Dahlias - Protection and Storage
In dry autumn weather, dahlia leaves suffer short-term frosts of -0.5 ° - -1 °. Only a slight darkening is observed. Dahlia stems tolerate short-term frosts up to -2 °. In the middle lane, the onset of the first frost occurs on average on September 8-17, and early frosts are often observed in early September. Sometimes by September 10 they reach -4, -6 °. At this temperature, not only leaves, buds and inflorescences die, but also the stems.
If the dahlia stems are affected, the roots, like powerful pumps, continue to supply juice with dissolved nutrients to the aerial part, and capillaries damaged by frost cannot supply them to the leaves, circulation is disturbed, the juice accumulated in the lower part of the stem begins to decompose, which leads to decay of the dahlia neck and the whole tuber. Therefore, with severe frost damage to the stems, it is urgently necessary to dig a dahlia.
Usually, after a short early autumn frost, the weather is still good for a long time, sometimes up to a month. Therefore, it is advisable to take all possible measures to protect plants from the first frosts. There are many ways with which you can protect dahlias from frost: sheltering plants, heating with bonfires, stoves, etc. But they are all very expensive, time-consuming, or unreliable. The most common method of dealing with frost - the smoke screen - often, especially in the wind, does not give the desired effect.
A simple and effective way to protect plants from frost is sprinkling, the protective effect of which is based in general on the following. Water in a water supply system or wells has a temperature not lower than + 6 ° and when it decreases by 1 ° 1 m3 water emits 1000 large calories of heat. Sprinkling itself increases air humidity, which, in turn, reduces heat radiation from the soil and plant. At the same time, moistened soil, due to an increase in thermal conductivity, transfers heat to the surface air layer. The water that settles on the surface of the plants freezes, gradually dressing it with a very thin, but dense ice crust. The temperature under such an ice shell does not fall below -0.5 °. Ice saves the plant from frost. During thawing, evaporation is slower and is accompanied by heat absorption. This contributes to the slow melting of ice in the intercellular spaces and the absorption of water from them by the protoplasm of cells.
In the fall of 1959, the following experiments were carried out in the Main Botanical Garden: a sprinkler was equipped at the dahlia site. During the growing season, it was used for irrigation, during frosts - to protect plants by sprinkling. Water was sprayed with nozzles with a range of 3.5–4 m. The nebulizers were connected with a soft hose to the water supply network and installed at a distance of 8 m from each other along the midline of each workstation at a height of 1.5 m. Sprinkling started at 0 ° and continued until until the temperature rose above 0 °. At an air temperature of -4 ° C the plants were covered with a layer of ice.
Measurements showed that the air temperature in the sprinkling area was always 2 ° higher than in non-irrigated areas.
Despite the fact that the air temperature dropped to -6 ° C on September 28, the dahlias in the sprinkling area after thawing were intact, while the control plants died.
The milder frosts of September 30 and October 3 did not even cause the formation of an ice crust, although the temperature in the air over an unprotected area reached -3 °. Prior to the establishment of stable night-time negative temperatures from these plants, good inflorescences were cut. Analysis carried out after digging up the tubers showed that the plants protected by sprinkling in the 12 days after the first freezing gave a significant increase in the weight of the tubers compared to the control.
The sprinkling method lengthens the growing season of plants in open ground. It should be most widely used in floriculture.
Harvesting and storage of root tubers
Before the onset of large cold weather, when the first severe frosts beat most of the dahlia leaves, it is urgent to start digging the root tubers.
Usually they dig up in late September - early October in good weather at plus temperatures so that the root tubers can be well ventilated. Digging is best done before noon, as 3-4 hours before the evening they will dry out and by the evening will be ready for harvesting. To dig a dahlia, you need to have two digging good shovels or two garden forks, a hacksaw, a pruning shears for cutting stems and a knife for trimming garters. First, the stems are cut from several plants, for example from 2-3 rows, then the stakes are removed, the labels are removed. After this, the root tubers are dug out of the ground and labels are tied up. When digging, you must try not to damage the root tubers. To do this, retreating from the rest of the stem (hemp) by 15-25 cm, they dig a tuber root from all sides, carefully lift it, holding the stump, slightly remove the ground from above with a hand and carefully remove it. Do not lift and shake the tuber off the ground for a stump. This can damage the neck of the root tubers. Cracking of the neck at the junction with the root tub, as a rule, leads to the death of the root tub in winter.
