By Dr. Mercola
Best tasting straight from the bush, raspberries are perfect for your home garden and a tasty addition to a salad or as a snack. Growing your own will ensure you enjoy berries not sprayed with pesticides and insecticides. Although red raspberries are the most common, you have a choice of several varieties. They come in different colors, which ripen at different times of the year, allowing you to spread out your harvest.
Once harvested, consider adding to smoothies, homemade yogurt and garden salads and whipped into homemade salad dressings. To get the most from your raspberry harvest each summer, choose a plant variety for your climate zone, choose the best spot in your garden, prevent pests and disease and learn simple techniques to care and prune your plants.
These bite-sized berries come in several different colors. While red is the most common, both red and yellow are the hardiest and very sweet. Interestingly, purple raspberries are a hybrid of black and red raspberries. Black raspberries are delicious, and different from blackberries, but also are the least hardy and more susceptible to disease. When black raspberries are picked, the stem remains on the plant, unlike blackberries whose stem breaks off from the plant during picking.
Using a climate zone map,1 determine if you live in zones 3 to 9, as this is where raspberries generally grow best. The temperature zones estimate the lowest temperatures. In zone 3 temperatures can drop to as low as -35 degrees Fahrenheit (F) while in zone 9 temperatures don’t generally drop below 20 F. This wide range of temperatures means you have a higher likelihood of finding a variety suitable for your climate.
Most varieties of raspberries will ripen throughout the summer and fall months, giving you a long growing and harvesting season. However, some produce more fruit during the summer and others produce more during the fall. You may want to select several varieties to ripen at different times in order to enjoy a longer harvesting season.2
- Summer red raspberries ripen in early to midsummer.
- Everbearing red raspberries produce from midsummer into fall.
- Black raspberries can be found growing wild east of the Rockies and have only a short season beginning in early July and lasting approximately three weeks.3
- Golden raspberries are harvested throughout the fall months.4
- Purple raspberries are as productive as red raspberries and produce heavy crops that ripen in early summer.
Ideal Growing Conditions
Prior to planting, identify the variety best suited for your region. Most varieties love cool summers and mild winters, but several have adapted to hot, sunny climates. If you are growing your raspberries in a warmer climate, be sure they get afternoon shade. In cooler climates, they will grow best in full sun.
The bushes should be planted in well-draining soil, as standing water can rot the roots in a matter of days.5 If your yard does not have good drainage, consider installing raised beds and drainage pipes, or planting in containers. Growing in a container takes no more work than planting in the ground as the raspberries can be placed on a sunny patio and moved to the shade in the afternoon.
In theory, any bushy plant in the backyard can grow in a container, but the more compact plants will do better in a container as they don’t require support to stand upright.
Use a container at least 24 inches in diameter to allow the plants to flourish. This also helps with cold hardiness. The pot should be filled with a soil-based compost and the plants well-watered when they are added to the pot. As with plants in the ground, never allow the soil to completely dry out.6
The plants do best in soil with a pH between 5.8 and 6.2. Raise the pH level by amending it with lime, based on the results of a soil analysis. Your local university extension office is often able to provide this service. Raspberry plants can live up to 15 years or more, so early preparation of the bed will help ensure long plant life. Although the root system of the plant may not be deep, dig to a depth of at least 12 inches to loosen soil and remove rocks, ensuring good drainage, a critical element of the success of your plants.
Add too much water and the root system will rot, but too little water and your plants won’t produce fruit.7 Especially while fruiting, the plants require from 1 to 2 inches of water every week. If the soil is always slightly moist to the touch, but not soggy, the plant is likely getting enough water. Overhead watering may help spread disease. Instead, use a drip system or soaker hoses to provide your raspberry bushes with enough moisture for a good harvest.
Care and Pruning Increase Potential Yield
Viruses seriously weaken raspberry plants, so it is best to start with plants from certified virus free stock,8 as well as removing all wild raspberry plants from the area. As demonstrated in the featured video, you can purchase a dormant cane or a live potted plant to start your raspberry bush. Depending on the variety you choose, the plants can reach from 36 to 60 inches tall with a 24- to 36-inch spread.9
Dormant canes can be set out four to six weeks before the last frost in your area, while plants grown in containers should be planted after the danger of frost has passed. The plants should be set in the ground 1 inch deeper than they grew in the nursery containers. Before planting in the ground, dig out all weeds and amend the soil with mature compost or other high quality organic matter.10
Work this into the soil, ideally at least two weeks before you plant your raspberry bushes. This is also a good time to use a light application of lime or wood ash to raise the soil pH, if testing indicated it was needed. Place each plant 2 feet apart in the row, and each row at least 8 feet apart, to allow the plants to grow while still giving you room to walk in-between without being scratched by thorns.
