Acanthus montanus — a medium houseplant, prefers full sun light
SPECIMEN · FROM THE LIBRARY
Acanthus montanus

Acanthus Montanus

Updated · 80 observations
ON THIS PLANT

Acanthus montanus, also known as bear's breech or mountain thistle and in Igbo; ogwu_ahga (in Agbani, Enugu State Nigeria), is a thinly branched perennial with basal clusters of oblong to lance-shaped glossy, dark green leaves reaching up to 12 inches (30 cm) long. The leaves have silver marks, wavy margins and thorns. It reaches up to 6 feet (1.8 m) tall and about 24 inches (61 cm) wide. Spikes of pale pink flowers appear summer to fall. It prefers shady situations and occasional deep watering, but tolerates sunny, dry situations too. Its aggressive roots make this plant perfect for slopes. It is native to tropical areas in western africa.

A note from PlantMom

Mountain thistle is fairly disease-resistant and generally not prone to illnesses. However, it can be affected by pests and diseases present in its environment. These issues are typically mild. In terms of care, the plant requires moderate maintenance. It should be pruned regularly to preserve a good appearance and promote healthy growth. Fertilizing can also aid in encouraging flowering. Mountain thistle is suitable for anyone with outdoor spaces like a garden or patio and does not demand extensive gardening experience. It may need more attention if grown indoors.

— PlantMom
CARE GUIDE

How to keep Acanthus Montanus.

Light

Mountain thistle flourishes with ample sunlight yet is robust enough to endure lower light conditions. Coming from open habitats, this plant is adapted to abundant sun. For healthy development, it needs steady sun exposure. Both insufficient and excessive sunlight can negatively affect its vitality.

Water

Mountain thistle thrives in rocky terrain and is drought-tolerant. It needs moderate watering each week and well-draining soil to avoid waterlogging. Maintaining consistent moisture during the growing season helps support its lush foliage and vibrant flowers, similar to its natural environment in warmer climates.

Temperature

Mountain thistle comes from tropical areas, where the climate is usually warm and humid. Consequently, it is adapted to high heat and moisture. It does not tolerate sudden temperature changes and prefers a steady temperature, so avoiding temperature fluctuations indoors is important. It generally cannot endure cold and needs warmer conditions to grow. If the ambient temperature falls too low, the plant may stop growing or even die.

Fertilizer

Appropriate fertilization is essential for Mountain thistle's health and appearance. Fertilize Mountain thistle during the summer, repeating the treatment monthly throughout the season. Nutrients supply the energy for growth and help maintain the plant's parts. Fertilizing improves Mountain thistle's flower display, ensuring the best blooms.

Pruning

To ensure healthy growth and improved air circulation, prune mountain thistle from early to late spring by cutting back old stems. This trimming process helps maintain the plant’s shape and encourages fullness. Be sure to make cuts just above a node. It's important to use clean tools to prevent the spread of disease, which not only enhances the plant's appearance but also its overall vitality.

CHARACTERISTICS

Botanical profile.

Plant Type
Herb
Life Cycle
Perennial
Genus
Acanthus
Family
Acanthaceae
Hardiness Zone
9-11
Mature Height
1.22 m to 1.83 m
Mature Spread
61 cm to 91 cm
Leaf Color
Green
Leaf Type
Evergreen
Flower Color
Purple, White
Flower Size
3.05 cm to 5.08 cm
Bloom Time
Summer, Early fall, Mid fall
Planting Time
Spring, Summer, Autumn
Harvest Time
Fall
Native Area
Benin, Angola, Sierra Leone, Equatorial Guinea, Cameroon, Burundi, Mozambique, Chad, Zambia, Nigeria, Congo, Gabon, Congo (DRC), Central African Republic, Zimbabwe
ALSO KNOWN AS

Other names.

en Mountain thistle
FREQUENTLY ASKED

Reader questions.

How should I water my Mountain thistle plant?

When watering the Mountain thistle, it is important to use filtered water at room temperature. Tap water can contain harmful particles for the plant, so it's best to avoid using it. Additionally, the water should be at room temperature or slightly warmer because the Mountain thistle thrives in warm environments and cold water can shock it. Instead of overhead watering, apply the filtered room temperature water directly to the soil until it is completely soaked. This method benefits the plant as it helps moisten the roots and allows them to spread and collect necessary nutrients.

What kind of sunlight does Mountain thistle need?

Mountain thistle is a plant that thrives in full sun and requires at least six hours of sunlight to maintain healthy leaves, roots, and blooms. While most perennials also need six hours of sunlight per day, plants such as the Orange Daylily or Giant Coreopsis can survive on a minimum of three hours of sun. However, it's important to note that these flowering plants may not flourish as well as they would in sunnier conditions.

What should I do if I give my Mountain thistle plant too much or too little water?

