This article discusses the nursing of plants, which means taking care for plants from when they are seed to when they a few months-1 year old and the period of acclimating plants to the cold weather (the period in which you put the plant outside a few hours per day and build this up untill they can be permanently placed outside[1]). Besides discussing the acclimating process, we also discuss in this article the action of tranferring plants (moving plants in larger pots as they grow up).

Sheltered nursing[edit | edit source]

Nursing from seed[edit | edit source]

Sowing plot For a good emergence of the sown seeds, a good sowing soil is needed. On such a sowing soil, we place the following requirements:

  • it must be able to hold enough air
  • it must be airy
  • it must be as fine as possible so that the seed can be dispersed finely and a so that there is a good contact with the soil in order to germinate
  • it must be disease free
  • it must be nutrient-poor

Sowing soil is usually a mixture of tuinmolm, peat and sand. In the shop, good sowing soil can be purchased.

Place of sowing - not on site This means that the plants are to be moved one or more times. Possibilities are: A. Sowing in containers As a seed box, we take styrofoam boxes with a 6-8 cm depth. We fill the box halfway with sowing soil and we gently press the edges with a board. The remaining soil is now sifted into the box unto 2 cm below the edge, and the edge is gently pushed, this causes them to dry out less quickly. The soil surface needs to be made smooth pressing it. The seeds should be equally distributed over the entire box. Seeds that gather up into a pile are too close to each other and have more chance of fungal attack. The finer the seed, the closer they can be together and the larger the seed, the farther apart. The seed is divide into 2 portions. We sown with the bag or with a folded paper. We place the forefinger inside the folded piece of paper and hold it down with thumb and middle finger. Sprinkle in a reciprocating motion, as smooth and as thin as possible, into the seed box. Turn the box sideways and repeat with the other portion of the seeds. Very fine seeds is best mixed with dry silver sand for better dispersal. We introduce a covering layer (sowing soil mixed with sharp sand) with a the thickness equal to the seed. The newly sown boxes are watered with a fine spraying. In order to prevent the moisture needed for the germination of evaporating, the box will be covered with a glass or put under plastic. Through the evaporation, drops will hang from the glass that will fall on the soil, possibly causing fungi to spawn. Therefore, the glass plate will be turned if too many drops adhere to it. In the beginning, we place a newspaper over the glass. Most plants are dark germinators. The newspaper prevents the young seedlings of burning by the sun. Once the plants have germinated, we remove the glass plate.

B. In flower pots or press pots If plants are inmediatelly sown in flower pots or press pots, the cultivation takes less time. In the beginning however, you need more room. On can introduce the seeds in several ways:

  • By laying out coarse seeds
  • By driving fine seed with a nail into the soil, there are then several seeds per pot

Professional cultivators grow many herbs in pots. So as to be able to keep the plants in a pot a long time, nutrients need to be administered (sowing soil=nutrient poor). These are usually given along with the water.

C. Sowing in trays or multi plates This are polystyrene plates that are divided into a large number of boxes or cells. In each box, a seed is introduced. The sowing is done mechanically. Each plant is grown individually and thus forms a plant ball, hence the name balled plants. Advantages are:

  • Diseases can difficultly spread
  • The transplanting of the plants is 2X as fast
  • No transplanting shock since no root fracturing occurs

After the sowing, they are placed in germinating cells where there is an optimum relative humidity and temperatures.

Transplanting This is the transplanting of the young plants from a seed box, at the time when they are still small and have little roots. Transplanting can be done in:

  • Boxes
  • Press pots or flower pots
  • Open-field (full soil)

Some plants are already transplanted in the germ leaf stage, others are transplanted with the inset of the 1st or 2nd true leaf. When transplanting in boxes, we fill a box similar to sowing. The young plants are taken out of the seed box by lifting the plants with a small transplanting board. We start in a corner of the seed box. Pick up the plant by placing the leaf (without touching the stem) between thumb and forefinger of one hand. We make a hole with the transplanting board, and the plant is placed sufficienctly deep (up to the leaf) in the hole. We start transplanting from the middle of the box and work the row from left to right. We then rotate the box and finish the rest.

