Stechpalmen (Ilex), also winterberries called, are evergreen or deciduous deciduous shrubs and form the family of the Stechpalmengewächse (Aquifoliaceae) as single type. About 400 species belong to the plant genus Ilex worldwide. Characteristic for hollies are their leathery, dark green leaves, which are often thorny toothed, and the mostly bright red stone fruits. Holly is common in all climate zones worldwide, in China alone there are over 200 different species. The common holly (Ilex aquifolium) is at home in Western Europe and has its natural habitat in coniferous and deciduous forests with rather acid, humus-rich soil. It is most widespread in the winter mild North German Plain, mainly in Lower Saxony and Schleswig-Holstein.
Holly twigs with fruit on them have a long tradition as Christmas decorations in England and America. However, leaves and fruits are highly poisonous, so care must be taken when handling plants when children are in the garden. The heavy, greenish wood of the Ilex used to be popular for inlaid furniture. It is also used to make woodcut printing blocks and walking sticks or magic wands. Of course, Harry Potter’s magic wand is also made of holly wood.
Appearance and growth
Depending on the species, holly can grow to a height of 2 to 25 metres and can be several hundred years old. Depending on the species, they grow tree-shaped or as small, broad-bosomed shrubs. On the often somewhat confused long shoots, the stem leaves are arranged alternately – this is an important distinguishing feature, for example, in the small-leaved garden forms of the Japanese holly (Ilex crenata), from the very similar box tree, which bears opposite leaves. The dark green, leathery leaves are stalked and mostly elliptical in shape. All Ilex species are dioecious, i.e. there are plants that have only male flowers and plants that have only female flowers. The small white flowers are located in the leaf axils of last year’s shoots and open in May and June. The pea-sized yellow, red, brown or black stone fruits contain one to ten seeds depending on the species and often remain on the plants until spring.
Location and soil
Holly want a bright, but sunny to shady location with fresh to moist, nutrient-rich soil. They grow optimally on acid, permeable humus soils. However, they do not tolerate clay soils rich in lime.
Planting and care
All holly, including the deciduous species Ilex verticillata, should be planted in spring after the strongest frosts have subsided. So the plants have a whole season to grow in and are well prepared for the first winter. The location should not be fully sunny, because then the evergreen species often suffer from frost dryness during strong sunlight and sub-zero temperatures. Individual leaves or whole branch parts freeze to death because the warming sun stimulates the evaporation of the leaves, but water cannot be supplied through the frozen pathways in the wood. Very loamy soils should be emaciated extensively with sand and deciduous humus before planting, because hollies do not like dense, cohesive soils. If you want to plant a hedge, you should lay out the individual plants at the required distance along a continuous planting trench. Depending on the type and size of the plants, two to six specimens are required per metre.
The generally quite undemanding hollies do not need any special care. In spring, the plants are fertilized with a low-calcification rhododendron fertilizer or deciduous compost mixed with horn semolina. Sensitive varieties should be protected from frost damage with winter fleece in open, windy locations. In addition, the forest dwellers feel very comfortable with a mulch layer of bark humus.
Stechpalmen are very cut-tolerant and also taper out of the old wood. The plants can be pruned at any time if required, but the best time for pruning is early spring or late June. If you use holly as a hedge or shrub, you should not cut large-leaved species such as Ilex aquifolium or Hybrid Ilex (Ilex x meservae) with motorised hedge trimmers. A mechanical hand-held hedge trimmer is better suited because the leaves do not fray so much during cutting and do not show any cut wounds that have dried up over large areas.
Stechpalmen are ideal as shrubs and for hedges. In exposed locations, the more robust hybrid Ilex varieties (Ilex x meservae) are particularly recommended, as they do not suffer from leaf damage so quickly in frosty temperatures and winter sun. All Ilex varieties can also be used as underplanting for other, larger woody plants, as they get by with relatively little light. Holly is well suited for Asian gardens with many other evergreens. The compact varieties of Japan Ilex are also well suited as solitary shrubs in tubs, and varieties such as Green Lustre are often recommended as substitutes for disease- and pest-affected boxwood borders. It should be noted, however, that they are far less adaptable to different soil types. In any case, you need an evenly moist, very humus-rich and acid soil in order to grow satisfactorily. Who expects fruit jewellery, should always set both a female and a male Ilex. Stechpalmen are also good bird-nut and brood-shrubs. The flowers are often visited by bees and bumble bees.
Species and varieties
From the genus Ilex, there are three species or hybrids, which are of greater importance to us as gardeners. The common holly (Ilex aquifolium) is an evergreen, mostly multi-stem large shrub or tree, which can grow up to seven meters high. In addition to the already mentioned green-leaved wild species there are numerous colorful-leaved breeds such as ‘Argentea Marginata’. The Japanese or mountain holly, also known as Japanese holly (Ilex crenata), is a diverse shrub that reaches a height of about two to three metres as a game species. The varieties cultivated for the garden remain much more compact with a height of 60 to 150 centimetres. Its evergreen leaves are small and oval and not spined. The shrub is very well tolerated for cutting and is easy to shape. Flowers and fruits are rather inconspicuous. Attractive varieties are, for example, ‘Golden Gem’, which grows about 60 to 80 centimetres high and has yellow foliage. Convexa’ shows characteristically downward arched leaf margins.
The bushy holly (Ilex meserveae) is not a species of its own, but originated from a crossing of the native holly with an East Siberian holly species. The upright conical Ilex hybrids can grow to 1.5 to 3 metres high and are very hardy. The variety ‘Heckenfee’ is female and should always be planted together with the male variety ‘Heckenstar’ if you want to decorate your garden with fruit. The deciduous holly (Ilex verticillata), also called red winter berry, is rather rare in our gardens. The deciduous shrub, which originates from North America, grows to a height of around 3 metres and bears its striking red fruits long after the deciduous fall in autumn. The autumn colouring of the leaves is yellow to orange.
Larger varieties of the native holly (Ilex aquifolium) can easily be propagated as a hobby gardener by lowering, as the long, whip-like shoots in the lower crown area often lie on the ground anyway. In the nursery, Ilex varieties are almost exclusively propagated by cuttings. However, the rooting process is quite lengthy and requires a certain amount of ground heat. In the hobby garden, this can usually only be achieved with special growing stations or mini greenhouses in which floor heating is integrated. The sowing of wild species is very lengthy and less recommendable. The seeds show a strong sprout inhibition, which must be removed by stratification first.
Diseases and pests
The holly is relatively frequently attacked by the Ilex miner fly, whose small larvae live in the leaf tissue, leaving behind light to brownish miners. They also pupate themselves in the leaves. Infested leaves should therefore be carefully removed in early spring and disposed of in household waste before the new generation of flies hatch. Also Dickmaulrüssler eat occasionally at the fleshy Ilex-leaves. They are easy to identify by their characteristic bight feeding along the edges of the leaves and can be fought well with nematodes.
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