Getting it to bloom

Why won't my Japanese Tree Lilac bloom? (and how to make it flower)

Also called Japanese tree lilac (Syringa reticulata).

More about japanese tree lilac

About Japanese Tree Lilac

Syringa reticulata · also called Japanese tree lilac · flowering

Japanese tree lilac is a small, single-stemmed flowering tree rather than a shrub, topping out far larger than common lilac. In early summer, after most lilacs finish, it bears huge creamy-white, fragrant flower clusters above glossy foliage, set off by attractive cherry-like reddish-brown bark. Tough, hardy, and pollution-tolerant, it is a popular street and specimen tree.

Plant type: flowering

Watch for — Heavy spent-flower set: It flowers prolifically and the browning clusters and seed heads can look untidy and reduce next year's bloom. Deadheading large trees is impractical, so expect some biennial flowering.

The reasons japanese tree lilac isn't blooming

Almost every non-blooming japanese tree lilac traces back to one of these, roughly in order of how common they are:

Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
The plant has not been deadheaded, so it stops flowering once it sets seed.
Irregular watering — drought or waterlogging at the budding stage makes buds abort.
It is still too young or was checked by a transplant and is rebuilding before flowering.

Feeding japanese tree lilac a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.

The fix — how to get japanese tree lilac to flower

Maximise sun. Give japanese tree lilac the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.

Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for japanese tree lilac and get the feeding right with the japanese tree lilac fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.

Bloom season and what to expect

Japanese Tree Lilac flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.

Post-bloom care so it flowers again

Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.

For everything else this plant needs day to day, see the full japanese tree lilac care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Japanese Tree Lilac blooming — frequently asked questions

Why won't my japanese tree lilac flower?

Japanese Tree Lilac blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.

How do I make japanese tree lilac bloom?

Give japanese tree lilac the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.

When does japanese tree lilac normally bloom?