This article touches on all the barriers to successful fruiting as well as the most frequently asked question. Each section is self-contained, so you only need read what you don’t know. If you are only to read one section, I’d recommend pollination – the number one barrier to successful fruiting.
Time to Fruit
Fruit trees are supplied as one or two year old trees, which take best once planted. Transplanting mature trees is not recommended, as they fail to replicate their productivity and often die. Nearly all fruit trees birthdays are in November.
Different species produce fruit at different ages.
Rootstocks influence a tree’s size (vigorousness) and time to fruit. Dwarfing or semi-dwarfing rootstocks take less time and vigorous rootstocks more. Dwarfing rootstocks are best chosen choice if you want fruit in a few years.
Varieties take different times to bear fruit with commercial varieties taking the least.
Pruning affects a tree’s time to fruit with trees putting their energy into growth, rather than fruiting. Heading stimulates growth the most and thinning the least.
Tying new shoots as to weigh them down can simulate the production of fruit buds, which will form next year’s crop. It is especially effective with apple trees.
Overfeeding, especially during fruit season, will cause a tree to put energy into growth at the expense of fruiting. Young trees should produce 30-45cm of shoot growth with mature trees producing 45-60cm. Hence, if your tree’s shoot growth is above or below the range, adjust your fertiliser input accordingly.
Removing competing plants, including grass, and replacing them with mulch will reduce competition and improve soil structure. Planting companion plants will improve yields by attracting pollinators.
Late frosts can damage, and sometimes destroy, a tree’s blossom. Blossom is required for pollination and pollination for fruit. Likewise, extreme weather will negatively affect pollinators.
Different species have different light requirements, although most prefer full sun. Plants that can cope with shade are usually shrubs, which can be found in the wild growing alongside other plants. Planting your trees in full sun is especially important in the UK, where the greatest problem affecting fruit yields is a lack of sunlight. Therefore, it is important to plan your garden before you plant.
The sun rises in the east and sets in the west, travelling across the southern sky. South facing gardens are preferred as a house will never cast a shadow across the garden. North is considered the worst as it produces a shadow during peak sunlight hours, while west and east provide shade in the morning and evening respectively.
Other than full sun, it is important to note how different planting positions can affect trees. As cold air collects at the lowest point it can reach, the temperature at the bottom of a sloping site is colder than at the top. Hence, to protect blossom from frost damage, plant late flowering trees at the bottom and early flowering trees at the top.
Secondly, sheltered areas both protect blossom and pollinators from strong winds, ensuring greater productivity. They also allow a tree to grow taller, faster. Look at an isolated tree upon a hill and compare the thickness of its trunk with that of a tree at the bottom.
Most fruiting species have both self-fertile and self-sterile varieties. Varieties that are self-sterile will not produce fruit without a pollination partner. Self-fertile varieties will, but also benefit from a pollination partner for heavier crops. Some varieties are partially self-fertile and can produce fruit alone, although it is often poor in quality.
In order for pollination to occur, self-sterile varieties require a compatible donor in bloom and pollinating insects to transfer the pollen. With many species, such as apple, it is probable that there is already another tree available to pollinate, especially if you live in an urban area. For others, such as sweet cherries, pollination is complicated as varieties require a specific type of pollen, and may not be pollinated even if another is in bloom at the same time.
As self-sterile varieties need another variety in bloom at the same time, varieties are put into flowering groups. As a rule, varieties in neighbouring groups will pollinate one another, but +/-2 may not. Specific flowering dates are best ignored. Group 2 will always flower later than group 1, and 3 later than 2 and so on.
Some species have triploid varieties, such as Bramley’s Seedling, that can’t fertilise others, but can be fertilised by others. Thus triploids need to be partnered with a self-fertile variety or two self-sterile varieties.
With some species closely related varieties will not pollinate one another. This is the case for cherries that require grouping with a universal donor for pollination. It is also the same for apples. Golden Delicious, for example, won’t pollinate Jonagold or Crispin due to genetic similarity. Hence, it is useful to partner trees with different origins – a traditional European variety with an Australian or American.
It should be noted that bees discriminate between different coloured flowers. Firstly, bees have an innate preference for violet and blue flowers, which have the highest concentrations of nectar. Secondly, and more importantly, the colour of the first flower a bee harvests pollen from will be a bee’s preference from then on. Hence, if a bee first harvests from a blue flower, it will have a strong preference for blue, foregoing radically different colours. This is why we recommend you plant a crabapple with similar colour blossom to that of apples (white with a touch of pink) such as ‘Golden Hornet’.
Sometimes ornamental species will pollinate the fruiting varieties as with crabapples and apples, and sometimes they won’t as with cherry blossom and sweet cherries. Some ornamental species, such as crabapples are considered excellent pollinators due to their widespread compatibility and long flowering times.
The greatest threat to pollination is unseasonal and extreme weather that can damage blossom and pollinators. This is especially a threat to early-flowering species, such as apricot, as well as less hardy species, such as peach, whose blossom can be destroyed by frost. It is recommended that you plant in sheltered, sunny spots, away from strong winds, which insects are naturally attracted to.
