Description
Cirsium calcareum, also known as the limestone thistle, is a species of thistle plant belonging to the family Asteraceae. This perennial plant is native to North America, specifically found in Arizona, New Mexico, and Texas. It was first described as a species by Marcus Eugene Jones, an American botanist, in 1902.
General Appearance
The limestone thistle can grow up to 3.3 feet (1 meter) tall, with a basal rosette that can span up to 2.7 feet (0.8 meters) in width. The rosette leaves are deeply lobed and have spiny margins. The stem of the plant is also covered with spines and produces one or multiple heads of flowers.
Common Names
Apart from limestone thistle, Cirsium calcareum is also known by other common names such as calcareous thistle, Jones' thistle, and mountain thistle.
Uses
Some Native American tribes used the roots of the limestone thistle for medicinal purposes such as treating coughs, bronchitis, and digestive disorders. The plant is also attractive to pollinators, specifically bees and butterflies, and can be used in gardens as an ornamental plant. However, it should be noted that the plant is considered endangered in some areas due to habitat loss and degradation.
Light Requirements
Cirsium calcareum, commonly known as the limestone thistle, requires at least six hours of full sun per day. It can, however, tolerate some shade during the afternoon. Plants grown in full sun tend to be shorter and more compact with a higher number of flower heads, while those in partial shade tend to be taller with fewer flower heads.
Temperature Requirements
Cirsium calcareum thrives in a wide range of temperature conditions. It can tolerate both extreme heat and cold, with an optimal temperature range of 18-24°C (65-75°F). However, it can survive temperatures as low as -30°C (-22°F) and as high as 40°C (104°F).
Soil Requirements
Cirsium calcareum prefers well-draining, sandy or loamy soil that is slightly acidic to neutral (pH 6-7). It can grow in a wide range of soil types, including rocky or gravelly soils. The limestone thistle is highly adapted to growing in soils with low fertility and can withstand prolonged dry periods. However, it does not tolerate waterlogged conditions, so good drainage is crucial.
Cultivation of Cirsium calcareum
Cirsium calcareum grows best in full to partial sun and well-drained soil that is rich in organic matter. It thrives in areas with moderate to high rainfall and where the temperature doesn't drop below 20°F.
It is recommended to plant Cirsium calcareum in the spring or fall. When planting, ensure that there is enough spacing between each plant, about 12 to 24 inches apart. Dig a hole twice as wide as the root ball and add compost to the soil to boost the nutrients the plant will absorb. After planting, cover the soil with a layer of mulch to retain moisture and regulate soil temperature.
Watering Needs of Cirsium calcareum
Cirsium calcareum is moderately drought-tolerant but requires consistent moisture in the soil. Water the plant deeply once a week, making sure that the soil is moist 6-8 inches deep. During dry weather, increase watering frequency to ensure that the plant doesn't dry up or wilt. It's better to water in the morning or evening when the weather is cooler to minimize water loss through evaporation.
Fertilization of Cirsium calcareum
Cirsium calcareum doesn't require a lot of fertilizer. However, it responds well when fed with a balanced fertilizer like an all-purpose fertilizer or one that's high in nitrogen. During the growing season, apply the fertilizer at half-strength to avoid burning the roots. Follow the instructions on the packaging to determine the amount of fertilizer to use. Fertilize the plant every four to six weeks for the best results.
Pruning of Cirsium calcareum
Cirsium calcareum doesn't require much pruning. However, deadheading the plant after it blooms will encourage it to produce more flowers. Cut the stem below the faded flower but above the first set of leaves. If the plant gets too tall and spindly, you can pinch back the top growth to promote bushiness and lateral growth. You can also cut back the entire plant by one-third in early spring to stimulate new growth.
Propagation of Cirsium calcareum
Cirsium calcareum can be propagated using seeds or by division. Both methods have their advantages and disadvantages and the choice of the method depends on the grower's preferences and resources.
Propagation by Seeds
Propagation from seeds is a common and relatively easy method of propagating Cirsium calcareum. The seeds should be sown in pots or trays filled with a well-draining soil mix. The seeds should be kept moist and warm until they germinate. Once the seedlings have grown big enough, they can be transplanted to individual pots or directly in the garden.
Seeds can be harvested from mature plants in late summer or early fall. The seeds should be stored in an airtight container in a cool and dry place until the next growing season.
Propagation by Division
Propagation by division is another method of propagating Cirsium calcareum. This method involves dividing the plant into smaller sections and replanting them. This method is best done in the early spring before new growth begins.
The plant should be carefully dug up and the roots should be gently separated into smaller sections. Each section should have roots and at least one shoot. The new plants should be planted immediately in a well-draining soil mix and watered well.
Propagation by division is a good method of propagating if the grower wants to increase the number of plants quickly. However, it may take longer for the new plants to flower than those propagated from seed.
Disease and Pest Management for Cirsium calcareum (M.E. Jones) Woot. & Standl.
Cirsium calcareum (M.E. Jones) Woot. & Standl. is a perennial plant that grows well in sunny and well-drained areas. However, like any plant, it can be susceptible to diseases and pests.
Common Diseases
One of the common diseases that affect Cirsium calcareum is powdery mildew. Powdery mildew is identified by a grey or white powdery substance that appears on the leaves, stems, and flowers of the plant. To manage powdery mildew on Cirsium calcareum, remove infected leaves and ensure that the plant gets plenty of sunlight and airflow. Additionally, apply a fungicide to the plant to control the disease.
Another disease that affects Cirsium calcareum is rust. Rust is identified by orange, yellow, or brown spots that appear on the leaves, stems, and flowers. To manage rust on Cirsium calcareum, remove infected leaves, and ensure that the plant gets plenty of sunlight and airflow. Additionally, apply a fungicide to the plant to control the disease.
Common Pests
One of the common pests that affect Cirsium calcareum is aphids. Aphids are small insects that suck the sap from the plant, causing stunted growth and yellowing leaves. To manage aphids on Cirsium calcareum, spray the plant with a hose to remove the insects, or apply an insecticide carefully, following the manufacturer's instructions.
Another pest that affects Cirsium calcareum is spider mites. Spider mites are small mites that feed on the plant's sap and can cause discoloration and deformation of the leaves. To manage spider mites on Cirsium calcareum, apply an insecticide that targets spider mites. Additionally, you can introduce natural predators such as ladybugs to control the mites.
In conclusion, by managing diseases and pests that affect Cirsium calcareum, you can ensure that the plant thrives and remains healthy.
