Getting it to bloom

Why won't my Black Spruce bloom? (and how to make it flower)

Also called Black Spruce, Swamp Spruce, Bog Spruce (Picea mariana).

More about black spruce

About Black Spruce

Picea mariana · also called Black Spruce, Swamp Spruce · flowering

Black Spruce is one of the hardiest conifers in North America, dominating cold boreal forests and sphagnum bogs from Alaska to Newfoundland. It tolerates waterlogged, nutrient-poor, highly acidic soils where few other trees survive. Slow-growing and compact, it suits cold-climate gardens, rain gardens, and naturalistic bog plantings.

Plant type: flowering

Watch for — Spruce Budworm: Choristoneura fumiferana is the most destructive pest of Black Spruce, capable of killing stressed trees during outbreak years. Maintain optimal growing conditions to reduce susceptibility. Biological insecticides (Btk) can protect young trees.

The reasons black spruce isn't blooming

Almost every non-blooming black spruce 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 black spruce 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 black spruce to flower

Maximise sun. Give black spruce 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 black spruce and get the feeding right with the black spruce 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

Black Spruce 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 black spruce care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Black Spruce blooming — frequently asked questions

Why won't my black spruce flower?

Black Spruce 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 black spruce bloom?

Give black spruce 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 black spruce normally bloom?