When transplanting in press pots, the plants are placed in the center of the cleared space. Make sure that the roots wind up in the hole of press pot. With the fingers of the other hand we gently press from the outside inwards. Press pots have the disadvantage that they easily dry out and harden making them difficultly rootable and slowing down the growth.

When transplanting into pots, we scoop the jar full with soil and make a hole in the center of the soil in the pot with the finger. We place the plant inside the hole and press the soil with thumbs and forefingers. The transplanted plants are watered to prevent wilting. After the transplanting, the plants are not put in full sun so that they can quickly start to grow.

Nursing of clones[edit | edit source]

A clone is a a new plant formed from large or small parts of the parent plant. After the action of making a new plant, we need to grow them up. Note that young plants (ie cuttings, ...) need to be separated from the older ones, older plants are more prone to virusses, and will then transfer them.

Potting[edit | edit source]

Potting is placing a well rooted plant in a pot. This can be cuttings that have sufficiently rooted, divisioned plants, ... The potting soil that we use here must contain sufficient nutrients. When potting plants that have few roots, we proceed similar to transplanting into a pot. When potting plants with a good root wig, we work as follows: We take the pot in one hand and hold him with 2 fingers. We hereby scoop soil into the pot. With the hand, we press the soil that is present in the pot to the back. After this, we take a plant and keep it at the right height inside the pot, the roots are held on the side of the pressed soil. With the other hand, we fill the pot with potting soil. Then, we press the soil with both thumbs. The pressing of the soil is important. The more we compress the soil, the slower the growth. The plant will then be stronger, but the growth is slowed. Try to minimize the damaging of roots when hoarding. The less damage, the faster the plant will grow.

Climate with sheltered nursing[edit | edit source]

Light[edit | edit source]

Why light? Light is the most important growth factor, as an energy source to connect the carbon dioxide from the air and the water from the soil to carbohydrates. Light means plant activity = evaporation. Light dependant ! Light is thus the limiting factor in growth. Especially in periods of low light, this must be taken into account. Low light with high temperatures in the greenhouse gives elongated, weak plants. In the winter months, we will thus regulate the temperature depending on the light.

  • With sunny days, we turn the temperature up
  • With dark days, we turn the temperature down

To get an optimal light entry in the low-light winter months, we will make sure the glass is clean (glass is washed at interior and exterior, dirty glass can give up to 30% light loss). In winter; to use the little light of the wintersun, the greenhouse is best oriented with the long axis from east to west. In winter, the arc between the points of rising and falling is 60 meters, and 120 meters in summer. In winter, only the south of greenhouse gets direct sunlight. In the summer, the ends also get sunlight in mornings and evenings.

Temperature[edit | edit source]

Because of the greenhouse effect, the temperature in the greenhouse will increase with sufficient light radiation. Light reaches the Earth as short-wave radiation, which easily penetrates glass and plastic film. These rays heat everything they touch, such as soil, plants, pots, tablets, ... These will redirect a part of that heat back as long waves. Because glass blocks these long waves, the result is a large increase in heat in the greenhouse. When radiation passes through plastic fil, it is diffuse and the reflected long-wave rays are not blocked by the foil. Plastic greenhouse's thus also cool down a lot faster than glass greenhouses. Direct sunlight must be able to hit the glass at an angle of 90 m, if the maximum amount of sunlight needs to be entered. If the angle is greater or smaller, a part of the sunlight will be reflected. The sunlight reaches the earth in winter at an angle of about 15 m. At dark days, this means little light and therefore low temperatures. At sunny days, this means higher temperatures.

With cold greenhouses (unheated), the temperature will have great fluctuations in spring. With frost, the greenhouse temperature will fall below the point of freezing. To prevent damage to the crop, we can additionally cover the plants with foil or fleece. A cold greenhouse or a cold tunnel greenhouse is then used for the winter cultivation of energy-poor leafy crops, for taking cuttings in spring and autumn, for a cold cultivation, to hibernate sensitive plants in winter. With hot greenhouses we will, by means of a heating element, be able to control the temperature in the greenhouse and thus prevent large fluctuations. For this, we make use of tube heatening (heater circuit with circulation pump and piping in the greenhouse) or a CO2-burner. Depending on the crop, we will make use of:

  • Soil heating: applied with container beds and seed beds
  • Tablet heating: applied with seed and cuttings tablets
  • Space heating

Depending on the crop, a minimum night and a minimum daytime temperature are set. The heating is always done with closed windows or a closed ventilation system in order to prevent energy loss. Heating has an impact, not only on the temperature, but also on the RH (relative humidity). The warmer, the more water vapor the air can contain. With a temperature increase, the RH will decrease the. This is a technique often used in dry firing.

