Features of growing common raspberries

How a Raspberry Bush Is Structured

Underground, the raspberry forms a rhizome – a perennial part of the stem from which new shoots grow every year. On the roots (especially in red raspberries), adventitious buds are formed – from these, root suckers emerge. It is through these suckers that raspberries spread sideways and fill the row (Tarasov et al., 1981; Yaroslavtsev, 2003).

Black and purple raspberries do not produce root suckers – new shoots develop only from buds on the rhizome. This is important to consider when choosing a variety and planning plantings (Cornell Guide to Growing Fruit at Home, ch.5).

First Year of a Shoot's Life (Primocane)

In spring, a green shoot emerges from a bud on the rhizome or from a root sucker – this is called a primocane (replacement cane or annual shoot). During the summer, it grows in height, leaves develop on it, and in the axil of each leaf a bud is formed.

By late summer – early autumn, when shoot growth slows, the apical and lateral buds begin to transform from vegetative to generative (flower) buds. This process is called bud differentiation. In summer‑bearing varieties, it occurs under the influence of short days and lower temperatures (Funt, 2013; Crandall, 1994).

Important: in the first year, the shoot does not branch (unless the tip is damaged). All flower buds are located in the leaf axils along the stem, and they remain dormant.

By autumn, the annual shoot becomes woody, loses its leaves, and enters winter. Its height can reach 1.5–2.5 m depending on the variety and conditions.

Second Year of a Shoot's Life (Floricane)

The following spring, the overwintered shoot (now called a floricane) does not grow in height – its apical point is no longer active. Instead, fruit branches (laterals) begin to grow from the lateral buds formed the previous year. Buds appear on them, then flowers, and after pollination – ovaries and berries (Crandall, 1994).

Flowering in raspberries is extended: flowers on the upper fruit branches open first, then gradually those lower down. Therefore, berries do not ripen all at once, and harvesting can last 3–4 weeks. This is a feature that gardeners use to have fresh berries over a longer period.

The fruiting cane lives until it has given its crop. Immediately after the berries are harvested (or a little later, depending on the climate), it begins to die. Dieback proceeds from top to bottom, and by late summer – autumn the cane is completely dry down to the rhizome (Tarasov et al., 1981).

What Happens After Dieback

While the biennial stem is fruiting, new annual replacement shoots are already growing from the rhizome and roots. They will appear in spring, develop through summer, and by autumn they will have set flower buds – to provide the next year's crop. This process repeats year after year.

Thus, in each raspberry bush there are simultaneously:

• biennial canes (floricanes) – they bear fruit in the current season;
• annual canes (primocanes) – they will ensure next year's crop.

This knowledge underlies the main pruning rule: spent biennial canes are removed immediately after picking the berries, so as not to shade or weaken the young annual canes that will bear fruit next year.

Practical Takeaways for the Gardener

1. Do not prune annual green shoots in summer – they are next year's crop. Remove only diseased, broken, or excessively weak ones.

2. Immediately after harvest, cut out the spent biennial stems at ground level – do not leave stubs. This improves light and air circulation in the bush, reduces disease risk, and gives young shoots more nutrients and light (Buckingham, 2010).

3. Monitor the number of root suckers – if there are too many, the bush becomes dense, berries become smaller, and the risk of fungal diseases increases. A moderate number of suckers (5–10 per linear metre) is optimal for a good crop (Cornell Guide to Growing Fruit at Home, ch.5).

4. Knowing the cycle, you can plan the replacement of old bushes. The rhizome lives 8–12 years, then productivity declines. By that time, you will already have young suckers that can be transplanted to a new location to rejuvenate the planting.

Special Features of Black and Purple Raspberries

These types do not produce root suckers, so they do not spread. New shoots grow only from buds on the rhizome. This is convenient for small plots, but requires more careful propagation – they are propagated by tip layering or horizontal layering, not by dividing the rhizome (Yaroslavtsev, 2003; Crandall, 1994).

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Where Flower Buds Come From

Everything starts in the autumn of the previous year. On annual shoots (primocanes) that grew over the summer, buds are laid in the leaf axils. In late summer – early autumn, when shoot growth slows, under the influence of short days and lower temperatures these buds begin to transform from vegetative (leaf) buds into generative (flower) buds. This transition is called differentiation (Crandall, 1994; Funt, 2013).

