Cosmos Mandarin Seedling Tray

For best results with Mandarin, plant one rooted plug per gallon container. Use well-drained soil in full or partial sun with light feed (100-175 ppm N), a pH of 5.8-6.2, and an EC (via 2:1 extraction) of 1.2-1.5 mS/cm. Provide temperatures of 60-64 daytime and 57-60 nighttime. Don't pinch, but use daminozide or chlormequat as needed. Watch for aphids, thrips, fusarium wilt, and leaf spot. 

Pinnate orange flowers bloom from mid-spring until frost.

This plant doesn't require pinching.

Space containers for adequate airflow and sunlight penetration around the base and foliage of each plant. We recommend spacing 4-inch, gallon, or 10-inch containers 12-18" on center for good ventilation and disease prevention. Adjust spacing in your commercial greenhouse as needed for your plants.

Once the plant establishes roots, you may apply daminozide or chlormequat chloride as needed to control height. Drought stress and negative DIF are also effective height control methods. 

Watch for aphids and thrips as part of your Integrated Pest Management plan.

Aphids are small, soft-bodied insects that cause damage by sucking sap from plant tissue. They reproduce quickly and are particularly attracted to young growth. Curling and yellowed leaves, stunted growth, and stickiness on leaves are signs of an infestation. These insects also spread diseases and reproduce rapidly. Use biological controls or horticultural oils to discourage and kill aphids.

Thrips are tiny insects that eat plant tissue and can transmit viruses. Watch for silvery-white streaks or black spots on foliage and distorted growth. Use natural predators (like predatory mites), insecticidal soap, neem oil, and sticky traps to control infestations and prevent spread.

Watch for signs of fusarium wilt and leaf spot. Take basic preventative measures in your greenhouse as part of Integrated Pest Management, including watering at the base of each plant, allowing the soil to dry between waterings, using proper fertilizer and light, maintaining a clean and debris-free environment, and sanitizing equipment. Provide adequate spacing and good airflow for seedling plugs.

Fusarium Wilt is a fungal disease that causes leaves to wilt and turn yellow. Use clean growing media and sterilize pots, trays, and tools before transplanting seedling plugs. Inspect plants regularly for signs of disease, checking roots and stems for discoloration and wilting. Remove and destroy infected plants to prevent the spread of fusarium fungus.

Bacterial Leaf Spot results from a bacterial pathogen and causes water-soaked yellow or brown lesions on foliage. These may merge and cause leaves to turn yellow and drop. Prevent bacterial leaf spot by practicing sanitation and hygiene, watering at the base of each plant, and space plants for adequate circulation and light penetration. At the first signs of infection, remove the affected leaves and treat the remaining plants with a copper-based fungicide like hydroxide, sulfate, oxychloride, or octanoate. Use fungicides carefully according to the label's instructions, and be aware that applying copper-based fungicides at high rates or during hot, dry weather can lead to phytotoxicity.

We recommend planting one seedling plug per 4-inch or 6-inch container. Use well-drained soil and completely bury the ellepot in the center of the container.