-16 / Affiliate links / Images from Amazon Product Advertising API