Rhubarb crowns are the portions of a rhubarb plant located under the ground's surface that consist of rhizomes and buds. The plant spreads and grows via the rhubarb crowns, and new plants can be propagated by dividing them. Unlike the reddish stems that grow from them, the crown and leaves of the plant are not edible. Maintaining healthy crowns is vital for the production of a strong harvest. Rhubarb is a hardy plant that can be grown in vegetable gardens with relative ease; it can be afflicted with crown rot, however, which is very damaging to the plant.
When considered as part of the whole, rhubarb crowns are extremely important to a plant's overall health even though they are located underground. They function as roots, drawing nutrients and water from the soil. They consist of fleshy rhizomes, which are spreading horizontal stems, and areas of new growth known as buds. They are responsible for the rhubarb's spread and growth, and any damage to the crown can have adverse effects on the entire plant.
Rhubarb is usually not planted from seeds; whole or divided rhubarb crowns are purchased from a nursery, garden center, or catalog and then planted. When planting the crown, the soil should be prepared by loosening it and mixing in compost or manure along with a small amount of fertilizer high in phosphorus and potassium. The rhubarb crown should be placed in the soil approximately 1 to 2 inches (2.5 to 5 cm) deep for the best results. Once the plant has sprouted and has some growth above ground, a layer of mulching material can be added to help preserve moisture and prevent weeds.
Rhubarb crowns can be used to propagate the plant by division. It's best to do this when the rhubarb plant is about six to 10 years old in the very early spring. The crown can be dug up while the plant is dormant and divided into pieces the size of a fist; each one should have a large root portion and at least one bud. Once the new plant starts to develop, it's advisable to wait at least a year before harvesting the edible leaf stalks, and to pick them sparingly the second year.
The maintenance of the rhubarb crowns in a healthy state is important for the strength of the whole plant. Strong crowns produce bigger harvests and allow the plant to spread in a more vigorous manner. Rhubarb is normally a hardy plant that grows well with minimal care in cooler temperate areas. It occasionally develops crown rot from Phytophthora fungus, which usually kills the plant since it doesn't respond to antifungal agents. The best treatment is prevention by planting rhubarb crowns obtained from reputable sources in well drained soil.