Daffodils bloom from early to mid-spring, growing from a perennial bulb structure that spends the summer and winter months in a dormant state. This short growing season leaves the garden bed open to weed invasion for the rest of the year. Controlling the weeds without disturbing the bulbs is vital for the health of the daffodil plants. Weeds harbour insects and pests and compete with the daffodil bulbs for water and nutrients.
Treat the bed before planting the bulbs or as late as two weeks after planting, using a pre-emergent herbicide containing oryzalin or pendimethalin, per label directions. While these herbicides kill germinating weed seeds, they do not harm newly planted daffodil bulbs. Water in the herbicide and keep the bed moist.
Spread a 2- to 3-inch layer of mulch over the daffodil bed immediately after planting. Replenish the mulch layer in the spring when new growth begins. Mulch inhibits weed seed germination but doesn't prevent the daffodils from growing.
Pull weeds by hand as soon as you notice them, preventing them from rooting fully in the soil. Inspect the bed once or twice a week for new weeds, as young plants are easier to pull than established ones.
Plant annual flowers in the bed when the daffodils stop blooming. The flowers provide colour and shade the bed during the summer months, which prevents weeds from establishing in an empty bed.
Herbicides formulated for grasses can be used at any time in the daffodil bed to control perennial and annual grass weeds.
Do not use hay as a mulch, as it often contains weed seeds. Use bark or straw.