Blue Hyacinth Petals Turning Brown

Pest Infestation

• Although other pests may infest your hyacinths, the type most likely to cause petal browning involves a type of minuscule insect known as thrips. Flower thrips may damage numerous types of plants, including flowering bulbs, although they prefer grasses and plants with pale blossoms. These small insects pierce the petals and feed on the sap, damaging the blossoms. This type of feeding causes the colorful hyacinth petals to turn brown and curl up. Some blossoms may stop opening while they are still in their bud state.

Fungal Disease

• Petal blight may also cause hyacinth petals to turn brown, although this condition tends to affect later blossoms more heavily than the early spring flowers. This condition occurs most frequently during warm, humid weather. Muggy, rainy days usually precipitate an incident of petal blight. A variety of fungi, including botrytis blight and lily mosaic, can cause this disorder that may also affect the leaves. Infected blossoms develop brownish spots that spread and merge into large areas of damage. Left untreated, some cases of petal blight may damage entire plants.

Prevention

• Proper planting and care helps promote the overall health of your hyacinths, helping them withstand adverse conditions, such as prolonged humidity and pests. Grow your hyacinths in sites that contain well-drained soil and provide full sunlight to light shade. Keep the soil near the roots slightly moist, allowing the surface to dry between watering sessions. Trim off any brown blossoms or leaves as they appear. Fertilize your hyacinths when they begin growing in the spring, using a fertilizer for blossoming bulb plants.

Treatment

• Remove weeds and grasses around your hyacinth plants to discourage the migration of thrips. Use a pesticide labeled for the treatment of thrips, such as acetamiprid, cyfluthrin or kinoprene. Treat fungus conditions in hyacinths by cutting off dead blossoms and applying a fungicide according to the label instructions. Remove any dead vegetation from the soil around the plants.