GROWING berries RASPBERRIES

GROWING RASPBERRIES

A raspberry is a sweet/tart, edible fruit produced by a raspberry cane (Rubus idaeobatus). Pound for pound, raspberries are by a wide margin the most prolific of the berry bushes, producing more fruit and more new raspberry plants than any single berry bush.

Modern cultivars of raspberry are meant for fresh eating and fruit tends to be large and slightly drier, which allows them to last on the bush without rotting as quickly. Also, they can keep for up to a week in refrigeration.

Old fashioned raspberries, like Meeker, tend to be smaller, juicier, delicate and more fragrant, but require daily picking to prevent fruit from spoiling.

Raspberry canes are grown worldwide in temperate climates with mild-to-warm summers and have been cultivated into several different varieties.

There are many named cultivars of raspberries, so it is important to choose one that is right for your taste preferences, uses, and location.

Choosing a Variety

Size

Raspberries are all similar sizes that can be maintained at approximately 5’-6’ tall at maturity. Left unpruned many cultivars can reach 8'-9' tall.

Type

Raspberries come in two types: Everbearing and Summer-bearing, with the difference being in fruiting timing. Summer-bearing cultivars make fruit once a year in the warm mid-season on two-year old wood, called floricanes. Everbearing raspberries give fruit twice a year, once in the early warm season on the floricanes and again towards the end of the warm season, on new first-year canes called primocanes. The individual harvests of Summer-bearing types tend to be larger than Everbearing ones, though Everbearing raspberries produce slightly more fruit over the course of the year.

Pollination

Raspberries are self-fertile, meaning they do not require cross pollination with other varieties of raspberries to produce fruit, but as with other self-fertile plants, raspberries may yield more heavily with a pollination partner nearby. Pollinizer plants should be of the same type, but a different variety, and planted no further than 50' apart to ensure good access for pollinators.

USDA Plant Hardiness Zone

Raspberry bushes are hardy to USDA zones 4-8, unless otherwise noted. This rating tells you the minimum winter temperature the plants typically survive when properly hardened off. Make sure you consult the USDA Hardiness Maps website, which provides information on the average minimum winter temperature in your location, by zip code. Your USDA Plant Hardiness Zone does not reflect the many of the other factors in successfully growing raspberry bushes, including length of growing season, rainfall amounts, soil quality, and chill hours. Consult your local extension service for more detailed information about your local growing region and the factors you will need to know when selecting plants for your berry patch.

Chill Hours

All plants have what are called a "chilling hour requirement" in order to flower and produce fruit. Chilling hours are defined as the cumulative period of time between 45 and 32 degrees Fahrenheit and vary from region to region. The majority of fruiting plants have a chilling hour requirement of anywhere from 500-1000 hours, with some requiring more and a few requiring as little as 200-300 chill hours to blossom and produce. Raspberry bushes that require less than 600 chilling hours are considered "low chill" and are generally more resistant to more intense summer heat conditions than raspberries with higher chilling hour requirements. The general chilling hours available for your specific location can be found online or determined by your local county agricultural extension office.

Where to Plant your Plant

Raspberry bushes need to be planted where they receive at least 6 hours of direct sunlight measured in early summer (late June to early August). Sufficient sun exposure triggers the initiation of new flower buds for the next growing season, without which there will be no fruit. Fruit ripening and flavor development are also benefited by the carbohydrate production stimulated by the sun, as well as its heat. Despite the sun-loving nature of raspberries, note that raspberries do not tolerate intense summer heat and should be planted to receive the morning sun and if possible be shaded from the afternoon sun, especially in hot summer regions.

Raspberries tolerate a wide variety of soils so long as they are well drained and moderately rich with a pH around 6.3-6.8. Improve your soil where you intend to plant by mixing an inch or two of plant or animal-based organic matter (compost), peat (if your soil is alkaline), or coconut coir into a patch usually 3-5 feet wide and 8 feet long or longer and up to a foot deep. A 2-4” deep layer of mulch (straw, leaves, or wood chips) applied after planting will continue to improve the soil and help it hold water.

Canes should be planted deep enough that the top roots emerging from the base of the cane stub should just be covered by your soil. Covering the roots too deeply will delay, or inhibit, the emergence of new crowns from the base of the cane stub. Extra-long roots should be laid sideways and buried by 2-4" of soil. Do not be surprised if nothing emerges from the cane stub - most new crowns will emerge from the base soil or along the root of the dormant canes.

