How to Grow Healthy Apples

Apples are a tradition of the Czech countryside. In recent years, however, instead of Czech varieties, global varieties have begun to be planted even in gardens, which are less resistant and, moreover, on weakly growing rootstocks. What needs to be done so that we don't end up with a sickly tree bearing ugly fruit in the garden?

What is a rootstock and how does it affect fruit tree growth?

If we propagated fruit varieties directly from seeds, the resulting trees would lose their desired characteristics due to genetics. Therefore, we graft desired varieties onto previously propagated rootstocks, which is an indirect propagation method. Rootstocks are obtained through seed sowing and vegetative propagation. Vegetatively propagated rootstocks have stable characteristics, typically weaker growth, and favorably influence fruitfulness. Generatively propagated rootstocks – from seed – have more vigorous growth in apple trees, are long-lived, delay fruiting but better cope with site stress. Rootstocks are designated by codes – letters and numbers that indicate the place of origin and the order in which they were bred.

Selection of rootstock and variety

Currently, vegetatively propagated rootstocks predominate in apple trees. There is a large number of these rootstock varieties. According to growth habit, they can be arranged from the weakest growing, which create only a small tree more similar to a bush, to vigorously growing rootstocks that create a large tree.

By choosing a rootstock, you can determine how large the tree will be. It should be noted that weakly growing rootstocks require greater care (watering, hoeing), cannot tolerate grass growing right up to the trunk, and require support in the form of, for example, a stake throughout their life. On the other hand, they bear fruit soon after planting and can be maintained in low forms that are comfortably managed without using a ladder.

Very weakly growing rootstocks are J-TE-G and M27, suitable for containers and very small forms. Still with some inertia, the most propagated rootstock today is M9, which is, however, still too vigorous for fruit walls and dense plantings, and also anchors poorly in the soil. For a free-standing tree, it is too weak; in case of poor care, it doesn't grow at all. For free-standing trees with a low crown, probably the best rootstock is MM106, which already anchors well in the soil and creates a modest-sized tree that can be maintained entirely from the ground. For classic forms of old gardens – large trees – the most vigorously growing rootstock A2 is suitable.

Apple tree varieties are divided according to ripening time into summer, autumn, and winter varieties. Summer and autumn varieties have proper consumer properties already at harvest time; winter varieties ripen only after several weeks or months after harvest in storage facilities. There are thousands of apple varieties, but only a few dozen are available. Nevertheless, there are great differences among them. For planting in gardens, it is better to choose resistant varieties that require minimal spraying. Market varieties whose names we see in stores (Golden Delicious, Gala, Granny Smith) certainly do not belong to these.

More resistant summer varieties: Průsvitné letní, Mio, Ametyst

Autumn varieties: Nabella, Rubín

Winter varieties: Resista, Petra, Spartan, Matčino, Bohemia Gold, Topaz, Lipno

Czech breeding can boast a whole range of varieties that are tasty, hardy and accustomed to local climatic conditions.

A Few Notes on Training and Pruning

After planting an apple tree, formative pruning is necessary. Its goal is to create an open and strong crown.

In later years, we focus on fruitfulness and pruning should bring the tree into balance between growth and fruiting. This is important for an adequate supply of reasonably sized fruit. The measure of optimal pruning is annual growth, which should be 20-30cm long. If it is shorter, deeper pruning is required; if it is longer, pruning should be reduced.

The timing of pruning is important - apple trees can be pruned from the end of February (after the main frosts) until the end of August. So-called autumn pruning is a widespread mistake; it has no more positive effect on the tree than pruning during the mentioned period. On the contrary, fresh wounds do not heal before winter and freeze - they heal poorly.

We use exclusively sharp tools, cutting to create the smallest possible wounds and leaving no stubs. These are always a gateway for wood-rotting pathogens (tracheomycoses).

We treat larger wounds, ideally all of them, with tree wound sealant for easier healing.

If we prune before bud break, the pruning will have a stimulating effect, as nutrients travelling from the roots to the above-ground parts are directed into a smaller space and the remaining branches thus have more nutrition available - they grow more vigorously.

Conversely, if we prune during and after flowering, we remove branches that already contain stored nutrients and the tree will initially grow at approximately the same intensity as it would if it had not been pruned.

Protection Against Diseases and Pests

The most common apple diseases are scab and powdery mildew.

These diseases can be successfully prevented by appropriate variety selection (we have plenty of quality resistant varieties). If we have already planted a susceptible variety, this problem can be elegantly solved by grafting the trees. Microclimatic conditions of the location also play a significant role. An airy, sunny location with gentle air movement is more beneficial for the tree than a closed and shaded site.

Apple scab - Venturia inaequalis is an ascomycete fungus that overwinters on fallen apple leaves. In spring, under favourable conditions, the fungus infects the tree using ascospores. Early infection during flowering and shortly after is the most dangerous.

Chemical Protection

Rational chemical protection of trees is based on multiple applications of various fungicides. To save resources and protect nature, it's important to know that scab spreads in humid conditions. This means that chemical treatments are carried out at specified intervals, which can be extended during dry weather. Against scab, we use contact fungicides that act preventively and curative fungicides that can stop the disease if applied in time.

For the first treatment – when the buds of future flowers are pink – we use a contact fungicide. This is followed by sprays with curative fungicide at intervals of approximately 14 days, depending on the weather. Currently, various spray sets are available that include an immunization schedule in their package information, eliminating the need to study the disease problem in detail.

Apple Powdery Mildew – Podosphaera leucotricha is another fungal disease attacking susceptible varieties in favorable locations. It manifests as grayish coatings on leaves and shoots, locally attacking parts of shoots. In neglected plantings of susceptible varieties (Jonathan), infestation can be significant. Nitrogen over-fertilization also has a positive effect on disease outbreak.

In young trees, removing affected parts of the tree has a major impact. Currently, most fungicides effective against scab are also effective against powdery mildew.

Apple Pests

The most serious apple pest is the Codling Moth – Cydia pomonella, which causes wormy fruit. The caterpillar overwinters in a cocoon in bark crevices and in the soil. Codling moths hatch in May and after mating, females lay 80-120 eggs. From these, caterpillars hatch, which after brief surface feeding, burrow into the fruit. After 4 weeks, the caterpillars descend from the fruit on a thread to the ground, or crawl along branches to suitable hiding places in the tree crown. Codling moths have 1-3 generations per year in our region. The fruit later reacts to infestation in most cases by dropping, which may be preceded by secondary infection with botrytis. Later infested fruits ripen prematurely and are edible but quickly deteriorate. In years of codling moth outbreaks, up to 80% of fruits may be infested.

Overwintering caterpillars in bark crevices are eliminated by tits, and scratching poultry eliminates some from the soil if they have access. This can eliminate up to 90% of caterpillars after winter. Codling moth eggs are also sought-after food for earwigs, which can eliminate 40% of them. Supporting natural enemies is therefore appropriate.

In large orchards, pheromones are used against codling moths – substances that confuse male codling moths so they cannot find females. Other means against codling moths are biological preparations based on codling moth granulovirus. The availability and use of these methods on a gardening scale is not justified.

Chemical Protection

Insecticides are used against codling moths, preferably selective ones that don't kill a wide range of insects.

Our tip: apples in a dressing gown - apples wrapped in puff pastry :-)