Blog – Green Thumb Luck

Rhubarb! A tangy and tart perennial that adds bright red stalks to my garden year after year. The perfect pairing with strawberries for arguably the most perfect fruit pie. My grandmother always kept cooked down rhubarb in her fridge for us to eat by the spoonful. I tried growing it so many times in my own gardens only to be defeated over and over again by the killer desert heat, or my totally un-green thumb. But once I moved from the super-dry, super-hot, I had to give it a go. To be completely transparent, my rhubarb is coming into it's second year after planting. The great garden gurus of Google U said not to harvest until year THREE, so I didn't dare to touch it. That said, my plants are happy and healthy and this spring, I might take a stalk or two from each plant and BAKE A PIE!!!! However, even though I haven't had a bite, I'm still going to share my tips because I am pretty sure we will have a good harvest and I am planting many more plants this spring. There couldn't be a better time to share how to grow rhubarb. From choosing the right time and place to plant it, to caring for it through the seasons, here’s everything you need to know to grow rhubarb successfully. Important Note: Rhubarb contains oxalic acid, especially high in the leaves. Rhubarb stalks contain levels that are safe enough to eat, especially after being cooked, but rhubarb leaves should never be eaten by humans, pets or livestock. Composting leaves is safe because oxalic acid breaks down during the composting process. Where Can You Grow Rhubarb Rhubarb thrives in cooler climates and is hardy in USDA zones 3 to 8. It will require a period of winter chill to stimulate bud break and a vigorous spring growing period. Ideally this means at least 6-8 weeks of temperatures below 40°F (4°C). During the growing season, rhubarb prefers cooler temperatures, ideally between 55°F and 75°F (13°C to 24°C). The plant can tolerate temperatures slightly above this range, but high heat, especially above 90°F (32°C), can stress the plant, leading to poor leaf and stalk development. Rhubarb's preference for cooler temperatures makes it an excellent crop for gardeners in cooler climates. However, it can also be grown in warmer areas with some care, such as providing mulch to keep the roots cool and planting in a location that gets afternoon shade. The plant prefers an open site with full sun, though it can tolerate light shade. Well-drained, fertile soil is ideal. Rhubarb does not do well in waterlogged conditions, think "no wet feet" or roots in this case. When to Grow Rhubarb The best time to plant rhubarb is in early spring for colder areas, or in the fall if you live in a slightly warmer climate. This allows the plant to establish itself and take full advantage of the growing season. Early spring, when the soil begins to warm up, is typically the best time to plant, unless you have a warmer climate, then as mentioned above, rhubarb can be started in the fall. Regardless of when you plant them, the soil temperature should ideally be above 40°F (4°C) to ensure the divisions can establish themselves and start growing. Planting Rhubarb from Seed or Root Division Before planting rhubarb, we should discuss planting from seed or root division. Rhubarb seed is just that, a packet of seeds that will need to be planted and germinated. A root division (also referred to as a "plug" or "crown") is a part of a mature plant's dormant root clump. There are many plants that are just hard to grow from seeds, like strawberries and lavender. Rhubarb is also one of those plants. So I recommend planting rhubarb from root divisions. This method ensures that the characteristics of the parent plant are preserved, and you'll usually be able to harvest your rhubarb sooner than if you start from seed. Divisions should have at least one or two buds (also called "eyes"). They can be planted in early spring or autumn. This method ensures that the characteristics of the parent plant are preserved, and you'll usually be able to harvest your rhubarb sooner than if you start from seed. What I also love about planting from divisions is this. If you are in a warmer climate suitable for rhubarb, you can plant your divisions in late fall and let your plants get established before winter. Like strawberries, rhubarb is hardy enough to survive milder winter cold and will go dormant and come back strong in the spring. Sources When buying root divisions, look for sources that take the Safe Seed Pledge or are Non-GMO. Local, non-big box garden shops are a good source if your growing area is suitable for growing rhubarb. If you don't have any such shops, I recommend a few online suppliers. Filaree Farm Renee's Garden Jung Seed Esty sources with good reviews. Preparing the Bed Rhubarb can be successfully grown in various garden setups, including standard in-ground gardens, raised beds, and pots. The best choice depends on your available