In summer‑bearing varieties, differentiation begins at the top of the shoot and gradually moves downward to the base. Therefore, the largest and best‑developed flower buds are usually located in the middle part of the stem, while the weakest are at the tip and at the very base (Tarasov et al., 1981). This pattern explains why pruning recommendations advise removing the shoot tip – there the berries will be small and inferior anyway.

Practical conclusion: for buds to form fully, the canes need enough time to mature. Excess nitrogen in the second half of summer delays wood ripening and impairs flower bud initiation – therefore, nitrogen fertilisers are applied only in spring and early summer.

How Fruit Branches Develop in Spring

The following spring, after the danger of severe frosts has passed, fruit branches (laterals) begin to grow from the overwintered buds. They bear leaves, buds, and then flowers. The strongest fruit branches develop from buds in the middle part of the stem – they produce the largest berries. Upper buds give short, weak branches with small berries, while lower buds often fail to break at all (Tarasov et al., 1981; Crandall, 1994).

Pollination: Self‑Pollination or Bee Help

Raspberry flowers are bisexual – each flower has both stamens (male organs) and pistils (female organs). Most varieties are self‑pollinating, meaning they can set fruit from their own pollen (Crandall, 1994; Yaroslavtsev, 2003). However, pollination quality is significantly improved when flowers are visited by insects, especially bees. Bees transfer pollen from flower to flower, resulting in more seeds being set, and therefore more drupelets in each berry.

Why this matters: each drupelet (the individual “bead” in the berry) develops only from a pollinated pistil. If pollination is incomplete, the berry becomes small and misshapen (crumbly), with bald patches. The better the pollination, the more drupelets in the berry and the larger it is (Crandall, 1994).

Practical conclusion: attract bees and other pollinators to your site by planting nectar‑rich plants nearby. In cloudy, cold, or windy weather, bee flight is limited, so fruit set quality declines – keep this in mind if spring is unfavourable.

Fruit Structure and Three Stages of Growth

The raspberry fruit is an aggregate of drupelets (commonly called a berry). It consists of many (75 to 150) small drupelets, each containing one seed and surrounded by fleshy pulp. All drupelets are firmly joined together and sit on a common receptacle. When ripe, the drupelets of raspberries easily separate from the receptacle, and the berry is picked as a “thimble” with a hollow cavity inside (Crandall, 1994; Funt, 2013).

Berry growth proceeds through three stages, each requiring specific conditions:

1. First stage (cell division) – immediately after pollination. Cells divide very rapidly, establishing the entire future number of cells in the berry. At this stage, size barely increases (only about 10% of final weight), but the number of cells is determined right now. For good cell division, nitrogen and sufficient water are needed. If the plant is starved or suffers drought during this period, berries will be small because fewer cells will be laid down (Crandall, 1994).

2. Second stage (seed development) – growth slows (less than 5% increase). During this time, the seed coat forms, and the embryo develops inside. If pollination has not occurred, the seed aborts and the drupelet stops growing.

3. Third stage (final swell) – the most important: it accounts for about 85% of the final size and weight of the berry. At this time, the cells laid down in the first stage enlarge greatly, accumulating sugars, acids, and aromatic compounds. For filling, water and carbohydrates (sugars) produced by leaves in sunlight are needed. Any lack of moisture or shading during this period drastically reduces berry size and flavour (Crandall, 1994).

Practical conclusion: watering is especially critical at the beginning of berry growth (first stage) and during the filling period (third stage). Moisture deficit in these phases cannot be compensated later – the berries will remain small.

Extended Flowering and Ripening

Raspberry flowering is not simultaneous: first, the uppermost flowers on the strongest fruit branches open, then those lower on the branch, and only later do the branches in the lower part of the stem start to flower. As a result, flowering lasts 3–4 weeks, and berries ripen gradually. This means that the harvest is spread over a month or more – up to 10–12 pickings per season (Tarasov et al., 1981).

This property is convenient for the gardener: fresh berries can be collected over a long period. But for processing (jam, freezing), it requires planning. On the other hand, extended flowering is a natural insurance against frost: if early flowers are damaged, later ones may survive and give at least part of the crop.

