Many do this incorrectly. Here’s the right way to grow lilac from cuttings.

9. Watering, Ventilation, and Daily Care During Rooting
Water the cuttings lightly to keep the soil consistently moist but not soggy. Too much water can lead to rot, while too little will cause the cuttings to dry out. Monitor the moisture level regularly, adjusting as needed based on environmental conditions.
Ventilate the cuttings daily by briefly removing the plastic cover to allow fresh air to circulate. This will help prevent mold and mildew from developing. Keep an eye on the cuttings for any signs of disease or wilting, addressing any issues promptly.
10. How to Check for Roots and Pot Up Without Setbacks
After about 4 to 6 weeks, check for root development by gently tugging on the cuttings. If you feel resistance, roots have likely formed. Carefully remove the cuttings from the soil, being cautious not to damage the delicate roots.
Transplant the rooted cuttings into individual pots filled with a high-quality potting mix. Water the newly potted plants and place them in a bright, sheltered location to acclimate. Avoid direct sunlight until the plants are well established.
11. Hardening Off and Planting Out for Long-Term Success
Once the lilac cuttings have developed a robust root system and are actively growing, begin the hardening-off process. Gradually expose the plants to outdoor conditions over a week or two, increasing their time outside each day.
Choose a planting site with well-draining soil and full sun, spacing the lilacs at least 5 feet apart to allow for their mature size. Plant the lilacs at the same depth as they were in their pots, and water them thoroughly to settle the soil. With proper care and attention, your lilacs will thrive and provide beauty and fragrance for years to come.