space, soil conditions, and climate. I chose to plant my rhubarb in my in ground raised mounds. Someday I may experiment with other options, but I knew that if my rhubarb was successful, it would need a permanent place in my garden like my asparagus patch. Preparation is key to growing successful rhubarb. Start by enriching the soil with plenty of organic material, mature manure or compost. Rhubarb plants are heavy feeders and will benefit from this nutrient boost. Ensure the bed is well-dug and free of weeds. A pH of 6.0 to 6.8 is ideal for rhubarb. While changing pH of soil takes time, there are things you can do to adjust for it. But patience is a must here. If your pH is higher (alkaline) incorporate organic matter such as peat moss, pine needles, or composted leaves into the soil. These materials tend to be more acidic and can help lower the soil pH over time. If your pH is lower (acidic) incorporate materials that contain calcium carbonate. Natural materials containing calcium carbonate include wood ash from untreated wood and crushed eggshells. Dolomite lime and ground oyster shells are also a relatively inexpensive way to reduce acidic soil. Best Spacing for Growing Rhubarb Rhubarb plants need a lot of room to grow. A mature rhubarb plant can reach up to 2 to 3 feet tall (60 to 90 cm) and spread outwards to about 3 to 4 feet (90 to 120 cm) wide. The size of the plant will depend on the variety, growing conditions, and how well it's cared for. Space your plants about 3 to 4 feet apart in rows that are 3 to 4 feet apart. This spacing allows for adequate air circulation and room for growth, and also minimizes the risk of disease, fungus and the inability to see pests. How to Cultivate Growing Rhubarb Rhubarb requires minimal maintenance once established. Common sense garden hygiene will help to make sure your rhubarb stays strong and healthy. This includes managing weeds, trimming plants, mulching and water management. Weeds As with any garden, keeping weeds away ensures plants don’t fight for water and nutrients in the soil. Weeds also make good homes for unwanted pests. And they can make your garden look not-so-pretty. Pruning Rhubarb Trim off dead and dying leaves. This will help to prevent disease, improve air circulation, and improve the overall appearance of your garden as well. Be sure to use clean, sharp scissors or pruning shears to make clean cuts. This prevents damage to the remaining healthy parts of the plant and reduces the risk of introducing diseases. Be sure to dispose of the removed leaves properly, ideally by composting them away from your garden area if they are not diseased. If the leaves are diseased, it's best to discard them in the trash to prevent spreading pathogens to your compost pile or garden. Mulching Rhubarb Mulching rhubarb improves moisture retention, weed suppression, and temperature regulation of the roots. Use organic mulches such as straw, compost or shredded leaves. (I like to use pine needles that we gather when we take trips to the mountains. Pine needles are a perfect mulch that breaks down and helps to acidify my high pH soils.) A 2 to 4 inch layer is a good target, but be sure to leave some space around the base of the stalks to prevent moisture buildup directly against the plant, which could lead to rot. Watering Rhubarb And don't forget water. Rhubarb prefers consistent moisture, but doesn't like to be soggy. Consistent moisture is most important during the active growing season in spring and summer. Rhubarb plants typically need about 1 inch (2.5 cm) of water per week, whether from rainfall or irrigation. During hot, dry periods, this may need to be increased to 1.5 inches (3.8 cm) per week to ensure the soil remains moist. The best way to determine if your rhubarb needs watering is to check the soil moisture. The soil should be moist but not waterlogged. If the top inch (2.5 cm) of soil feels dry to the touch, it’s time to water. It’s better to water deeply and less frequently rather than shallowly and often. Deep watering encourages the development of a strong root system. If you’re watering by hand, aim the water at the base of the plant rather than over the leaves. Early morning is the best time to water, as it allows any water that does get on the leaves to dry quickly during the day. Feeding and Fertilizing Rhubarb As already mentioned, rhubarb is a heavy feeder. To thrive, rhubarb plants require a balanced supply of macronutrients and micronutrients. To ensure rhubarb has all the nutrients it needs, consider a compost tea in the early spring just after new growth begins and another round of compost tea again in 30 to 45 days after the first dose. Compost tea can be added as a foliar spray, hand poured at the base of the plant, or through drip irrigation. After harvest (late spring to early summer) work in compost round the base of the plant and consider another round of compost tea to help replenish nutrients used during the