On heavy clay lands, it is better to dig the tubers together with a garden pitchfork or two shovels from opposite sides, retreating from the hemp to the length of the tubers. With the help of garden forks or two shovels, the root tubers are vertically lifted upwards with a large lump of earth and carefully placed on an even place, slightly shaking off so that most of the earth spread around, the rest of the earth is shaken off with a light blow of a palm or a wooden stick in a stem (hemp). With weak tubers it is better not to shake the ground. When the root tubers are slightly weathered and the sections of the stems are slightly dried, they are immediately stored for storage with a lump of earth. If the root tubers are to be stored in a store with high humidity, the root tubers are dried more thoroughly.
Winter storage of the root dahlia is a responsible and serious period. In the culture, there are many old varieties of dahlias, forming beautiful large dense root tubers that can be stored in the winter in any conditions. However, the new hybrid dahlia varieties created recently by Russian and foreign breeders, which far surpass the old varieties in color and grace in the shape of inflorescences, are often inferior to the old varieties in resistance during storage. However, subject to certain storage rules, new varieties are well preserved.
The best regime for preserving root dahlia is a temperature of +3 - + 6 °. Particular attention should be paid to the humidity in the storage, which should be maintained within 60-75%. If possible, the dahlia should be ventilated by opening vents or by periodically turning on a portable or stationary fan. Periodic movement of air in the storage allows you to maintain its uniform humidity, which significantly prevents the development of fungal diseases.
Before laying the root tubers for winter storage, it is necessary to disinfect the storage in advance with fumigation of sulfur at the rate of 50 g of sulfur per 1 m3 volume of the room. During fumigation, the store should be closed, all openings are tightly plugged. After this, the storage is well whitened with a solution of bleach or freshly slaked lime.
It is necessary to lay the dahlia root tubs for storage in one or two rows on dry earth, sand or wooden racks.
During the winter period, at least once a month, dahlia root tubers should be examined and appropriate measures should be taken depending on the nature of the damage detected. The death of root tubers in winter can often be the result of poor ripening (with thickened planting or cultivation on moist, cold soil, especially in low places), as well as the negative effect of the first frosts on dahlias with uncooked root necks, from excessive top dressing, especially repeated top dressing with mineral fertilizers high in nitrogen. In plants that grow and bloom well, the tissues of the neck and tubers are loose, unripe. The root tubers of these plants are usually poorly preserved. The preservation of root tubers in winter also depends on climatic conditions - in a very dry or rainy summer tubers do not receive the necessary nutrients and do not have enough time to mature sufficiently; from the conditions of their excavation - in frosty weather, when snow begins to fall, or it is more difficult to dig in rainy weather, tubers are wet, heavy, easily break off and rot in storage. The safety of the root tubers also depends on the varietal characteristics of the plants.
Correctly considering all these factors, it is possible to achieve almost complete safety of all root dahlias.
Among amateurs and flower growers, many diverse techniques have been developed for preserving the root dahlia. This is natural, because each grower has his own special agricultural practices for growing plants, different soils, different climatic conditions, different storage conditions of root tubers. Therefore, there can be no general storage rules.
The oldest breeder A. A. Grushetsky, having no special storage, kept dahlia root tubers in room conditions at a temperature of +12 - + 20 °. Dug out root tubs, trying not to damage, he shook off the ground and laid out in a greenhouse. With open doors and window leaves for 5-6 days, he dried them well, then cut off all the small roots and last year's old uterine tubers, shortened the stems, leaving hemp 2-3 cm long from the neck. Sprinkled the places of cuts with lime-fluff or greased with lime gruel. Prior to laying for 1 week, it kept root tubers at a temperature of +20 - + 25 °. During this time, breaks and sections have time to become covered with a cork layer. Then I lined boxes of 80x50x60 cm with thick paper. He poured dry crushed earth to the bottom (layer 3 cm). After that, he began to lay down root tubers. Each row of root tubers, after laying on top, was covered with earth and on top the box was tightly covered with paper. In this package, dahlias were kept almost 100%.
