Rhubarb is a perennial plant in the Polygonaceae family. Rhubarb plants have large stalks that produce leaves and flowers. The stalk is the portion of the plant that is eaten, and the flower and leaves are discarded. Although rhubarb is used mostly for pies and jellies, it is considered a vegetable.
Harvest rhubarb when the stalks are between 10 and 15 inches long. The stalk is the celery-like, curved reddish portion of the plant. If all of the stalks have not grown to this size, do not remove the smaller stalks.
Remove only a few stalks of rhubarb the first year it has been planted. Although new rhubarb plants can withstand a very light harvest, pulling every stalk off the new plant will weaken it and possibly keep it from growing in future years.
Don't depend on the color of the stalk. Different varieties of rhubarb produce bright red stalks (the Ruby and Valentine cultivars) while others (the Victoria and Linneaus cultivars) are usually only red at the bottom of the stalk when the rhubarb is ready for harvest. Just because the rhubarb is not entirely red does not mean it should not be harvested.
Cut the stalks you wish to harvest with a sharp knife. Cut as close to the base of the plant as possible, without injuring any small plants that may still be growing. Trim off any excess leaves after washing the stalks.
Remove flowers as they grow. Even if you are not harvesting your rhubarb this year, pinch off the small flowers that grow on top of the stalks. These flowers take nutrition from the stalk and can prevent it from growing to its full size.
Rinse any dirt or debris from the rhubarb stalks and blot thoroughly with a paper towel to remove excess water.
Cut the stalks into 1-inch chunks. Lay the chunks out on a cookie sheet in a single layer with none of the chunks touching.
Place the cookie sheet in the freezer and leave until the chunks of rhubarb are frozen solid. Open-freezing like this usually takes 5 to 6 hours, but a good rule of thumb is to leave them overnight so you are certain they are well frozen.
Put the frozen chunks into a labeled freezer bag and press out any air before you seal it. Store the bag in the freezer for up to a year. One pound of rhubarb should give you about three cups of chunks.
Maturity and Selection
Split only mature rhubarb plants, from three to five years old, that have produced a full harvest. Younger plants need their stored nutrition for growth. Additionally, if excessive seeding was a problem with some of the rhubarb plants in your garden last year, then do not select those particular plants for splitting. Better-quality plants tend to sprout fewer seed stalks, according to the University of Illinois Extension.
When to Split
Split rhubarb when the plant is dormant. A good time is in early spring, before the last frost date for your area. The U.S. Department of Agriculture publishes last frost dates for all regions of the country.
Splitting the Crown
One way to propagate rhubarb is by splitting the crown into two, three or four pieces. Cut the crown in half. If each piece has at least two roots with buds, split each half into two pieces. Transplant the rhubarb into its new place in the garden.
Splitting the Roots
Splitting the roots is another way to increase the number of rhubarb plants. Dig up the roots and identify the buds. Cut the roots so that each piece has one or two buds. You should get from four to eight cuttings, depending on the number of strong buds.
Harvest rhubarb through mid-summer, then allow the plants to grow foliage for energy absorption. Cut off any late-summer flower stalks because these waste plant resources.
Mulch the rhubarb plot after the first frost of the season, when temperatures drop to 40 to 50 degrees F. Once the foliage dies, cover the crowns with 2 to 3 inches of straw, wood chips, bark or dried leaves for protection. Lay landscape blankets on top of the mulch in zones 3 and 4 for additional cold protection.
Remove 1 to 2 inches of mulch in spring. Mix the remaining mulch into the soil around the plants for additional nutrition and soil drainage. Put the plants back on their spring and summer water and nutrition schedules for continued growth.
Cut the stalks close to the base and then remove the leaves. Rhubarb is ready for harvesting when the stems are red and magenta.
Plant your Gunnera in partial sun or shaded areas and near water, if possible. Choose locations with moist, rich soil and enough room for the full size of the Gunnera to mature. Remember to wear gloves when working with your Gunnera plant because of the sharp spines.
Water your Gunnera plant as needed to maintain moist soil conditions throughout the growing season. Cover the area around the plant with 3 to 4 inches of mulch to help maintain the damp conditions needed and prevent weeds.
Apply a basic fertilizer, such as 10-10-10, each spring or early summer to your growing Gunnera, and then drench the area with water. Follow the directions on the label for proper amounts.
Cut the Gunnera back to ground level each fall or cover the top of the plant with several inches of straw for protection through the winter months. Some gardeners remove the giant leaves, place them over the rest of the plant and then add the mulch on top of the leaves.
Buy rhubarb crowns or divide the ones in your garden when you first see buds in the early spring. Use a sharp knife to divide them, and make sure each part has a bud or two and a couple of inches of roots. Place in the ground immediately after dividing.
Find a location in full sun or partial shade. Plant rhubarb crowns on raised beds in soil fortified with compost or rotted manure. These supplements will help ensure adequate drainage so the crowns don't rot. Plant 4 to 5 inches deep and at least 3 feet apart to avoid crowding.
Apply a complete fertilizer when you plant in spring and again in late autumn. Put it around the plant but not touching the crown. Water enough to keep the soil moist, but don't flood the plants.
Wait until the second year to harvest your rhubarb. From late spring into summer, harvest stems that are at least an inch wide by cutting them off at ground level.? Leave smaller stems to help growth the following year.?