Who doesn’t love a good rhubarb pie? The thicker the rhubarb, the more delicious the filling. However, sometimes rhubarb stalks don’t grow as thick as you’d like.
Fret not! I have the best tips to ensure your homegrown rhubarb comes out plump and delicious:
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Table of contents
- 1. Grow Rhubarb in Rich, Organic Matter with Plenty of Compost
- 2. Place Rhubarb Plants in an Area with Temperatures Less than 90°F (32°C)
- 3. Cover Rhubarb Crowns with an Upturned, Large Pot to Force its Growth
- 4. Divide Rhubarb Crowns Every 4-5 Years to Prevent Overcrowding
- 5. Don’t Harvest Rhubarbs During its 1st Year of Growth
- 6. Plant Thick-Stemmed Rhubarb Varieties like Cherry Red or Mammoth Red
- 7. Remove Flower Stalks to Redirect Energy Back into Growing Thick Stems
1. Grow Rhubarb in Rich, Organic Matter with Plenty of Compost
It’s no secret that the more fertile the soil is, the more abundant the nutrients present for the plants. Rhubarb is no different, especially since it is a heavy feeder. A heavy feeder plant needs loads of nutrients to flourish exceptionally well in its growth. Kind of like how a marathon runner needs all those heavy carbs for energy.
So how do we increase a soil’s fertility? Easy peasy, just mix in any of the following into the ground:
Suppose you want to opt for synthetic fertilizers. In that case, it’s best to get one with high Phosphorus and Potassium content for your rhubarb. Avoid using a fertilizer high in Nitrogen, as this will cause your rhubarb to produce more foliage than you care for. The leaves are toxic, inedible, and aren’t even the reason you’re growing them in the first place.
Otherwise, an all-purpose fertilizer (Amazon link) is enough. However, make sure not to overfertilize the soil. With organic fertilizers like compost, it’s pretty hard to overfertilize. But with synthetic fertilizer, it takes just a little to offset your soil’s usability.
You’ll want to prepare the soil before planting your rhubarb crowns, making sure to mix the soil and fertilizer together well then place it where you plan to grow. Alternatively, place compost as mulch on top of the soil or around the plant yearly after it’s established.
2. Place Rhubarb Plants in an Area with Temperatures Less than 90°F (32°C)
The reasoning for this particular tip is simple: rhubarb develops better in cool climates. It thrives in areas where the ground freezes in winter, like in hardiness zones 3 – 8. This easily makes them an easy crop to grow in the northern parts of the country. By the time spring arrives, the plant emerges and is ready for harvest.
Additionally, rhubarb doesn’t need that much watering since the ground retains moisture over the cold season. But in warmer climates, you will need to water your rhubarb more frequently to ensure the foliage doesn’t shrivel from the dry heat. Planting rhubarb plants in shaded areas tend to help alleviate this particular issue.
Here’s how bad rhubarb hates the heat – some varieties will lose the vibrancy of their red stalk color as the temperature increases. Dramatic, I know. But really, the hotter it is, even just above 75°F, the higher the likelihood the plant becomes stressed and vulnerable to diseases. This is why it tends to be harder to grow rhubarb as a perennial in the southern areas. But that doesn’t mean it’s impossible! You just have to plant it as an annual. This means planting and harvesting it yearly as a cool-season crop before the summer peak arrives.
3. Cover Rhubarb Crowns with an Upturned, Large Pot to Force its Growth
This is a technique used to gain an early harvest of rhubarb, typically in January or February. Though some gardeners start as soon as November and December. The main idea in this technique is basically to cut off any source of light to the plant.
It usually involves two things:
- An item to cover the plant. You can use any item as long as it is wide enough to fit the plant as it grows, such as terracotta pots and bins. It also has to be opaque to prevent sunlight.
- Organic mulch like compost or aged manure.
Once the plant is covered, mulch is scattered on the bare soil around the hidden plant to provide nutrients for its growth. Some also choose to insulate the vessel’s exterior in colder areas with a row cover (Amazon link). It is said to accelerate the process. Honestly, it feels like they’re just torturing the rhubarb plant. Who says gardening can’t be hardcore?
