Redcurrant

Light and exposure

The redcurrant accepts full sun as readily as partial shade, a flexibility that is rare among fruit shrubs. In sun the clusters are sweeter and more abundant. In partial shade, under a light tree or against an east facing wall, it produces a little less but the fruit stays juicier and ripens later, which spreads out the harvest.

This tolerance makes it the fruit shrub for the difficult corners of the garden, the ones that only see sun for part of the day. Under a cool, often overcast sky, a spot with morning sun and shelter from cold winds gives the best results; under a hot summer, look for afternoon shade instead. Either way, do not hesitate to place one in a slightly shaded angle where nothing else wants to grow.

Watering

The redcurrant likes a cool root run, as it is a woodland plant by origin. In open ground and once established, it copes very well with the rainfall of a damp temperate climate and only needs watering during the rare prolonged droughts, above all while the fruit is forming and swelling, between flowering and harvest. Under a hot dry summer, watering becomes regular instead.

For the first two years after planting, be more attentive while the root system fills out. A good mulch at the base, dead leaves, dried grass clippings or compost, keeps the soil cool and moist, cuts down on watering and feeds the plant. It is the single most useful thing you can do for a happy redcurrant.

Soil and repotting

Undemanding, the redcurrant still prefers a cool, deep, humus rich soil that holds moisture without being waterlogged. It grows in most garden soils, including the somewhat heavy, clayey ones, provided they are not permanently soaked.

It likes slightly acidic to neutral soils and dreads above all an excess of lime, which can cause chlorosis, a yellowing of the leaves between the veins. At planting, enrich the hole with well rotted compost and mulch generously. An input of organic matter each autumn keeps it vigorous year after year.

Temperature and humidity

This is a perfectly hardy fruit shrub, built for cold and temperate climates. Once dormant it shrugs off -30 °C without flinching, which puts it at ease from USDA zone 3 to 7. A spell of winter cold is actually necessary for it to flower and fruit well the following spring: it needs 800 to 1500 hours below 7 °C, and it is that chill requirement that makes it fail where the winter stays mild.

Its heat tolerance, on the other hand, is moderate: it is at its best under cool humid summers, and under a hot summer it asks for afternoon shade and a soil kept cool. The other point to watch is late spring frost, which can scorch the early flowering in a fickle year. The redcurrant flowers early, ahead of most other fruit shrubs, and a touch of frost on the flowers reduces the harvest. A slightly sheltered spot and a position that avoids frost hollows limit this risk; apart from that, the plant asks for no winter protection.

Pruning and upkeep

Pruning makes sense once you know where the redcurrant fruits: on two and three year old wood, that is to say neither on the very young shoots of the current year, nor on exhausted old wood. The aim of pruning is therefore to keep a rotation of young productive branches going, by removing the wood that is too old.

You prune in winter, during dormancy, from leaf fall to bud break, outside frosty spells. On an established bush, keep about ten framework branches of staggered ages and remove each year the oldest branches, those over 3 or 4 years old, along with dead, broken or tangled wood in the centre. This renewal pruning opens up the bush, lets light in and maintains a steady crop of good quality.

Pests and diseases

The redcurrant stays robust overall, but a few troubles recur under a damp climate. American powdery mildew covers leaves and young shoots with a white mealy felting, especially in heavy, humid weather, so open up the bush well by pruning to keep it in check. The currant blister aphid causes very characteristic red puckers and swellings on the leaves, spectacular but rarely serious, and a spring spray of soft soap on the colonies is usually enough.

Watch also for the currant clearwing, a moth whose caterpillar tunnels inside the stems and makes them die back, so cut and burn the affected wood. But enemy number one remains without question the birds, blackbirds and others, which devour the clusters just as they ripen. The only really effective remedy is a fine mesh net laid over the bush as soon as the fruit begins to colour.

Propagation

The redcurrant propagates with disconcerting ease from hardwood cuttings in autumn, and that is the method to know. At leaf fall, take well ripened shoots of the current year, twenty to thirty centimetres long, remove the lower buds, and plant them two thirds deep straight into open ground in a sheltered corner, or in a pot. The strike rate is high, winter and spring do the rest, and you get free new plants for the following autumn.

Layering also works very well: in spring peg a low branch down into a small trench, keep it in the ground, and it roots in one season and can be separated in autumn. These two methods, simple and needing no equipment, explain why the redcurrant passes so easily from garden to garden.

Month-by-month care calendar

Green Hub tips

• Lay the bird net as soon as the clusters begin to colour: blackbirds empty a redcurrant in a few days, it is by far the number one enemy of the harvest.
• Remember the pruning rule: the redcurrant fruits on two and three year old wood. Remove the wood over 3 years each winter to keep a young productive bush.
• At leaf fall, take hardwood cuttings of the current year, planted two thirds deep in the ground: the strike is almost guaranteed and you multiply your plants for free.
• Pick by the whole cluster rather than berry by berry, it is quicker and it damages the fruit less, which in any case keeps for only a short time once picked.
• Mulch the base permanently: the redcurrant, a woodland plant, loves a cool root run, and the mulch spares it the stress of the dry spells of summer.