The Q&A Archives: Fertilizing Blue Skies Lilac

Question: Our nursery says that we should use 1 lb per each inch of trunk per month starting Aug through Jan (start of bloom). This is required because the Lilac wants acid soil if it is to have blooms.

Answer: I'm concerned that your nursery is recommending too much fertilizer! One pound per month is excessive for any tree or shrub and may actually burn the roots and cause the death of your plant.

Lilacs respond vigorously to regular, light applications of fertilizer. The amounts you apply will depend upon the type of fertilizer you purchase. Recommendations are listed on the fertilizer label - don't feed more than the label suggests or you could burn your plant. Here are some basic guidelines: Fertilize established (second year and after) lilacs in early spring (March or early April), with a 5-10-5, 5-10-10, 10-10-10 or 20-20-20 formula. Apply before growth has begun. Broadcast directly on soil over root zone. Slow release or organic fertilizers can be applied a little later in the season when soil has warmed. Avoid high nitrogen fertilizers, since you will get foliage at the expense of flowers, and you may encourage some diseases. Lilacs prefer somewhat alkaline soils. If the pH is below 6.0, dolomite lime may be gently worked into soil.

Blooming is mostly determined by variety of lilac, and the amount of sunshine it receives (all day sunshine is best). Most require a pronounced winter chill in order to bloom profusely; 'Blue Skies' is one of the Descanso Hybrids which were developed for mild winter areas such as yours. It will bloom without a pronouced winter chill and it will produce more and more blooms as it matures. Lilacs are relatively adaptable and will grow in mildly acidic, neutral, or slightly alkaline soils. If your soil pH measures between 6.0 and 7.5, your lilac should be happy.

Best wishes with your lilac!

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