Hypericum japonicum, known as matted St. John's-wort, is an annual herbaceous flowering plant in the St. John's wort family Hypericaceae, in Hypericum sect. Trigynobrathys.
Matted St. John's-wort is fairly disease-resistant and generally not prone to illness. Still, it can be affected by pests and diseases present in its environment, though these problems are typically mild. As for care, the plant has moderate maintenance needs. It should be pruned regularly to preserve an attractive appearance and support healthy growth. Applying fertilizer can also encourage it to flower. Matted St. John's-wort is well suited to people with outdoor spaces like a garden or patio and does not demand a great deal of gardening experience. It may need extra attention if grown indoors.
How to keep Hypericum Japonicum.
Light
Matted St. John's-wort does best in places where the sun shines for much of the day, though it can adapt to areas where sunlight is occasionally obscured by clouds. Originating in a sun-rich environment, it prospers through all stages of growth as long as it receives ample light. However, too much or too little light can impair its vigorous growth.
Water
Matted St. John's-wort flourishes in wet environments, thriving in humid conditions and tolerating high moisture levels. To stay healthy, it needs to be watered weekly. This herbaceous perennial grows best in moist soils, making it perfect for container gardening, where you can easily manage water levels.
Temperature
Matted St. John's-wort is fairly adaptable to temperature, able to endure higher heat and greater temperature fluctuations. During hot periods, attention should be paid to watering and providing suitable shade to avoid sunburn. Conversely, its tolerance of low temperatures is relatively limited. While it can handle some cold, very low temperatures can cause frost damage.
Fertilizer
Matted St. John's-wort does well with regular, weak applications of fertilizer to encourage healthy leaf growth. Apply fertilizer to Matted St. John's-wort roughly once a month during the summer months. Nitrogen is important for foliage, and adding nitrogen-rich sources helps Matted St. John's-wort thrive.
Pruning
Matted St. John's-wort thrives with proper spring pruning, which enhances both its growth and blooms. To encourage new growth, trim the old stems regularly. Regular thinning helps prevent overcrowding and reduces the risk of disease. For the best results, use clean, sharp tools, which will also promote a compact and robust form.
Botanical profile.
- Plant Type
- Herb
- Life Cycle
- Annual
- Genus
- Hypericum
- Family
- Hypericaceae
- Hardiness Zone
- 7-10
- Mature Height
- 2 cm to 5 cm
- Mature Spread
- 15 cm
- Leaf Color
- Green
- Leaf Type
- Semi-evergreen
- Flower Color
- Yellow
- Flower Size
- 0.51 cm to 0.76 cm
- Bloom Time
- Summer, Early fall, Mid fall
- Planting Time
- Spring
- Harvest Time
- Late summer, Fall, Early winter
- Native Area
- Nepal, Sri Lanka, India, Malaysia, Philippines, Madagascar, Bangladesh, Laos, New Zealand, China, Indonesia, Cambodia, Vietnam, Myanmar, Japan, Bhutan, South Korea, Thailand
Other names.
Reader questions.
How should I water my Matted St. John's-wort plant?
To water Matted St. John's-wort, there are several options you can use: a garden hose with a spray nozzle, a watering can, or any other common watering tool. This plant is not too particular about its water source and can survive on rainwater, tap water, or filtered water. However, it is recommended not to water this plant from overhead as it can harm the leaves and flowers and potentially promote disease. Instead, a drip irrigation system is often the best method for watering. This system applies water evenly and directly to the soil, which works well for Matted St. John's-wort. If you have a container-grown plant, you can use the same approach but with different tools like a cup, watering can, or tap water to apply water directly to the soil.
What are the sunlight requirements for Matted St. John's-wort?
Matted St. John's-wort thrives best in full sun conditions, requiring more than 6 hours of direct sunlight daily. It can also adapt to partial sun, with about 3-6 hours of sunlight. This plant, originating from environments rich in sunlight, flourishes during all growth stages provided ample light is available. However, too much or too little sunlight can negatively affect its growth. It's important to watch how sunlight moves through your garden to choose spots that offer a perfect balance for your plants, ensuring their health and happiness.
What should I do if I give too much or too little water to my Matted St. John's-wort?
If you notice that your Matted St. John's-wort lacks moisture, the solution is simple - water it more regularly. However, overwatering can be a serious issue if not caught early. When your Matted St. John's-wort is overwatered, it can get sick and eventually die. To prevent this, choose a good location for it to grow, with ample sunlight and proper drainage. If you overwater a potted Matted St. John's-wort, you may need to transfer it to a new pot with better drainage and loose soil.