The plants will send out shoots. Any coming up 12 inches from the base of the cane into the path between rows should be trimmed away as this significantly reduces the width of the walking area. Once planted, it’s time to give them 1 to 2 inches of water. Ensure the root ball is not exposed as this will quickly dehydrate the plant. A thick layer of natural mulch will help improve drainage, retain moisture and reduce weeds.
The pruning technique you use will depend on the variety you plant.11 All summer-bearing varieties should have weak canes removed at the ground level in early spring. Leave 10 to 12 of the healthiest canes and tip prune any suffering cold damage. Fall-bearing varieties can be pruned to produce one or two crops.
To get two crops, prune the plants as if they are summer-bearing; after the fall harvest, prune them to the ground. If you want one crop, there’s no need to prune in the summer, but cut all canes to the ground in the spring.
When the cane finishes producing fruit, it will naturally die. Remove the old canes by clipping them at the ground and pulling them from the top to encourage good air circulation in the plants and sun penetration to the leaves. This small step also helps reduce potential for disease.
You can prevent many problems with your raspberry plants by ensuring a sunny location with fertile, well-draining soil.12 Raspberries are sensitive to root rot, so avoid growing near tomatoes, potatoes or other plants susceptible to verticillium wilt. If an individual raspberry cane appears affected by disease, it may be the result of cane borer larvae. Simply cut back the cane to 6 inches below the damage to prevent further injury.
Raspberries are also susceptible to fungal disease resulting in the leaves turning a rust color.13 As the disease progresses, yellow pustules appear on the underside of the leaves, later turning black, containing spores that can overwinter. Finding a fungal infection early means you can remove the leaves, which may stem the spread. However, if the plant appears to be fully diseased, it’s necessary to remove the entire plant and closely watch the ones next to it.
Another common condition attacking raspberry plants is spur blight,14 having the greatest impact on purple and red raspberries. This is another fungal infection that attacks the leaves and canes and reduces your harvest. Leaves are often the first to show symptoms as the outer edges turn yellow and the leaves slowly die. Lower leaves are the first to be infected and when they fall the stem remains on the bush. During a severe attack, younger leaves toward the top are also killed.
Keeping the area weeded and the rows cut back to facilitate adequate drying and sun exposure will go a long way toward preventing disease. Fungal infections favor wet conditions and can be controlled by aiding good circulation through the canes by keeping the canes spaced well apart and allowing good sun exposure.
Harvest Your Delicious Berries and Leaves
Raspberries are ripe for the picking when they show good color and come off the stem easily. It’s best to harvest daily as the sun can scald ripe berries and prolonged rains can rot them.15 Place your berries in shallow containers, stacking no more than three berries deep and refrigerate immediately.
Wash and clean with cool water only just before preparing to eat or getting them ready to freeze. You can enjoy your raspberries through the winter months by freezing them on a shallow pan covered with wax paper. Once individually frozen for about an hour, transfer them to freezer-safe containers and use throughout the winter.
Your raspberry plants produce not only fresh fruit but also leaves for herbal raspberry leaf tea. Raspberry tea has been used to treat menstrual symptoms and ease childbirth.16 The leaves are rich in potassium, iron, manganese and B vitamins. Harvesting the leaves for tea should be done in midmorning, before the plant blooms and just after dew evaporates. This is when the essential oils and flavor in the leaves are at their peak.
Anytime you’re harvesting either berries or leaves, be sure to wear long sleeves and gloves for protection against the thorns. Leaves can be harvested anytime during the year. Choose young and vibrant green leaves for your tea. Wash them, pat them dry and lay them out on a screen to air-dry.17 Store dried leaves in a glass jar in a cool dry area out of the sun. When you’re ready to make tea, crush the leaves and use 1 teaspoon for every 8 ounces of boiling water. Steep for five minutes.
Valuable Health Benefits of Raspberries
Raspberries are high in vitamin C, quercetin and gallic acid.18 The high antioxidant value is thought to contribute to their ability to fight heart disease, circulatory disease, age-related decline and cancer. Raspberry oil has a sun protective factor and may protect against wrinkles. Consider making a facial mask blending 1 cup of plain yogurt with 2 cups of fresh raspberries until smooth. Apply to your face for 15 minutes before washing off with tepid water. The antioxidant power of vitamin C may help reduce age spots and discolorations.
Also high in ellagic acid, a chemoprotective agent with anti-inflammatory properties, raspberries may efficiently help stop damage to cell membranes. In combination with other flavonoid molecules found in raspberries, this unique blend of antioxidants also has some antimicrobial properties.19
The high nutrient value of the berries are proficient in helping reinforce your immune system to fight against disease. When grown in fertile soil, they are an excellent source of manganese and vitamin C helping to protect against oxygen-related damage. The combination of flavonoids and antioxidants in raspberries have demonstrated some memory improvement in animal studies and may protect against cognitive decline.20 The fiber and water content in the berries may also help prevent constipation.
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