Compensation: Why You Should Not Be Afraid to Thin

Raspberries have a remarkable ability – compensation. If the number of shoots per unit area is reduced (e.g., by thinning), the remaining shoots produce longer fruit branches, set more berries, and the berries themselves grow larger. In total, the overall yield may not drop as much as one might expect, and the quality of the berries improves noticeably (Crandall, 1994).

This means that thinning shoots and removing excess suckers is not a loss of yield, but a redistribution in favour of larger, healthier berries. A dense, unthinned bush gives many small berries that are difficult to pick and more susceptible to disease.

Factors That Reduce Yield

Gardeners should know the main reasons why the crop may be poor:

• Insufficient pollination – especially in rainy or cold weather when bees are scarce. Result: small, crumbly berries.
• Lack of moisture during cell division and filling – berries remain small and dryish.
• Nutrient deficiency – especially nitrogen in spring (for shoot growth and flower bud initiation) and potassium (for berry quality and size). Excess nitrogen in the second half of summer, on the contrary, is harmful (Crandall, 1994; Funt, 2013).
• Overcrowding – lack of light reduces photosynthesis, berries become smaller, and diseases develop more readily.
• Frost damage to flowers – although raspberries flower relatively late, in some regions late spring frosts can damage buds.
• Diseases and pests – especially grey mould (botrytis), raspberry beetle, and raspberry cane fly.

Main Practical Takeaways for the Gardener

1. Next year's crop is set in the autumn of the current year – ensure the canes mature and do not overfeed with nitrogen.

2. In spring and early summer, pay attention to watering – especially during flowering and the early stages of berry growth.

3. Attract bees – this noticeably increases berry size and completeness.

4. Do not be afraid to thin – removing excess shoots improves the quality of the remaining berries.

5. Harvest berries on time: overripe ones drop off, while underripe ones do not accumulate sugar.

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1. Shoot Renewal: The Foundation of Planting Longevity

As we already know, each raspberry shoot lives for two years and dies after fruiting. If spent canes are not removed, they shade young shoots, serve as a reservoir for diseases and pests, and also take away nutrients that could go towards new shoot growth (Buckingham, 2010; Cornell Guide, ch.5).

Renewal rule: immediately after harvest (in August), cut out all spent biennial stems at ground level, leaving no stubs. The earlier this is done, the better for the young shoots: they receive more light, air, and nutrition, have time to strengthen before winter, and set full‑sized flower buds (Funt, 2013, ch.10; Tarasov et al., 1981).

How to distinguish an old stem from a young one: the bark of a biennial stem is usually darker, peeling, greyish‑brown; an annual stem is light green or greenish‑purple, smooth (Yaroslavtsev, 2003). In addition, after fruiting, old stems show dry fruit stalks.

Simultaneously with removing old stems, remove all weak, damaged, crooked, or inward‑growing young shoots – they will not give a good crop and only thicken the planting.

Why it works: by cutting old stems, you redirect the flow of nutrients and water to the young shoots that will bear fruit next year. In addition, air circulation improves, reducing the risk of grey mould and other fungal diseases (Crandall, 1994, ch.9).

2. Density Regulation: There Should Be Just Enough Shoots

One of the most common mistakes made by gardeners is allowing raspberries to spread uncontrollably. The result is a “jungle” where shoots compete for light, water, and nutrients, berries become smaller, yields drop, and diseases spread rapidly.

Optimal density depends on the variety and growing system, but there are universal guidelines:

• In the row, leave 4–6 of the strongest annual shoots per linear metre (Buckingham, 2010; Cornell Guide, ch.5). With denser planting, berries become small; with too sparse, yield decreases due to incomplete use of the area. Per square metre, this is roughly 5–8 shoots for the floricane type with row spacings of 2–2.5 m (Funt, 2013, ch.12).

• Row width should not exceed 30–45 cm. All shoots that extend beyond this boundary are removed – either dug out (if needed for propagation) or cut at ground level (Cornell Guide, ch.5; Funt, 2013, ch.10). A wider row worsens light penetration and makes harvesting difficult.

• Root suckers that appear between rows must be regularly removed – either by digging or mowing. If left, they become competitors and eventually independent bushes, creating chaos (Crandall, 1994, ch.9).

When to thin? The main thinning is done in early spring (before bud break), when you can see which canes have overwintered well and which are damaged. Remove all weak, thin (diameter less than 1 cm), broken, or diseased canes. Also thin in late summer after fruiting, together with the removal of old canes (Funt, 2013, ch.10).

