Why Is My Rhubarb Flowering? What Boise Gardeners Should Know...
If your rhubarb suddenly sends up a tall flower stalk in the spring, don't worry—you haven't done anything terribly wrong. What gardeners often call "bolting" is simply rhubarb entering its natural reproductive stage and producing a flower instead of putting all of its energy into growing those large, edible stalks we enjoy.
For gardeners in Boise and throughout the Treasure Valley, flowering rhubarb can be particularly noticeable because our growing season can quickly transition from cool spring weather to hot, dry summer conditions.
Why Does Rhubarb Bolt?
From the plant's perspective, flowering is perfectly normal. Rhubarb is a perennial plant, and producing flowers and seeds is simply part of its natural life cycle.
From the gardener's perspective, however, we'd much rather have the plant putting its energy into producing healthy stalks and strong roots for next year's growth.
Several factors can cause rhubarb to flower.
Heat and Water Stress
One of the biggest challenges for rhubarb in the Boise area is our summer heat. Rhubarb prefers cool growing conditions, and temperatures climbing into the 90s can put considerable stress on the plant.
Dry soil can add to that stress. Rhubarb needs consistent moisture, particularly during periods of warm weather. A plant that experiences repeated cycles of drying out and then being heavily watered may be more likely to become stressed and produce a flower stalk.
Keeping the soil evenly moist—but not waterlogged—is important. A layer of organic mulch around the plant can help conserve moisture and moderate soil temperatures.
Plant Age Can Make a Difference
Older, well-established rhubarb plants are generally more likely to flower than young plants. If your rhubarb has been growing in the same location for many years, flowering may simply be a sign that the plant needs to be rejuvenated.
Rhubarb crowns can benefit from being divided every four to five years. Dividing an overcrowded crown can help restore vigor and provide you with additional plants for other areas of the garden.
Variety Matters
Some rhubarb varieties are naturally more likely to produce flower stalks than others. Older, traditional varieties can be particularly prone to flowering, while some newer cultivars have been selected for better stalk production and reduced bolting.
If you purchased your rhubarb from a garden center such as ours, knowing the variety can be helpful when trying to understand its growing habits. If it was passed along from a friend or has been growing in your garden for many years, the exact variety may be unknown—and that's perfectly fine.
Keep Your Rhubarb Well Fed
Rhubarb is a heavy-growing perennial and benefits from good soil fertility. In the Boise area, adding compost or well-aged manure around established plants in early spring can help provide nutrients while improving our often-heavy clay soils
Avoid excessive fertilizer, however. The goal is steady, healthy growth rather than pushing the plant into producing excessive foliage.
What Should You Do When Rhubarb Flowers?
The good news is that bolting isn't a disaster.
As soon as you notice a flower stalk emerging from the center of the plant, cut it off at the base with a clean knife or pruners. Don't wait for the flowers to open and produce seeds.
The plant may send up another flower stalk, so check it periodically and remove any additional stalks that appear.
Removing the flower stalk redirects the plant's energy toward maintaining its leaves, roots and edible stalks rather than producing seeds.
Does Flowering Make Rhubarb Stalks Poisonous? No.
Flowering does not make the edible rhubarb stalks poisonous. The stalks remain safe to eat when harvested properly, whether or not the plant has produced a flower.
However, there is an important distinction: never eat rhubarb leaves. The large leafy portions contain high levels of oxalic acid and should not be consumed. Harvest and use only the stalks.
A Little Flowering Isn't a Reason to Give Up on Your Rhubarb
Rhubarb can be a long-lived and productive perennial in the Treasure Valley when given the right conditions. A plant may occasionally flower even when you are doing everything correctly.
For Boise gardeners, the best approach is to keep the plant healthy by providing consistent moisture, good soil, adequate nutrition and some protection from extreme summer heat. Remove flower stalks when they appear, and your rhubarb should continue putting its energy where you want it—into healthy roots and those delicious stalks.
And remember, a flowering rhubarb plant isn't necessarily a problem. It's simply the plant doing what plants naturally do: trying to reproduce itself.
Happy gardening,
The Home & Garden Store - Boise, Idaho
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