When the days grow shorter and the temperatures begin to drop, it's time to start thinking about how to care for Asiatic lilies in the fall (Lilium spp., called "Asiatic hybrids," USDA hardiness zones 4 to 8). Asiatic lilies are a beautiful addition to any garden, but they need special care to survive the colder months.
Deadheading Asiatic Lilies
Asiatic lilies bloom once a year, lasting for two to three weeks each bloom season. There are several varieties of Asiatic lilies, including 'Connecticut King' (yellow), 'Enchantment' (orange), 'Grand Prix' (red), 'Moulin Rouge' (red), 'Roma' (white) and 'Sterling Star' (white).
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It is important to deadhead Asiatic lilies in the fall. Deadheading refers to the removal of blooms from the plant once they have stopped flowering. This allows the plant to focus its energy on creating new blooms rather than wasting precious resources on developing seeds from the flowers. When you deadhead a plant, the energy that would have gone into helping the plant reproduce (either by creating seeds or fruits, depending on the plant) instead can help the plant produce more flowers instead.
To deadhead Asiatic lilies, use a clean and sterilized pair of shears or scissors, or just use your hands. Snip or snap the spent flower off the stem, taking care not to remove any leaves during the process. Your Asiatic lilies need that foliage to continue to photosynthesize throughout the winter.
Fertilizing Asiatic Lilies in Fall or Winter
Once you have deadheaded your Asiatic lilies, it's time to fertilize them. Asiatic lilies are heavy feeders, benefiting from a fertilizer high in nitrogen. You can choose either a granular fertilizer or a water-soluble fertilizer. If you select a granular fertilizer, apply it around the base of the plant and water it well. If you opt for a water-soluble fertilizer, mix it according to the manufacturer's instructions and apply it to the soil around the plant.
Keep lilies mulched to cool their roots. Viruses are one of the most pressing issues facing Asiatic lilies, and they are more likely to be an issue if roots are too warm or are sitting in waterlogged soil. Mulch will help with both of these problems.
Viruses of concern include Lily symptomless virus (LSV), Lily mottle virus (LMV) stripe, Cucumber mosaic virus (CMV), and Tulip breaking virus (streak disease). There are 11 viruses in total that can impact lilies, and many experts say you'll need to destroy and remove impacted plants to keep them from spreading. Continue to water Asiatic lilies in the cold weather if your region experiences rainfall less than an inch per week.
Fertilizing New Asiatic Lilies and Spring Care
If you are planting new Asiatic lilies, you will also need to fertilize them. Apply a quality high-potassium liquid fertilizer every two weeks from planting until six weeks after they flower.
Then, you'll need to cover the roots in a thin layer of compost each spring. You can follow that up with a 2-inch layer of mulch. Be sure to stake your tall lilies to offer support as they grow.
Asiatic Lily Pests and Disease
Asiatic lilies are also susceptible to several pests and diseases. To keep your plants healthy, it's essential to inspect them regularly for signs of problems. Common issues to look out for include aphids, spider mites and lily beetles. Aphids are small and pear-shaped. They look a bit like miniature common spiders, and you'll find them on the foliage of plants.
If you notice webbing on your lilies' foliage, closely inspect the plant for fast-moving bugs. These bugs, which are spider mites, may appear in a variety of colors, including black, silver or other colors. Their webbing is the easiest way to identify the mites. Lily beetles are red bugs that chew through the foliage of the lily plant. Check for lily beetles if you start seeing holes in your leaves or discoloration.
To prevent pests, use Neem oil once a week during the growing season. Neem oil is derived from the tree of the same name and has been used for centuries. Azadirachtin is the most active component in this oil. It is indicated for deterring and killing pests. Be sure to always follow label instructions with a pesticide, and keep it out of reach of kids and pets.