Why thinning improves quality: raspberries have a compensation trait – on fewer shoots, longer fruit branches and larger berries are formed (Crandall, 1994, ch.3). The remaining shoots receive more light, enhancing photosynthesis and sugar accumulation.

3. Trellises: Why and Which Type

Summer‑bearing raspberries, especially tall varieties, lodge without support, especially when canes are loaded with fruit. Berries fall to the ground, become dirty, rot, and are difficult to pick. In addition, wind easily breaks the loaded stems.

Types of trellises:

• Single‑row (simple) – posts every 5–8 m, with 2–3 wires (or strong twine) stretched between them at heights of about 0.5 m, 1.0 m, and 1.5 m. Canes are tied to the wire or woven between the wires. This is the most common and simple option for gardeners (Buckingham, 2010; Funt, 2013, ch.10).

• T‑trellis – a crossbar (0.5–0.6 m) is fixed on each post, and two parallel wires are stretched along the ends. This allows fruiting canes to be spread apart while young canes remain in the centre – improving light penetration to all layers (Funt, 2013, ch.10; Cornell Guide, ch.5).

• V‑trellis – posts are inclined in opposite directions, forming a V shape. Fruiting canes are tied to the outer upper wires, while young canes grow in the centre without shading the fruiting ones. This system has proven itself in commercial plantings, but can also be interesting for amateurs (Cornell Guide, ch.5).

When to install a trellis? Preferably before planting or in the planting year, so that shoot growth can be directed from the start. If installed later, tying already overgrown shoots is more difficult.

How to tie: canes are tied with soft twine or special clips to the wire, not too tightly to avoid damaging the bark. Spent stems, after cutting, free the trellis for young canes. Young canes that will bear fruit next year can be tied during the summer as they grow, directing them vertically upward (Funt, 2013, ch.10; Buckingham, 2010).

Why a trellis is necessary: it not only supports the canes but also improves light access to all layers, prevents lodging and contact of berries with the soil, simplifies pruning, disease control, and harvesting. Moreover, tied canes suffer less from wind and snow breakage in winter (Cornell Guide, ch.5).

4. Light: The Main Resource for Sweet Berries

Raspberries are light‑loving plants. In the shade, shoots stretch, internodes elongate, fewer flower buds are set, berries become smaller and more acidic. Maximum yield and best flavour are achieved only in full sun (Funt, 2013, ch.2; Buckingham, 2010).

How to ensure good light:

• Choose the sunniest spot on the site for the raspberry patch.
• Orient rows north–south (or according to the prevailing wind) so that the sun illuminates both sides evenly during the day.
• Control row width (no more than 30–45 cm) – only in such a narrow strip does each shoot receive enough light. In wide rows, the lower parts of the shoots shade each other.
• Timely remove excess shoots (see above) and spent canes – they create shade that hinders young shoots from accumulating nutrients.
• Do not plant raspberries near tall trees or buildings that cast prolonged shade. The optimal distance to obstacles is at least 2–3 m.

Light and berry filling: in the third stage (filling), berries need carbohydrates produced by leaves in the light. The more light the leaf canopy receives, the sweeter and larger the berries will be. Therefore, even slight shading during the ripening period noticeably worsens quality (Crandall, 1994, ch.3).

Additional nuance: in regions with very hot summers, light midday shade (e.g., from a sparse net) may be useful to avoid scorching berries and leaf burn. However, in temperate climates, full sun is preferable (Buckingham, 2010).

Summary Table: Four Principles in Action

Common Mistakes

• Delaying the removal of old canes – they shade young shoots during the most critical growth period, reducing future yields.
• Reluctance to remove shoots – many are afraid to cut “extra” shoots, resulting in dense bushes and small, sour berries. Remember: raspberries compensate for the loss of some shoots by increasing the productivity of the remaining ones.
• No trellis – canes fall to the ground, berries spoil, yield is lost, and caring for such a planting becomes extremely inconvenient.
• Planting in shade – even if raspberries survive, the crop will be poor and tasteless.