How can I provide adequate lighting for Matted St. John's-wort indoors?
For Matted St. John's-wort plants grown indoors, where natural sunlight may be insufficient, especially during winter or in less sunny spaces, artificial lighting is a vital alternative. Use 30-50W/sq ft of artificial light for full sun plants, 20-30W/sq ft for partial sun plants, and 10-20W/sq ft for full shade plants. LED lights are a popular choice because they can provide specific wavelengths needed by plants. Place the light source 12-36 inches above the plant to mimic natural sunlight and keep it on for 8-12 hours per day, mimicking natural daylight hours.
How frequently should I water my Matted St. John's-wort?
To keep your Matted St. John's-wort healthy, it's important to water it regularly. In the spring, watering once a week should be sufficient. However, as the weather gets warmer, you may need to increase the frequency to two or three times per week. It's important not to go overboard with watering though, as too much can harm the plant. Regardless of how often you water, make sure the soil remains moist but not saturated. Watering a potted Matted St. John's-wort is a bit different. Due to the faster drying out of soil in pots, you'll likely need to water the plant a few times per week, compared to just once per week for one planted directly in the ground.
What symptoms indicate light deficiency in Matted St. John's-wort?
Symptoms of light deficiency in Matted St. John's-wort include smaller new leaves than the previous ones, leggy or sparse growth due to longer spaces between leaves or stems, faster leaf drop to conserve resources, slower or halted growth as the plant enters survival mode, and paler new leaves indicating a lack of chlorophyll and essential nutrients. These symptoms suggest the need to increase the light exposure for the plant's health and well-being.
How much water does my Matted St. John's-wort plant require?
There are a few ways to determine how much water to give your Matted St. John's-wort plant. One method is to feel the soil and water until the top six inches are moist. Another option is to use a set amount of water, like two gallons per week, considering factors like temperature and soil moisture. However, be careful not to overwater if your plant needs less. When growing in a container, check the soil moisture by sticking your finger in or look for excess water draining from the pot.
What are the effects of too much sunlight on Matted St. John's-wort?
Excessive sunlight can lead to several problems for Matted St. John's-wort, including chlorosis (leaves losing their green color and turning yellow), sunscald (pale, bleached, or necrotic areas on leaves or stems), leaf curling (a defense mechanism to minimize water loss), wilting (loss of turgor pressure), and leaf scorching (brown, dry, and crispy leaf edges). These conditions affect the plant's ability to photosynthesize and its overall health, indicating a need for moderated light exposure.
How do I know if I am giving enough water to my Matted St. John's-wort plant?
Avoiding overwatering your Matted St. John's-wort can be tricky. While these plants need to be watered regularly because of their deep roots, they are very susceptible to root rot and browning from too much water. Underwatering is not a big concern as these plants can survive for some time without watering. But if you wait too long, the plant will start to wilt and the leaves may become dry.
How can I optimize sunlight exposure for Matted St. John's-wort?
To optimize sunlight exposure for Matted St. John's-wort, gradually move the plants to sunnier locations each week, ensuring they receive at least 6 hours of direct sunlight daily. For indoor plants, consider using artificial light if they are large or not easily movable. Outdoor plants should be moved to the best spot for sunlight gradually to avoid sunburn. Reducing obstructions, such as pruning tree branches, can also help. Transplant smaller plants during their dormant period to locations with ample sunlight and good drainage for the best growth outcomes.
How do I water my Matted St. John's-wort during the different seasons?
As the seasons change, the water requirements for your Matted St. John's-wort will change too. In the spring, water it once per week. When summer comes and the heat intensifies, you'll need to increase the watering frequency to about three times per week, especially for those growing in containers. Containers tend to dry out faster in warm weather. In the autumn, as the temperature cools down and the sun weakens, your Matted St. John's-wort will need slightly less water while still in bloom.
How do I water my Matted St. John's-wort as it grows?
Throughout the year, matted St. John's-wort goes through various growth stages, each requiring different amounts of water. When starting from a seed, it's important to provide extra water to help with germination and maintain consistent soil moisture. As the plant grows above the soil, the watering needs decrease slightly. Once fully mature, a regular watering schedule of approximately once per week is suitable. During flower development, slightly more water may be necessary to support the process.
