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Feeding raspberries: when to fertilise & the best plant food for raspberries
Being hungry feeders, raspberry plants require extra nutrients to support their vigorous growth and heavy fruiting. Read on to learn more about when to feed raspberries and what to fertilise them with.
For a bountiful harvest, raspberries (Rubus idaeus) need to be pruned correctly and provided with enough nutrients and water to support their vigorous growth. This article will cover how and when to fertilise your raspberry plants and what fertiliser to use.
Contents
Feeding raspberries: is it necessary?
Feeding raspberry plants isn’t strictly necessary as if they are planted in relatively fertile soil, they will produce a crop come harvest time. However, raspberry plants use up a lot of energy producing their vigorous canes and delicious berries, especially when grown in pots and richly benefit from supplementary feeding. Raspberries can also fall prey to pests and diseases, which can weaken the plants.
Correctly fertilising raspberries can help keep them strong and healthy, so if disease or pests do strike, they are less likely to succumb. If the foliage yellows it can often be caused by a lack of iron or magnesium, which fertilising can not only help prevent, but reverse if necessary.
When to fertilise raspberry plants
When you feed your raspberry plants is almost as important as whether you fertilise them or not, as there are key stages of a raspberry plant’s growth when they need the extra nutrition. These key times are when planting and in early spring as the growing season begins.
Granular fertilisers are often slow-release and can provide nutrition for weeks or months on end. However, this does mean that they need to be applied with forethought and in advance of the flowering and fruiting, for which they are needed.
When growing raspberries in containers with limited soil, feeding is even more crucial and nutrients need to be applied more regularly. On top of a granular feed in spring, it is advisable to apply a liquid feed every four weeks throughout the growing season to replace any leached or depleted nutrients. When repotting raspberry plants in spring, a slow-release fertiliser can be mixed into the fresh compost to give the plants a boost for the coming season.
Should you fertilise raspberries in autumn?
There is a slight danger when feeding raspberries in the autumn, as if the temperatures rise periodically, new growth may be stimulated leading to potential frost damage when the temperatures drop again. Furthermore, heavy winter rainfall can cause the nutrients to be washed away into natural drainage systems and negatively affect the local water system. Hence, it is advisable to only feed raspberry plants in the spring or late summer.
Should you fertilise raspberries when planting?
Raspberry plants thrive when grown in a fertile, moisture-retentive and free-draining soil and ground preparation is a key part of planting raspberries. Whether planting bare root or potted plants, it is advisable to not only enrich the soil, but provide the key nutrients necessary to help the new plant get off to a good start. Before planting, the addition of some well-rotted manure or garden compost will help improve the soil’s structure and fertility. Furthermore, a general slow-release fertiliser or blood, fish and bone meal mix added on planting, will provide some extra nutrition to support vigorous cane production.
Fertilising Raspberries summary:
- Prior to planting, enrich the soil with well-rotted manure or compost.
- On planting add a slow-release general fertiliser.
- Annually, in early spring apply a slow-release granular fertiliser high in potassium.
- If required, another slow-release application can be given in June.
- For container-grown raspberries, apply a slow-release fertiliser when potting up and feed monthly with a liquid fertiliser from June until September.
What to feed raspberries: choosing the best fertiliser
When it comes to the best feed or fertiliser for raspberries there are several different choices, from organic to synthetic options and those that are manufactured or homemade. Here are some of the most commonly used fertilisers for raspberries.
Raspberry organic fertilisers
Organic fertilisers are those that are derived from animal or plant sources. They contain nutrients such as nitrogen, potassium and phosphorus and other trace minerals including iron and manganese that are essential for plant growth. From homemade compost and well-rotted manure, which not only feed but help condition the soil as well, to commercially available slow-release pellets, there are many available. If space allows and you can make your own garden compost or comfrey liquid fertiliser this is ideal, if not high potassium fertilisers or manure pellets are widely available and suitable for applying. If adding manure to enrich the soil, it must be well-rotted, as when applied fresh its high levels of nutrients can burn and damage the plants.
Tip – Granular fertilisers are often slow-releasing and can feed plants for up to three months. However, when working them into the soil be mindful of the roots below, which can easily be broken.
Tomato feed for raspberries
Tomato feeds contain high levels of potassium and can be used to help encourage raspberries to flower and fruit. Our Plantura granular tomato food is made from 100% natural ingredients and is ideal for applying in early spring or summer, as being slow-release it can feed the plants for up to three months. Not only does it contain the necessary potassium and phosphorus to help promote flower and fruit production, but also nitrogen which will support the plant’s growth.
- Perfect for tomatoes, chillies, courgettes, cucumber & more
- For healthy plants & an abundant tomato harvest
- Long-lasting fertiliser that is free from animal products - child & pet friendly
As mentioned earlier, when it comes to feeding raspberries grown in pots, a liquid fertiliser can be easier to apply as it is diluted in water when irrigating and given every four weeks. Similar to our granular tomato food, the Plantura Liquid Tomato Food contains the key potassium and phosphorus to encourage flowering and fruiting and can be applied as soon as the first flowers appear.
- Perfect for tomatoes & other vegetables
- Liquid fertiliser for healthy plant growth & an abundant harvest
- Quick & easy application - child & pet friendly
Mineral fertilisers on raspberries
Mineral fertilisers can be provided in granular or liquid forms and are sometimes used for soft fruits. Synthetically derived from mined minerals or artificial forms, their water-soluble nutrients are often provided in high concentration and can be rapidly absorbed by plant roots, leading to quick results. However, due to their high concentrations, these fertilisers if misapplied, can lead to rapid over-fertilisation and plant damage.
Coffee grounds as a fertiliser for raspberries
As a common household by-product, spent coffee grounds can also be used to fertilise raspberry plants. Providing nitrogen and other trace elements, used coffee grounds can help support vigorous growth, but being acidic they should only be used in moderation and not after September.
As well as fertilising, raspberries need to be cared for in other ways to help encourage a good crop. Here you can read all our other tips on growing and caring for raspberries.