Some species’ flowers are more attractive to pollinators than others. Pear blossom, for example, are less attractive than apple due to their pale coloring and light odor. Thus, a bee may abandon a pear to pollinate an apple. Likewise pollinators can be distracted by flowering weeds, so remove them and plant companion plants such as daffodils, dill and echinacea.
As plants are pollinated by insects, avoid insecticides! Widespread use of pesticides is believed to have caused a 75% drop in flying insects over the last 25 years.
As pollination allows plants to breed, and produce genetically different offspring, seeds and therefore nuts can change in taste. If an almond tree is fertilised by a peach, it produces bitter nuts.
Pollen can be transferred via a paintbrush or cotton swab. Simply rub a brush over as many flowers as possible. Commercial operations often rent colonies of bees during flowering times.
A self-sterile tree without a pollination partner will not produce fruit altogether. A poorly pollinated tree will produce small and misshapen fruit. You can tell the quality of an apple by its seeds. A well-pollinated apple will have seven to ten.
Soil science is complicated, but the key message to take home is that plants prefer good structure, which allows optimal levels of oxygen and water to reach plant’s roots. Below is a succinct explanation of the different soil textures as well as soil pH, but if you want a full explanation please read our two articles: Everything You Need to Know About Soil and How Much Compost Do I Need For My Planter?
Soil is formed of a mix of broken down rock and humus (organic matter). The three soil particles are clay, silt and sand, which differ in the size of their particles (<.002mm, .002-.05mm and .05-2mm respectively). The smallest particles are clay and the largest are sand. The different size particles each have different drainage profiles with sand draining quickly and clay slowly. They also have different nutrient profiles with sand low in nutrients and clay rich in nutrients. Thus, as particle size increases drainage increases, but nutrients falls.
Particle composition determines a soil’s texture or type. Most soils are a mix of particle sizes, the most famous being loam. Comprised of 40% sand, 40% silt and 20% clay, it is both fertile and drains well. Soils primarily composed of smaller particles (clay, silt) are vulnerable to compaction and poor drainage, while soils primarily composed of larger particles are low in nutrients and often drain too quickly (sand).
They both need to be improved with organic matter (compost) that improves the soil’s structure, binding the particles into peds (aggregates). With clay and silt soils, the organic matter acts to increase porosity, improving the water holding capacity. With sand soils, the organic matter adds nutrients and increases the number of micropores, again improving the water holding capacity.
Excessively alkali or acidic soils lead to both key nutrients becoming unavailable for uptake and nutrients becoming available to such an extent that they are toxic. Most fruiting plants will suffice in a large range of pHs, the exceptions being the acid-loving blueberries and cranberries.
Hardiness refers to a tree’s ability to withstand cold. As a rule, nearly all popular fruit trees can withstand the UK’s winters, with many originating from far colder climates. Rather, the problem is the damage extreme weather can inflict on blossom and pollinators, which affects a tree’s productivity.
Trees acclimatize over a long period, becoming resistant to extreme cold. Hence, the cold tolerance of a mid-winter tree is substantially different from an early-winter tree, with unseasonal early or late extremes inflicting the most damage. They also de-acclimatize in response to warm temperatures, so a consistently cold winter is preferred.
Hardy trees have a long chilling requirement – the number of hours of cold endured before de-acclimatising and restarting growth. They are also able to distinguish between un-seasonal and seasonal warmth, with the former increasing the chilling requirement. Once a chilling requirement is satisfied, trees lose the ability to re-acclimatize, becoming vulnerable to extremes.
As a tree’s hardiness is dependent on recent temperatures, it can be hard to predict how frost will affect a tree. Blossom is vulnerable in all the stages of growth and buds may darken and die in response to extremes. For peach blossom, frost tolerance can vary up to 6 celsius during the bud period, and up to 3 celsius during blossoming, so the similar temperatures can have wildly different effects year-on-year.
As plants’ flower at different times of the year, some are more susceptible to damaged blossom than others. And as the date of the last frost differs significantly throughout the UK, early-flowering species’ blossom is more likely to become damaged in the north than the south.
It worth noting that cold air collects at the lowest point it can reach. Thus, the bottom of a sloping site can be substantially colder than the top, creating a frost pocket.
Some fruiting plants can’t endure the UK’s winters, requiring frost protection or moving indoors. These include exotics, such as passionfruit, and some varieties of grape. These plants can be killed down to the root or destroyed altogether in left unattended.
Once dormant, potted plants will happily suffice in a garage, outbuilding or greenhouse, but should not be brought into the house as a combination of heat and warmth will cause them to come out of dormancy.
It should be noted that pruning in late-autumn decreases the cold hardiness of a tree, so it is best avoided for early-flowering species and exotics.
After frost damage blossom, the greatest issue affecting fruit tree yields in the UK is the lack of sunlight. Growers in Australia and Chile can produce much heavier crops due to the consistent hours of sunlight. Hence, it is important to plant your tree as so it receives maximum sunlight.
Jorge works in the Primrose marketing team. He is an avid reader, although struggles to stick to one topic!
His ideal afternoon would involve a long walk, before settling down for scones.
Jorge is a journeyman gardener with experience in growing crops.