A leafy, healthy forsythia that pushes out only a few flowers near the base is the classic sign of forsythia not blooming. The two causes are almost always the same. Either cold winter killed the flower buds, or someone pruned the shrub at the wrong time and cut off the buds. The plant itself is fine. Its bloom system just got knocked out before spring.
Look at where the few flowers showed up. On many shrubs the only blooms sit near the ground. Snow buried those lower branches all winter. That snow worked like a blanket and held the buds above freezing. The exposed top half lost its buds to the cold air. This same pattern explains a lilac not blooming well in a hard winter. Both shrubs send up green leaves no matter what. So a full leafy plant with no flowers fools a lot of gardeners every spring.
Forsythia and lilac both bloom on old wood. The flower buds form in summer, sit on last year's stems all winter, and open the next spring. So the buds you want this April were already on the plant last August. Anything that harms them between summer and spring takes your flowers with it. Penn State and South Dakota State extension both point to these two causes first. A shrub can stay green and still skip its whole show.
Cold is the cause you cannot control once the buds are set. Here is where flower bud hardiness matters most. Common forsythia keeps its leaf buds down to brutal lows. But its flower buds die below about -10°F (-23°C). The stems live, push leaves, and look fine. The flowers are simply gone. This is why a forsythia in a cold zone can look healthy for years. It still refuses to put on a real spring display.
Why does this matter so much for your shrub? Because the leaf buds and the flower buds have very different limits. Leaf buds are tough and shrug off deep cold. Flower buds give up far sooner. A single brutal cold snap can wipe out a whole year of bloom while the plant looks untouched. This is the quiet reason behind most cases of forsythia not blooming in northern gardens. The chart below shows how much that hardiness gap varies between common forsythia and tougher cultivars bred for the cold.
The other cause is the one you can fix right away. Pruning at the wrong time strips the buds before they get a chance. The buds form in summer. So any cut you make in fall, winter, or early spring removes next year's flowers. Prune within a few weeks after the blooms fade. That gives the shrub all summer to set fresh buds for next year. Wait too long and you trade a season of flowers for a tidy shape. This single timing mistake fools more gardeners than the cold ever does.
Check your pruning habit first, since timing is free to fix. Did you only cut right after flowering? If so and the shrub failed to flower anyway, cold is the likely culprit. In that case, swap to a bud-hardy cultivar. 'Meadowlark' holds its flower buds down to about -35°F (-37°C). It keeps blooming where common forsythia gives up. For lilac, pick a type rated for your zone. Then prune it on the same old-wood schedule, right after it finishes its spring flush. Get the timing right and the right cultivar, and your flowers will come back next year.
Read the full article: 10 Best Spring Blooming Shrubs Guide