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Why Raspberries Suffer in Winter

The main factors of winter damage:

• Direct freezing of tissues at temperatures below critical thresholds. For red raspberries, the damage threshold for floricanes is about –28…–35 °C, for black and purple – –20…–26 °C (Funt, 2013, ch.2). However, even at less severe frosts, flower buds may die.
• Heaving of roots due to alternating frosts and thaws, especially on heavy waterlogged soils (Cornell Guide, ch.5).
• Desiccation (winter drought) – strong winds in frosty weather dry out cane tissues, especially the upper parts that have not matured (Crandall, 1994, ch.9).
• Damage by rodents – mice and voles damage the bark at the base of canes, especially under snow.
• Waterlogging during stagnant meltwater in spring, when roots suffocate from lack of oxygen (Cornell Guide, ch.5).

Therefore, winter preparation is a set of measures aimed at increasing winter hardiness, protecting against adverse weather, and preserving canes until spring.

1. Stopping Growth and Maturing of Canes

Young annual canes must have time to “ripen” before winter – their wood should become dense, and the bark should take on the characteristic colour of the variety. Immature, succulent canes suffer greatly from frost (Crandall, 1994, ch.9; Funt, 2013, ch.12).

How to help maturation:

• Stop nitrogen fertilisation from the second half of summer (no later than mid‑July in temperate climates). Nitrogen stimulates green growth, delays tissue maturation, and reduces winter hardiness (Crandall, 1994, ch.9).
• Reduce watering in late summer – early autumn, if there is no drought. Excess moisture in the soil also prolongs vegetation.
• Sow green manures (oats, rye, mustard) in the inter‑rows in late summer. They “absorb” excess nitrogen and moisture, promoting earlier growth cessation and better cane maturation (Crandall, 1994, ch.9). In spring, these green manures can be incorporated into the soil as organic matter.

2. Removal of Spent Canes

Although this operation is carried out immediately after harvest (see chapter 4), before winter check again that no old, dry canes remain. They serve as shelter for pests and disease pathogens that weaken the plant. In addition, old stems hinder bending down young canes for snow retention.

Cut out any remaining biennial stems at ground level, as well as all weak, thin, diseased, or damaged annual shoots, so that only the strongest remain for winter (Buckingham, 2010; Cornell Guide, ch.5).

3. Snow Retention: Bending and Tying Canes

Snow is the best natural cover for raspberries. Under a snow layer 40–50 cm thick, even in severe frosts, the temperature rarely drops below –5…–10 °C, which is safe for most varieties (Funt, 2013, ch.2). Therefore, in regions with snowy winters, the main task is to accumulate and retain snow in the raspberry patch.

How to do it:

• Bend the canes to the ground (or tie them in bundles and bend them) so that they are covered by snow. This is especially important for tall varieties, whose upper parts are most vulnerable.
• Do this before the onset of severe frosts, but after the first frosts, when the canes have become more flexible. Usually in late October – early November (timing depends on the region).
• For bending, tie the canes in small bundles (3–5 each) with soft twine, then carefully bend them to the ground and secure with arches or peg hooks to the soil. Do not overdo it – the canes should not break.
• In regions with stable snow cover, you can simply tie the canes together so that snow accumulates on them naturally. But bending is more reliable.

Note: this method is not suitable for regions where winter thaws followed by frosts are common – bending onto wet ground may cause bark rotting. In such cases, tying the canes in vertical bundles for wind protection is sufficient (Buckingham, 2010; Funt, 2013, ch.10).

4. Mulching the Root Zone

The raspberry root system is shallow (most roots are in the 20–30 cm layer), and in snowless frosty winters roots can freeze. In addition, mulch protects against heaving and conserves moisture.

What to use:

• Well‑rotted manure, compost, peat, straw, or sawdust (decomposed) in a layer of 8–10 cm around the bushes, but not right against the stems to avoid bark rotting.
• Apply mulch after the first frosts, when the soil has already slightly frozen (so that mice do not settle in the warm mulch).
• In spring, rake the mulch away so that the soil warms up faster.

Caution: fresh sawdust and straw can attract mice, so it is better to use decomposed organic matter or combine mulch with repellents (Cornell Guide, ch.5; Buckingham, 2010).

5. Protection Against Rodents

Mice and voles are a scourge of raspberry plantings in winter. They gnaw the bark at the base of canes, which can kill the entire above‑ground part.

