Boscs Flaschenbirne lives up to the name 'Kaiserkrone', which is also used, and is a very valuable, old variety in the home garden. We'll tell you why.
'Boscs Flaschenpear' is also known under the names 'Kaiser Alexander', 'Alexanderbirne', 'Beurré d'Apremont' or 'Kaiserkrone'. This type of pear still bears a lot of fruit even when it is old and is best suited for direct consumption due to the sweet, tenderly melting fruit flesh and the limited shelf life.
Boscs Flaschenbirne: Wanted Poster
| Synonyms | 'Kaiser Alexander', 'Alexander pear', 'Beurré d'Apremont', 'Kaiserkrone' |
| Fruit | Medium-sized to large, green-yellow skin with heavy yellow-brown russeting |
| Flavour | Sweet, very juicy |
| Yield | Regular, medium to high |
| Harvest time | From mid-September |
| Maturity for pleasure | From October |
| Shelf Life | Storage in a cool place until December/early January |
| Growth | Medium strong, pyramidal crown |
| Climate | Widely cultivable, also suitable for medium altitudes |
| Diseases and Pests | Susceptible to local scab, moderately susceptible to viral stone fruit |
Origin and History
Where 'Bosc's Flaschenbirne' (Pyrus communis 'Bosc's Flaschenbirne') has its origin is not exactly clear. However, it is assumed that it originated as a chance seedling in Belgium or France at the beginning of the 19th century. Your name goes back to the director of the botanical garden in Paris Bosc. It is said to have found its way to Germany under the name 'Kaiser Alexander' pear by the pomologist Van Diel in 1810.
Tip: The name 'Kaiserkrone' used synonymously is also used for the pear variety 'Prinzessin Marianne', which, however, ripens earlier and has a significantly different tastehaving. Despite the similar appearance, these are not the same variety of pears.
Properties and taste of the ‘Kaiser Alexander’ pear
The shape of the medium-sized to large fruits can best be described as cup-bellied or bottle-shaped. They tend to get slimmer towards the stem. This is sessile, sometimes with a small bulge of flesh. The basic color of the 'Bosc Flaschenbirne' is actually green-yellow - but this is usually not visible at first glance, since the yellow-brown russeting of the shell is very dominant. This is typically washed out and net-like. The shell is rather rough and dry, but this does not bother when eating. In contrast, the whitish-yellowish flesh is not dry at all, but very juicy, sweet and very tasty.
Cultivation and care of the pear tree: This is important to note
The 'Kaiserkrone' pear variety can cope with many different growing conditions, so it can be cultivated widely and can even be grown at medium altitudes. It prefers warm and nutrient-rich soils that should not be too moist or clayey. Sandy, loamy or humus-rich substrates are ideal. If there is too much copper or sulfur in the soil, the tree can react somewhat sensitively.
The tree of the pear variety 'Kaiserkrone' grows medium strong with a pyramidal crown. It requires yearly pruning, during which old branches should be removed and overhanging fruit branches should be diverted to more upright side shoots. 'Bosc Flaschenbirne' forms long fruit shoots and branches poorly. For this reason, the tree should be pruned several times in the first few years during the training pruning so that sufficient skeletal branches are formed. Old, rarely cut trees of the 'Boscs Flaschenbirne' variety often only consist of inferior, hanging fruit wood and then have to be rejuvenated more radically. For general tips on how to properly prune your fruit trees, see our special article.
The pear is offered as a standard, half-stem or bush tree. 'Boscs Flaschenbirne' is also very popular in the trellis, although its growth behavior is not ideal for this. Quinces are unsuitable as a base for this pear. The use of the rootstock quince A is possible with intermediate grafting. For taller trees, 'Gellert's Butter Pear' is recommended as a stem builder. The weak-growing rootstock 'Pyrodwarf' can be used for half-stems or bush treesbecome.
The 'Kaiserkrone' pear is only locally susceptible to scab and only moderately susceptible to viral stone fruit, which offers an advantage over varieties such as 'Gellert's butter pear'. The wood of the tree is sensitive to frost, but the flowers are usually sufficiently resistant to late frosts. Even when using plant protection products, no agents with a lot of copper or sulfur should be used, as the 'crown imperial' is sensitive to them.
The flowering time of 'Bosc's Flaschenbirne' is between April and May. For example, the 'Conference' variety, the 'Williams Christbirne' or 'Clapps Liebling' come into question as pollinators for 'Boscs Flaschenbirne'. If you combine these in your garden, the varieties can pollinate each other as the 'Alexander Pear' is a good pollinator.
You can also expect a good medium to high yield from this strain, always very regular and mostly of good quality.
Tip: With a primarily organic complete fertilizer such as our Plantura organic universal fertilizer, the low sulfur content of only 2% is ideal for this sensitive variety. At the same time, the organic fertilizer with its long-term effect offers the advantage that you don't have to constantly re-fertilize your pear tree, even if you cultivate it in pots.
Harvest and use Bosc's Bottle Pear
The 'Kaiserkrone' pear can be picked from mid-September and is ready to eat from October. It is advisable to pick them when they are hard, as the fruit can easily fall off when they are really ripe. If the pears are stored in a cool place, you will still have some of your pears until December or early January, as they can be stored at 0°C for two to four months. The large fruits are best suited for direct consumption or processed as a compote or for drying. They are less suitable for pickling, as the pear turns brown in the glass.
In our special article we explain in more detail how to plant your young pear tree.