Allow sufficient space for both the top of the plant and its roots when selecting the planting location. Don't be afraid to prune your canes to your desired height. Creating a simple box trellis system can keep your canes from laying down in pathways when heavy with fruit.

Be sure to include enough space between patches for transporting supplies in and fruit out. Using a sharpened shovel to outline the bed in spring and fall by slicing into any roots attempting to migrate out of your patch will keep your patch outline tidy and your access clear. Additionally, raspberry beds need to be rotated, which new raspberry stock, approximately every 5 years due to potential fungal disease buildup in the soil. Make sure to plan out your next bed before you need it!

Growing in Containers

Raspberries that have been bred specifically for container culture can grow very well in pots as small as 10 gallons. Be sure to thin the old canes and prune your raspberries for height to maintain them in a container. Standard raspberries tend to grow and spread too aggressively to be happy all but the largest pot or trough. Remember that containers are hotter and drier than in-ground plantings and your raspberries will require more fertilization and irrigation than those planted in the soil.

Use 1/4 soil from your garden in the pot, 1/2 should be a light potting mix with added vermiculite or perlite, and the rest can be compost. For larger pots use a potting mix that has a larger particles in addition to smaller ones.

Care and Maintenance

WATERING YOUR PLANTS

This is the most important and often the most difficult part of successfully growing plants. There are many factors, including the humidity, temperature, soil type, wind, and amount of direct sun that affect how much and how often water should be applied.

A general rule of thumb for plants in the ground is to ensure they receive an inch of water per week over the root zone. An inch of water is equivalent to about ¾ to one gallon per square foot of soil surface area. The typical three foot diameter planting hole would need 7 ½ to 10 gallons of water per week provided by rainfall or by the gardener.

Apply this water once a week, two times per week if soil is fast draining or temperatures are consistantly above 80F. This will of course depend on your own conditions and the plants you are growing! DO NOT water lightly each day because this results in a wet surface and dry root zone area. The soil should be moist but not soggy to a depth of about a foot for most growing plants. The top inch or two can feel dry, and the plant still be well watered. The trick is to have the water available where the roots are. In hotter and sunnier areas, a mulch of straw, bark, etc. can greatly ease the burden of summer watering. For plants in containers, water until the soil is saturated and water comes out of the drainage holes. Very dry pots can be placed in a water-filled saucer or tray until the entire container has soaked up all available moisture. Let the container dry until the soil is dry to the touch 1 to 2 inches down (more deep with deeper pots) and the container is lighter in weight. A plant that has wilted can be receiving either too much or too little water.

In rainy areas like the Pacific Northwest most of the plants that we offer will need relatively little supplemental irrigation ONCE THEY ARE WELL ESTABLISHED in the ground and have had a chance to develop a good root system. However even here it is important to make sure plants have regular, deep watering during the first couple of growing seasons, and the first 2 summers is especially critical. In drier areas, or where soils do not retain water well, permanent irrigation is essential. Remember that you don’t want your plants to just survive, but rather to thrive! Make sure they get the water where they need it. Drip irrigation and soaker hoses can be an efficient way to deliver the water. Water-stressed plants can drop developing fruit, ripe fruit can be less succulent, and stressed plants can be more subject to disease.

Fertilization

For good steady growth and high productivity, your plants need to have adequate amounts of various mineral nutrients. Some people are fortunate and have naturally rich, fertile soil.

Use an all-purpose or bloom-producing fertilizer if necessary. A couple of inches of well-rotted compost on the root zone can also be an effective fertilizer. A generous leaf or straw mulch on your patch will not only conserve moisture and help in weed control, but also keeps your soil healthy by building up humus, attracting earth worms, and supporting beneficial fungal organisms. This encourages raspberries to be strong, healthy and productive. Excessive use of fertilizer can increase disease problems on your plants and can even kill them, so natural and gentle is always best.

As a general guide, if your raspberry patch is producing new crowns and vigorous canes each year and has healthy looking foliage, it may not need much or any fertilizer. If the patch shows signs of decline, you can apply fertilizer to see if that will revitalize it. If there is no improvement, then prepare to dig up and destroy all old canes, and create a new raspberry patch with fresh, virus-free stock in a new location, at least 15 feet from your previous area.

Pest and Diseases

Comments

Injury occurs during pattern of warm days followed by freezing nights. Sap gets stuck in trunk, freezes, then rapidly thaws in the warm sun the next day, rupturing cells.