Protection measures:

• Place poisoned baits or repellents (e.g., wormwood, elderberry) under the bushes before snowfall.
• Use fine‑mesh metal netting around the planting (30–40 cm high), sunk into the ground.
• Regularly remove debris and plant residues – they attract rodents.
• Tamp down snow around the bushes (especially after thaws) – compacted snow makes it harder for mice to move.

6. Covering in Snowless Regions

In areas with frosty but low‑snow winters (southern steppes, continental regions) or with frequent thaws, additional covering is needed.

Options:

• Cover with non‑woven fabric (agrospan, lutrasil) – thrown over bent canes and secured at the edges. The material breathes, allows moisture to pass, and protects from wind and temperature fluctuations.
• Spruce or pine branches – good insulation, retain snow, and repel mice.
• Dry leaves, corn stalks, reeds – but only if they are dry, otherwise they may compact and cause rotting.

Covering is removed in spring as soon as the threat of severe frosts has passed, so that the canes do not overheat.

7. Spring Assessment and Pruning of Damage

After snowmelt, inspect the canes. If the tips are frozen or blackened, cut them back to live tissue (usually to the first healthy bud) (Funt, 2013, ch.10; Cornell Guide, ch.5). This removal stimulates lower buds to break, which will produce fruit branches. Severely damaged canes are removed entirely, leaving only the strongest for fruiting (see thinning norms in chapter 4).

Important: do not rush with pruning – sometimes damage does not show immediately, and it is better to wait until buds start to grow to accurately determine the dieback limit.

Summary Calendar of Winter Preparation

Depending on the Region

• Zones with cold snowy winters (north, Siberia, north‑eastern US, Canada): main focus – snow retention (bending), rodent protection, mulching. Varieties should be as winter‑hardy as possible (e.g., 'Boyne', 'Killarney', 'Nova').
• Zones with mild but snowless winters (southern Russia, Ukraine, southern US states): cover with agrotextile or branches, protect from heaving and drying winds. Prefer varieties tolerant of temperature fluctuations ('Latham', 'Reveille').
• Zones with frequent thaws: avoid dense covers that cause rotting; use breathable materials and ventilate in time.

Main Conclusion

Summer‑bearing raspberries overwinter “with the whole stem”. How you prepare the planting for the cold directly determines whether there will be a crop next year. The main enemies in winter are not so much frost as lack of snow, desiccating winds, rodents, and improper covering. Therefore, act on the principle: “better to be over‑cautious than to end up with no berries”.

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When Summer‑Bearing Raspberries Win

When Fall‑Bearing Raspberries Are Preferable (for Objectivity)

For fairness, it is worth mentioning situations where fall‑bearing raspberries win:

• If you want to get berries from July to October (summer + autumn crop) – summer‑bearing cannot do that.
• If you prefer to mow all canes in autumn and not worry about wintering stems (but then you lose the summer crop).
• If your summer is hot and dry, while autumn is mild and long – fall‑bearing raspberries can give an excellent autumn harvest.
• If you need a crop in the very first year after planting (summer‑bearing gives the first full crop only in the second year).

Comparison Table for Choice

Final Decision: What to Choose

Ask yourself a few simple questions:

1. What matters more to me – maximum flavour or a long harvest period? If flavour – summer‑bearing.

2. How long is my summer? If short and cool – summer‑bearing.

3. Am I willing to cover/bend canes for winter? If yes – summer‑bearing; if no – fall‑bearing (but then you lose the summer crop).

4. Do I want to harvest berries in the very first year? Then fall‑bearing.

5. What is my plot like? If small and you need compact bushes without suckers – black/purple summer‑bearing.

Main advice: do not pit these two types against each other – on many plots, gardeners successfully grow both, obtaining both summer and autumn berries. Summer‑bearing varieties give the “classic” – the raspberry we have loved since childhood. Fall‑bearing ones extend the season. The choice is yours, but knowledge of biology will help you make the right decision.

Conclusion

Summer‑bearing raspberry is not an outdated crop, but a time‑tested choice for those who value quality, flavour, and reliability. Its cultivation is built on understanding the two‑year cane cycle, correct pruning, thinning, trellising, and winter protection. By following these principles, you will obtain stable harvests of large, aromatic berries for many years.

In this article, we have covered all the key aspects. Now your task is to apply this knowledge on your plot, taking into account your local climate and personal preferences. Good luck and bountiful harvests!