After about 8 weeks or so, the rhubarb should be ready for harvest. Take note that this method is only advisable to use on mature rhubarb plants. Young rhubarb plants won’t have enough energy preserved in their growing stage to achieve this. Have pity, holy gardener.
Also, don’t repeat this method often to the same rhubarb plant. Otherwise, it won’t be strong enough to develop well afterward. In some cases, you’ll be forced to get rid of that particular rhubarb crown because it just stopped growing. It’s kind of like pushing your body to operate on nothing more than caffeine and adrenaline. At some point, the body is going to shut down. Give your rhubarb the rest it needs and let it grow.
4. Divide Rhubarb Crowns Every 4-5 Years to Prevent Overcrowding
This is kind of obvious, but it still needs to be said. The more crowded your rhubarb patch has grown, the less likely it will produce more thick stalks. This is where dividing the rhubarb crowns comes in handy.
Doing this in the 4th or 5th year is ideal. If you leave it as is for a decade, the patch will produce smaller stalks and leaves. It’s best to do this in early spring before the leaves have grown, preferably when it is still dormant. This gives the plant a chance to take root and develop for the rest of the growing season before winter comes.
You can also divide it in late fall, but it’s not ideal. If you do it in late fall just make sure to add a good layer of mulch to protect the rhubarb crowns over the winter season. Because despite it being a cool-season crop, it will still get damaged in hard freezes.
Here’s how you can divide your rhubarb:
- Dig a section of the rhubarb plant up. Try aiming for the most crowded areas.
- Using a sharp knife, divide the plant into individual crowns. Ensure that each crown has at least 1 prominent bud to grow from.
If you’re planting in the same spot, make sure to nourish the soil with compost first. The same patch likely has fewer nutrients after years of rhubarb growing there. So it may be better to plant the newly divided rhubarb crowns elsewhere.
5. Don’t Harvest Rhubarbs During its 1st Year of Growth
This is a crucial stage in developing rhubarb. You want it to become sturdy and robust enough with extensive roots. This is why it’s important to leave it as is during the 1st year.
You can only start to harvest rhubarb in the 2nd or 3rd year when the plant is well-established and mature to be continually harvested. A good tip for harvesting is to collect less than ⅓ of the plant’s stalks at the outer sections. I know it can be very tempting but try not to let your desires for a strawberry-rhubarb pie overcome the need for the plant to grow better. Trust me, waiting a year or two will be worth the plant’s plentiful and thicker future growth.
6. Plant Thick-Stemmed Rhubarb Varieties like Cherry Red or Mammoth Red
You can get everything right and care for your rhubarb plant extremely well annnnnnnnnnnnnnnnnnnnnd still end up with thin rhubarb stems. In that case, it probably has to do with the rhubarb variety you planted. Some varieties are prone to growing slender stalks naturally.
Here’s a few rhubarb varieties known to produce thick stalks:
- Cherry Red
- Mammoth Red
- Crimson Red Riverside Giant
7. Remove Flower Stalks to Redirect Energy Back into Growing Thick Stems
When your rhubarb starts producing flower stalks, this means the plant is suffering any one or a combination of these factors:
- Too much sunlight
- Decreased soil fertility
- Extreme temperature changes.
These flower stalks will then seed, which tends to produce rhubarb sprouts around the plant. Think of it as a last resort for the plant to survive – Like hey, if things go south, send up a flower! So the more flower stalks there are, the more significant the stresses are. In rare cases, it could be just a quirky trait of a particular rhubarb variety. There’s always an oddball somewhere.
So as soon as you see flower stalks appear, cut them off at the base of the plant and discard them. This way, the energy can be redirected to producing thicker stems rather than expending it on the rhubarb’s failsafe to survive. But it’s worth noting that you should also investigate the cause of your rhubarb’s stresses. Because even if you got rid of the flower stalks, the problem still exists.
Hopefully, with these tips, your rhubarb grows thick, strong, and glorious. Save me a rhubarb pie when you do harvest them. Happy planting!
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