Taking care of your Mountain thistle requires you to be cautious with watering. While both overwatering and underwatering can harm the plant, overwatering is a more common issue. Too much water can cause the stems and leaves to wilt and turn yellow. It can also lead to serious diseases like root rot, mold, and mildew, which can be fatal for the plant. On the other hand, underwatering is less likely to occur since the Mountain thistle has decent drought tolerance. However, it is still possible and can cause the leaves to become brittle and brown. It is essential to recognize the signs of overwatering early on. Diseases like root rot may be irreversible if not addressed promptly. If you notice signs of overwatering, reduce your watering schedule and check the soil's drainage. If the soil drains poorly, replace it with a loose, well-draining potting mix. Conversely, if you notice signs of underwatering, increase your watering frequency until the signs improve.

Can the sun harm Mountain thistle? How can we shield Mountain thistle from the sun and excessive heat?

In warm climates, some Perennial Flowering Plants may struggle with excessive heat and suffer from sun damage. They can wilt, dry out, or even experience growth problems if they are consistently exposed to the intense afternoon sun. However, not all plants require protection from the light afternoon sun. For those that are harmed by intense afternoon exposure, it is recommended to provide them with some shade in warmer climates. Gardeners can achieve this by planting these plants in areas that do not receive direct heat during the afternoon, such as under trees or behind bushes.

How frequently should I water my Mountain thistle plant?

If your Mountain thistle is in a pot, the most accurate way to determine if it needs water is to check the moisture level of the soil by sticking your finger into it. If the top two to three inches of soil feel dry, then it's time to water the plant. For those who have planted the Mountain thistle outdoors in the ground, you can use a similar method to test the soil moisture. Once again, if the first few inches of soil have dried out, it's time to give the plant some water. During the spring and early fall seasons, this method will usually indicate a need to water the plant once a week. However, during extremely hot weather, you might need to water it twice or even more times per week. That being said, mature and well-established Mountain thistle plants have shown an impressive ability to endure periods of drought.

Should I keep the Mountain thistle plant away from the sun?

Certain perennial plants require ample sunlight to reach their maximum bloom. However, in warmer climates, some of these plants actually benefit from less sun. For instance, individuals residing in hotter regions might find it beneficial to shade their flowering perennials during the intense afternoon sun, especially during summer months. Although many perennial flowering plants prefer partial shade in the hottest climates, there are exceptions. Take the Giant Coreopsis, for example, as it is not bothered by excessive sun exposure. These plants can flourish even when placed in the full sun during scorching weather.

How much water does my Mountain thistle plant need?

To water your Mountain thistle effectively, don't hold back on the amount of water you give. Make sure the top few inches of soil are dry before watering, and when you do water, make sure to thoroughly soak the soil. You should add enough water to cause excess water to drain out of the bottom of the pot. If no excess water is draining, you might not be giving enough water, but be careful not to let water accumulate in the soil. Poor drainage can also be a problem, so make sure the soil drains well. If the plant is outside, 1 inch of rain per week should be enough.

What happens if Mountain thistle doesn't get enough sunlight?

If your Mountain thistle isn't getting enough sunlight, you will see signs of insufficient conditions in your plants. They will not produce as many blooms as they would with full sun exposure. Some plants may have dry spots on their leaves, but they will still bloom in limited sunlight. However, the flowers will be smaller and less full.

What is the best way to water my Mountain thistle as it grows?

The water needs of the Mountain thistle can change depending on its growth stages. During the first few years or after transplanting, it requires more water than usual because it focuses on sprouting new roots for future growth. These roots need more moisture in the early stages. As the plant matures, it requires less water. Additionally, during the bloom period, the Mountain thistle may need more water due to the significant amount of moisture required for flower development.

Does Mountain thistle require specific sunlight care at different growth stages?

Mountain thistle is a wonderful flower for gardens and thrives with at least six hours of sunlight daily. Occasionally, to keep the flowers fresh for longer periods, it helps to provide them with some shade during the hottest parts of the day. When the Mountain thistle is young, it is important to ensure that they receive enough sunlight without being exposed to intense afternoon heat. However, once the plant is fully mature, it will benefit from ample sun to support its growth.

How do I water my Mountain thistle at different times of the year?

The Mountain thistle will require the most water during the hottest months of the year, particularly during the height of summer. Depending on how quickly the soil dries out, you may need to water this plant more than once per week. However, during the winter, the plant will go into a dormant phase and will need significantly less water. In fact, you may not need to water it at all during winter months. If you choose to water during the winter, make sure to do so no more than once per month. Excessive watering during this time can increase the risk of disease for the Mountain thistle.

How much light does Mountain thistle need to make food?

Mountain thistle requires at least six hours of light to optimize their photosynthesis. The sun is necessary for the growth of their foliage and blooms. On the other hand, perennial flowering plants such as the Giant Coreopsis may require between eight and twelve hours of full sun daily to sustain their sizable flowers and healthy foliage.

PLATES
Acanthus montanus leaf
PLATE 01 · leaf
Acanthus montanus leaf
PLATE 02 · leaf
Acanthus montanus flower
PLATE 03 · flower
Acanthus montanus flower
PLATE 04 · flower
Acanthus montanus fruit
PLATE 05 · fruit
Acanthus montanus fruit
PLATE 06 · fruit
ALSO IN THE LIBRARY

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