Getting it to bloom

Why won't my Prairie Dock bloom? (and how to make it flower)

Also called Prairie dock, Prairie rosinweed, Basal-leaved rosinweed (Silphium terebinthinaceum).

More about prairie dock

About Prairie Dock

Silphium terebinthinaceum · also called Prairie dock, Prairie rosinweed · flowering

Silphium terebinthinaceum is a bold North American prairie native distinguished by enormous sandpaper-rough basal leaves (up to 60 cm / 24 in long) that remain near the ground while leafless, wiry flowering stems rise dramatically to 2-3 m (6-10 ft) in midsummer, bearing clusters of small yellow daisy flowers. Like all Silphium species it develops a deep taproot and is strikingly drought-tolerant but resents disturbance once established. The most important care fact is to site it where the impressive foliage can be appreciated and where its height will not shade shorter neighbours. Silphium species are not listed by the ASPCA as toxic to cats or dogs.

Plant type: flowering

Watch for — Wind rock and stem collapse: The tall, slender flowering scapes can be toppled by strong winds, especially in exposed sites or on overly fertile soils. Site in a sheltered position or use discreet staking; avoid rich soil that promotes weak, oversized stems.

The reasons prairie dock isn't blooming

Almost every non-blooming prairie dock 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 prairie dock 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 prairie dock to flower

Maximise sun. Give prairie dock 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 prairie dock and get the feeding right with the prairie dock 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

Prairie Dock 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 prairie dock care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Prairie Dock blooming — frequently asked questions

Why won't my prairie dock flower?

Prairie Dock 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 prairie dock bloom?

Give prairie dock 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 prairie dock normally bloom?