Growing raspberries in containers has both benefits and drawbacks for backyard gardener. The best choice for container gardening are smaller and sturdier, everbearing raspberry variants, but all other will do fine, if proper conditions are met.
Growing raspberries and other plants in containers has many benefits:
- it is easier to adjust the soil and optimize it for the plant that is actually grown in container,
- plants with containers can be moved around as required or needed,
- growing raspberries in containers prevent them from spreading around the garden, etc.
One of the drawbacks is that raspberries require more or less constant moisture in the soil in order to grow properly developed and healthy fruit - you can't simply leave them for days without watering during summer heat and expect them to grow and bear fruits. Raspberries that are grown in the garden soil patch also must be regularly watered, but they are less susceptible to drought than raspberries grown in containers.
Preparing the Soil in Containers
Soil for raspberries must be slightly acidic (pH 6.0 - 6.2), must retain nutrients well, but also must have good drainage.
Depending on the raspberry variety and desired number of plants, 40cm (16 inches) round pots are large enough for single plant. Larger pots, 50-60cm (20-24 inches) or even larger, are suitable for several plants.
Start filling the container with 2-5cm (1-2 inches) of gravel that will help with the drainage - be sure that container has enough drainage holes. Fill the rest of the pot with mixture of good potting soil, aged manure and humus/compost. Also, add some balanced NPK fertilizer with gradual release of nutrients. If you don't have aged manure, add fresh one to the mix, cover the pot and let it settle for a month - don't let rain to wash away nutrients from the soil mix.
There are other possible combinations based on available raw materials - peat moss, perlite and similar. If you have relatively heavy soil and plan on using it for a soil mix, add some sand, perlite, aged manure, peat moss and similar materials in order to increase water and nutrient retention, with good drainage of excess water.
Adding hydroton pebbles can increase water retention, but also aeration of the soil - as water evaporates from hydroton pebbles or as it is absorbed by plants, fresh air enters the soil and pebbles themselves.
On the other hand, hydrogel (water) beads, pearls and powders absorb water and change volume, without forcing fresh air in and old air out of the soil - if 'right' conditions are met, such conditions can lead to growing problems, including root rot and various diseases.
Planting and Maintaining Raspberries in Containers
Raspberry plants should be purchased from reputable nurseries as dormant bare-root or as potted, virus-free plants. If you are a novice gardener and you don't need many raspberry plants, go for potted raspberry plants.
When soil in container is ready, dig a hole large enough to accommodate young plant's roots. Cover the roots with the soil, press the soil and water thoroughly with stale rainwater. Ordinary water will do fine, of course, just try not to water with cold water. If setting of the soil occur, add more soil and mulch in the form of wood chips, sawdust, straw and similar.
Mulch protects the soil from heat and wind, keeping the moisture in. Also, it helps against weeds even in the containers. However, mulch also must not prevent young shoots from growing, so it should not be too thick and too heavy.
If support is required, add it right away, since pressing the poles in the soil at later time can damage the roots and new shoots.
Although raspberries are heavy feeders, too much of nutrients, especially nitrogen, leads to large, but weak plants prone to pests, diseases and physical damage.
As said before, young raspberries should be planted in slightly acidic soil rich in organic matter, with added aged manure, compost/humus and balanced NPK fertilizer. In the similar manner, in late winter, add some aged manure, compost/humus and balanced NPK fertilizer to fruit bearing plants. As plants grow, add nutrients in the form of liquid fertilizer once or twice per month. If you have NPK fertilizer with gradual release of nutrients and it is combined with aged manure and humus/compost, refeeding is not required for next 3-4 months.
Watering plants in containers is very important - if possible use dripping system that will keep moisture level on almost constant level. If not, water manually 2-3 times per week, depending on the size/volume of container, size and number of raspberry plants in container and temperature. During summer heat, water daily with stale water.
Proper amounts of nutrients and water are very important for everbearing raspberries. Harvest of common raspberry varieties can last 2-3 weeks at most and this can be prolonged by growing several different types of raspberries. However, everbearing raspberries produce berries in the spring and again in the autumn. Mixing everbearing and ordinary raspberries in the garden is the best way to have fresh, great tasting raspberries from your own garden for months, constantly.
