Q. My red raspberries have done poorly with very little fruit production the last few years. What do you think is wrong?
A: Raspberries can be a bit tricky in certain situations.
Red raspberries were cultivated in Europe for centuries, growing wild as far south as Greece, north to Spain and as far north as Norway.
Red raspberry was gathered by the people inhabiting Troy from vines growing at the foothills there in the first century B.C. The Romans spread the seed of raspberries throughout their empire – all the way to Great Britain.
William Prince established the first plant nursery in the American colonies in 1737 in Flushing, New York, that offered raspberry plants.
Many raspberry cultivars produce a non-bearing cane the first year, that flowers and grows berries during the second season.
Sometimes the variety can make a difference with everbearing Heritage probably the most common raspberry in our area. Everbearing raspberry plants can bear two crops per year, one crop in the spring and the second in the fall.
One must prune out the canes that produced fruit in a current season, while allowing the canes that did not produce fruit to develop into fruit bearing canes the following season. If the potential fruit bearing canes are pruned, then little or no fruit will be produced the following year. The exception is Heritage, which can be simply mowed at the end of the season to produce one crop a year.
There are many kinds of raspberries, but all are members of the rose family. Rose family members generally prefer full sun and well-drained soils and are unfortunately susceptible to fungal diseases and various insect issues.
Cornell University released a study that compared disease and survivability to planting depth and soil type and found that raspberries grown in raised beds performed much better compared with those planted at soil level or below soil level, especially on heavy clay soils- which we have in our area.
Raspberries do poorly in overwatered or soggy sites. Drought conditions can also affect survivability, because the roots of raspberries are shallow and may require some supplemental watering during dry periods
Phythopera root rot can occur in poorly drained situations where the plant literally wastes away, cane blight is another fungal disease that causes similar symptoms. Raspberry cane borer can also destroy canes on stressed plants.
Raised beds work well for raspberries. Beds that are about a foot in height are appropriate. Use a blend of compost, Canadian sphagnum peat moss, professional grower’s mix and sand to fill the beds. You should not use a heavy potting mix or topsoil that contains mostly muck. These materials hold way too much water and will cause issues.
One can remove sod and till the materials into the soil, creating a similar raised bed.
Fertilize your raspberries using compost and well-rotted manure. Spraying the foliage with compost teas may help with fertility and disease issues. Drip irrigation during times of drought can also reduce disease problems.
The Plant Medic, written by Ricky Kemery, appears every other Tuesday. Kemery retired as the extension educator for horticulture at the Allen County Purdue Extension Service. To send him a question, email [email protected].