Many lovers before laying the root tubers for winter storage process them in a solution of potassium permanganate. N. Grotto processed root tubers as follows. Root tubers dug from the ground immediately immersed in water for several hours (from 3 to 12 hours). Then, with a stream of water or a brush, he washed off adhering clay soil and cut off all thin roots. After that, they transferred them into a vessel with a solution of potassium permanganate so that the tubers were hollow immersed together with the left part of the stem. The solution should have a dark purple color. The tubers thus withstood from 0.5 to 2 hours. As a result, they should acquire a dark golden yellow or light brown color. Eyes and green sprouts, sometimes appearing in the fall, do not suffer from this, even if the color of the root tubers is reduced to dark brown. The tubers aged in the solution, without drying, were placed in the basement and, after 2-3 days, covered with slightly moist, clean sand. This method of preparing the root tubers for storage provided almost 100% preservation.
Amateur flower grower S. G. Valikov stores the dahlia root tubers in a semi-moist basement in sandboxes. He thoroughly dries up the dug root tubers, cleans them from the soil, then removes all the small roots, damaged and rotten roots. The stalk leaves no more than 8-10 cm from the root neck. He prepares boxes (usually wooden, thin-walled), dries them, covers the bottom and walls with a double layer of newsprint, and gently folds the root tubers. Then he sprinkles them with calcined river sand so that there is a small layer of sand on top of the tubers. He covers the boxes from above with paper and puts them in the basement, making one on top of the other in two rows. In this position, the dahlia root tubers persist until spring.
In winter, S. Valikov monthly makes a surface inspection of the boxes. When mold appears, he wipes the boxes with a dry cloth. In the same basement are stored potatoes, sauerkraut, cucumbers and other pickles. The air temperature in the basement ranges from +2 - + 6 °. The relative humidity in the storage should always be elevated, not lower than 70%. With this storage method, the annual waste for an 18-year period averaged 4% of the number of root tubers planted.
A lot of trouble and disappointment gives gardeners storage of root tubers grown from cuttings. The root tubers of cuttings of plants heavily fed with all kinds of liquid top dressing with a high nitrogen content are poorly stored. These plants grow wildly, bloom beautifully, but their root tubers form loose, weak, with a large number of small fragile roots. Such root tubers are best stored with a lump of earth, without shaking, slightly ventilating and drying in the fresh air during excavation. Then the tubers are placed in the basement, well ventilated by vents. If the earth spread around the root tubers and the tuber is weak, then after easy drying they are recommended to be folded in a box and covered with dry peat, earth or sand.
Especially valuable varieties of dahlias can be propagated and stored by the method of summer cuttings, rooting all shoots from pinching. Rooted cuttings planted in pots are exposed in a bright place. These plants remain green all winter. Of course, this way you can save only a small number of plants.
Cuttings of the summer cuttings (from June to August) grown in pots, with the onset of frost, are cleaned in a warm room, and, if possible, they try to extend the growing season. Then, around the end of October, the stalks of cuttings of plants are cut, and after drying, the pots with nodules are removed into the basement (storage).
S. Valikov conducted experiments on the conservation of nodules grown from plants of summer cuttings. As these experiments showed, the June grafting gives the normal formation of small but sufficiently matured and matured nodules that are well stored. He kept them in a semi-moist basement in boxes covered with dry lowland peat or sand. The safety of nodules was 75–85%.
In July, the nodules are much softer and smaller in size. He kept such nodules with stems 10–20 cm long, wrapped them in thick paper, put them in boxes and sprinkled them with peat on top. The safety of root tubers was 60–80%.
Sometimes during June and August cuttings in open ground, not nodules are formed, but thickenings (callus) and a mass of small roots, the so-called "beard". S. Valikov kept such specimens with stems 16-25 cm long in peat. He did not shake the ground from the dug plants, carefully removed the leaves, shortened the stalk, laid out each copy on paper with peat poured on it, and carefully wrapped it. The specimens prepared in this way were stacked in boxes that were peppered with peat. With this method, the preservation was about 50%, and during normal storage, or even simply covered with sand or peat, specimens with a "beard" were not completely preserved.