Depending on the location, raspberries should be pruned until middle of the May. Remove anything that is damaged or ill, remove two-year old canes and one-year redundant canes. Canes bearing fruits should be cut to the height of 1.2-1.5 m (4-5 feet), depending on the variety. Raspberries in the containers can grow as very thick bushes, so keep the number of the canes at moderate level. Letting the sun and air into the bush, decreases the danger of various diseases.
Common Everbearing Raspberry Varieties
When obtaining raspberries, the best option is to get certified virus-free, one-year old plants. However, those who have time and patience, can grow desired varieties from the seeds. Seeds can be purchased locally or from on-line shops. Most popular everbearing raspberry varieties are:
- Heritage - medium-sized fruits, self-supporting plants,
- Sweet Repeat - large, sweet, red berries, not many thorns (not thornless!), tolerates high temperatures,
- Autumn Britten - large and sweet berries, high yields, very adaptable plants,
- Anne - golden, sweet raspberries lacking tartness of some red raspberries,
- Golden Fall (Fall Gold) - yellow, sweet berry, moderate crops,
- Jaclyn - large, juicy berries, very resistant to wind and rain, requires support due to heavy yields,
- September - tart and juicy, medium sized berries,
- Caroline Red - ripens early, resistant to root rot, large berries,
- Redwing - large and sweet berries, moderate crops, self-supporting plants.
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Everbearing raspberries are hardy and prolific plants, bearing fruits even in the cold, wet weather. However, to avoid losses of berries due to early autumn frost, plants and berries must be protected by some sort of cover (thin nylon, for example). Also, letting the dormant raspberry plants to spend late winter indoors, makes them start to grow earlier in the spring - don't leave them overnight outside too early in the spring, since late spring frost can make some serious damage to the plants.
Growing Raspberries from Seeds
Raspberry seeds are very small, so handle them with care. Depending on the number of desired plants, fill suitable tray with low-nutrient, sterile, seed-starting potting soil, press it firmly and water with stale water. Space raspberry seeds an inch apart (2.5 cm), cover with thin layer of the same potting soil or fine sand and water again using spray bottle and stale water.
The best time for sowing the seeds is during winter - even if you buy stratified seeds, they need some time to get going.
Cover the tray with transparent plastic or nylon and keep the soil moist. Place the tray near the window facing the north in cool room.
When outside daily temperatures reach 60°F (15°C), place the tray outside in partially shade. Sometimes it takes 4-6 weeks for raspberries to germinate.
Be sure to keep the soil always lightly moist.
When plants develop first pair of mature leaves, transplant individual seedlings into 4-6 inch (10-15 cm) pots filled with good potting soil. In the beginning, keep them in partial shade and water regularly.
One year old raspberries grown from the seeds can be planted on permanent location just as one year old raspberries purchased in garden centers.
Note: it is normal for some home gardeners to choose the best raspberries from the market, let them over-ripen for few days at home, remove and dry the seeds, place the seeds into the refrigerator for a month and then to sow such seeds - results can be surprisingly good with few disappointments here and there :)
Common Growing Problems
Raspberries don't have many growing issues.
If they are grown in well aerated soil with good drainage, root rot will not occur. Regular watering and plenty of nutrients support strong feeder like raspberries.
When buying plants, plants must be healthy and virus-free. When sowing the seeds, be sure to use good, preferably sterile, potting soil.
Raspberries prefer sunny locations, but will, up to the point, tolerate semi-shade positions, depending on climate and varieties. Since they are in the pots, move them if required.
Prune bushes from excess canes and let the sunshine and air in the bush - this way leaves, flowers and berries dry quickly and are more resistant to various diseases.
Some varieties tolerate wind, but winds can break shoots and canes, reducing the yield - grow raspberries protected from strong winds and strong rainfalls.
When berries start to ripen, birds can be a problem - if required, add some sort of protective nets to prevent pest from feeding on ripe raspberries.
Harvesting the Raspberries
Harvesting the raspberries at home garden should be done when berries are fully ripe. Unlike industrial production, goal is to prolong harvesting season and that is done by choosing right varieties.
Raspberries are picked every second or third day from the same plant and with enough plants and varieties, raspberry season can last for months and they can be harvested on a daily basis and consumed fresh or processed into jellies and juices or prepared as part of pies and cakes or they can be frozen for later use.