At first glance, it might sound a bit strange when we talk about cutting and freezing some of our young plants after they have grown successfully and finished maturity. But this is a cultivation activity that not only benefits us as a producer. Above all, you as our customer benefit from this measure. Read below in the following text why it is worthwhile to buy the overwintered young plant quality. Incidentally, in our availability list and in videos, we also call the overwintered young plants “2-year-old young plants” as they have been fully cultivated in the previous year, then frozen and finally sold from February to May of the following year (the second year) and then potted by producers of finished plants.
The assortment of overwintered young plants
Unlike the spring-propagated quality, we can basically offer our entire assortment as an overwintered/ two-year-old quality. However some raspberry varieties are only available as overwintered young plants. This is due to the fact that the corresponding varieties as early-propagated young plants cannot produce sufficient quality for us and for you in the short time. The Phytophthora-resistant summer raspberry ‘Sanibelle’, for example, stops too early during the potting of spring-propagated young plants; but if you use overwintered young plants, we can guarantee a problem-free production of 12 cm pots up to 3 L containers. It goes without saying that we offer such a variety exclusively in the overwintered quality.
Production and availability of the overwintered young plants
Picture: raspberry young plants in summer for overwintering
Depending on the individual crops, we start with the production of the overwintered young plants around mid-June. The last batches for the overwintered young plants are pricked out no later than the beginning to mid-September. In these late sets, however, the management of the crop must be adapted so that a good rooting of the individual tray cells is also guaranteed.
A big exception in the range of overwintered young plants is the Vaccinium species. This is because there is a much longer lead time. The actual micropropagation takes place between August and October. The pricking out into the standard tray takes place during the first two months of the following year. This happens so early, so that both natural growth spurts of the blueberries can be taken advantage of to the full extent. In doing so, the plants can be cut back at least once.
After the production has been successful with good rooting and robust plants, the young plants are allowed to mature naturally and lose their leaves. After the plants shed their leaves, the individual plant groups are cut back accordingly and stored/frozen where applicable.
Thus, it can be seen that even a short-term increase in the number of overwintered young plants is not possible. After all, the actual production of the young plants is preceded by the production planning of the micropropagation. Even marginal volume increases can only be successfully implemented with a certain lead time. It is worthwhile in any case, if you inform us about an additional need for overwintered young plants early. When it comes to larger quantities or new production batches, a lead time of 9-12 months before the planned delivery makes sense.
Picture: stacked trays for freezing
The freezing of the young plants takes place mainly with raspberries, blackberries and rhubarb. These are crops that are cut back so much that they can be stacked or all of the aboveground plant parts die back and only the storage roots in the tray cells remain for overwintering.
For raspberries, the plants are cut back after they have completely lost their leaves, which is usually the case from mid to late November. The blackberries are cut back from the beginning of February before the plants start growing again due to the longer days. Since blackberry plants usually stay green during the winter, the active leaves are removed during the pruning process. This is completely unproblematic and rather advantageous, since no evaporation surface is left.
After pruning, the trays are checked for completeness and adjusted if necessary. Thereafter, the trays are watered so that all of the plants have the same humidity. After this watering process and a short drying phase, the individual trays are stacked on a CC® container/trolley in offset. This offset positioning is important so that the plants in the lower trays will not get crushed. Then the trolleys with the stacked trays are frozen in our cold storage at -1.0 to -2.0°C. At this temperature, there is no damage to the plants and because of the way they are stacked they are also protected against dehydration.
Picture: CC container ready for delivery
This type of storage is nothing more than an artificial extension of winter. Thus, we always have the opportunity to get the young plants, in this frozen state, anytime from the cold storage and deliver them directly. Our experience has shown that it is possible to deliver the frozen young plants in this condition without loss of quality until about mid-May.
So please do not be frightened if you get young plants from us in an already advanced spring, but there is no fresh green to be seen. You can be sure that the plants will develop optimally.
Use and possible applications
Picture: production of raspberry plants
The overwintered young plant quality refers to young plants that have matured naturally, the leaves have fallen off and they have been hardened off well. We deliver these young plants in early spring when they are still dormant. We can guarantee this quality thanks to the storage and freezing processes described above. As a result, we are significantly more flexible in the delivery and even at a later delivery date, we are much more independent of the weather. But it is not only us that have advantages such as free greenhouses for the subsequent production. Especially you as our customer can benefit very clearly from this quality. By freezing, the effect of cold on all young plants is the same, as it ensures a very even new growth. In addition, the plants are still much less sensitive to the new site conditions after delivery, since there is no new growth. But the biggest advantage you will have with the overwintered young plant quality is the independence from the weather when potting. Due to the good hardening of the young plants and the artificial extension of the winter, the overwintered young plants can be potted outdoors directly, since there are no hardening problems whatsoever. This allows the plants to develop directly where they were potted with the seasonal weather progressing and thus get used to the direct sunlight.
A summary of the advantages and disadvantages of the overwintered young plant quality (2-year-old young plants)
Let's start with the benefits of 2-year-old, overwintered young plants:
- They are usually more robust and slightly stronger than 1-year-old young plants
- Early availability starting in February
- Independent of the weather during the pot life
- Sufficient coldness, resulting in very regular sprouting and start of growth
Of course, the 2-year-old overwintered young plants also have disadvantages; otherwise our customers would only order such young plants. ;-)
The main disadvantages of overwintered young plants compared to 1-year-old, green young plants are the following:
- They are available only until May; only 1-year-old, green young plants are possible for later potting
- Planning is inflexible because the plants must be planned and ordered very early, due to the long lead time of about one year
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