season's growth. Rhubarb would benefit from a final dressing of compost during winter before new growth and when before moisture events like snow and rain so that the nutrients can break down into the soil and be readily available for the next growing season. Inorganic fertilizers can certainly be used to feed rhubarb. It is recommended to feed a balanced granular fertilizer, such as 10-10-10 NPK, and apply according to the package instructions. Typically, about 1 cup of balanced fertilizer per plant in early spring is sufficient. Feeding rhubarb plants naturally and organically focuses on enriching the soil with natural, sustainable nutrients to support healthy growth and development. Organic fertilization methods not only nourish the plants but also improve soil structure and encourage beneficial microbial activity. When and How to Harvest Rhubarb Rhubarb Harvest Waiting Period Let's start with WHEN to harvest rhubarb. Short fast answer: Second season is ok, but waiting for the third year is the best. Rhubarb is a lot like asparagus. It needs some serious time to develop a solid root foundation in order to come back year after year. Think about it like this, you have to grow a superhero size root system because when you harvest, you will be taking nearly the entire plant and new growth every year. The root system must be robust enough to withstand such a loss of the upper plant. So rule of thumb… DO NOT harvest your rhubarb in the first year. It actually takes TWO full growing season to establish a serious and solid root system to ensure your plant is strong for the rest of its perennial life. You might think, "What if I planted my root division in the fall? Wouldn't the fall be considered the first growing season?" The answer is no. Planting in the fall just gives your plants that extra time to grow more robust root systems. Rhubarb is typically ready for harvest in its second spring, but it’s wise to wait until the third year to begin seriously harvesting. This patience allows the plant to establish a strong root system. Knowing When to Harvest Rhubarb Now that we have established the waiting period for harvesting. Let's discuss knowing when what harvest ready rhubarb looks like. Rhubarb is usually ready for its first harvest in spring, from April to June, depending on your location. The exact timing can vary with local climate conditions and the variety of rhubarb. The plant should have several stalks, ensuring that harvesting a few won't harm its growth. A healthy rhubarb plant can typically spare a few stalks for harvesting. Using color to determine readiness is won't quite work with rhubarb. Color can vary depending on variety. Some stalks can be red, some green etc. Harvest rhubarb stalks when they are about 12 to 15 inches long. At this length, they should be the best in tenderness and flavor. Stalks should be firm and have a good thickness, roughly around 1 inch in diameter, though this can vary with variety. Thin, spindly stalks may not have developed fully and can be less flavorful. They are ready when you can grasp them at the base and twist the stalk slightly to pull it away from the plant. Never harvest all the stalks from one plant, as this can weaken it. Alternatively, you can cut the stalk at the base with a sharp knife. Always leave at least two to three stalks on the plant to ensure continued growth and health. Also, remove and discard the leaf immediately, as it is toxic if ingested. Caring for Rhubarb After the Growing Season Once the growing season is over, remove any dead leaves to discourage pests and diseases. Apply a generous layer of compost or manure around the plants to replenish nutrients and protect the roots over the winter. In colder regions, a layer of mulch can provide additional insulation. In the fall, let leaves die back naturally, then cut back the rhubarb to the ground after the first frost has killed off the leaves. This will help to keep your rhubarb healthy and productive for the following year. The dead leaves can be composted. Do not compost diseased leaves, throw them in a separate garbage. Winter Protection for Rhubarb Rhubarb is a cold-hardy perennial that can survive winter temperatures as low as -20°F to -30°F (-29°C to -34°C) without significant damage. However, while the plant itself can survive these low temperatures, the root system is susceptible to damage if the ground freezes deeply and thaws frequently. In areas prone to extreme cold and significant freeze-thaw cycles, apply a layer of mulch over the crowns after the ground begins to freeze. This will help to insulate the soil and keep temperatures more consistent, protecting the roots. What To Do With Rhubarb The best and most important part of growing rhubarb is enjoying it. Rhubarb brings unique flavor for pies, jams, and more. As I explore more uses for rhubarb, I will update with recipes. Until then, enjoy a bountiful rhubarb harvest for years to come. Rhubarb Harvest