Ventilating[edit | edit source]

Why ventilate[edit | edit source]

  • Because of the temperature regulation: Taking into account the amount of available light, every crop has a maximum temperature. Above this temperature the plant will exhibit negative symptoms. When these is exhibited, the greenhouse will need to be ventilation.
  • To refresh the air: The carbon dioxide content must be maintained. In a closed-off greenhouse, this is impossible. The composition of the air is 78% nitrogen gas, 21% oxygen gas and 1% other gases, including 0.03% CO2. Given that plant consumes, with a strong activity, a lot of CO2, a shortage will soon emerge that prevents growth. Professional cultivators are will increase the CO2 concentration heavily with a strong solar radiation in order to speed up the assimilation (eg in leafy vegetables). This can be through the use of CO2 -burners.
  • For the regulation the air humidity. The amount of water vapor that the air contains varies between 2 and 30 gram/m³. When the air contains too much water vapor, this will prevent the evaporation of the plant promote the occurring of diseases. By ventilating, a part of the water vapor leaves the greenhouse, together with the hot air. A good relative humidity is RH = 70%.
  • To harden off the plants. Plants that are nursed sheltered and are then planted outside should first be prepared on the outside conditions before that they are planted there.

How to ventilate[edit | edit source]

  • Through the roof: warm air rises. 1 m³ of dry air of 0°C and with a pressure of 1 bar weighs about 1,300 grams. If this air is heated to 30°C, the air expands. 1 m³ of this air weighs only 1180 grams, or 120 grams less. This causes convection currents, the warm air cools at the greenhouse roof, falls back down and the hot air rises.
  • The side sheltered from the wind: This is the side of the greenhouse opposing the wind. Beware of east winds (dries too much).

When to ventilate[edit | edit source]

  • At daytime: depending on the temperature and the amount of light in winter at a sunny day, the temperature in the greenhouse can be higher, the windows are then kept closed in the morning, so that the temperature will rise due to the greenhouse effect. With a cloudy day, the temperature should not be so high in the greenhouse, and more ventilating can be done.
  • In the evening: after a sunny spring day, the windows will be closed earlier so that the greenhouse can not cool off too strongly and so that the night-day temperatures do not differ too much. After a cloudy day, the windows will be closed late or even not at all. The plant then comes more quickly to rest.
  • In the morning: avoid sudden temperature changes

Shuttering[edit | edit source]

Why shuttering[edit | edit source]

  • As a sun covering to reduce the temperature when ventilating is not sufficient.
  • For protect seedlings, transplants and recently cut plants from drying out and to promote regrowth.
  • To slow down the quickly increasing evaporation with sudden weather transitions from a dark period to a sunny period in spring.
  • In winter as an energy conservation (energy shutter)

Sun shutters[edit | edit source]

In a non-shuttered greenhouse, the leaf temperature is up to 15°C higher than the air temperature. If the leaf temperature gets too high, the leaf will be burned. A shutter reduces the radiation and thus the leaf temperature to a few degrees above the air temperature. The air temperature can be kept, through a a good shuttering and ventilation, to a few degrees above the air temperature. Too dense shutters (films), can inhibit the evaporation of the plant, which has a slowing effect on the leaf cooling and the leaf temperature rises again possibly causing the plant to be burned.

How to shutter[edit | edit source]

  • Persistent: chalk, chalk white. The more is dissolved per liter of water, the denser the shutter. Apply using a brush, smear or sprinkle. Calcium shutters halve the sun intensity. In dark summer days, this has large drawbacks. These shutters are removed in autumn.
  • Temporary shutters: shutter cloths made of:
    • Fiber (polyester) and acrylic cloth (not vapor-tight)
    • Foils (vapor-tight)

These shutters are movable in the greenhouse and can be pulled open and closed as needed. Eg in the form of a:

  • Slidable shutter
  • Rollable shutter
  • Foldable shutter

Watering[edit | edit source]

Why watering[edit | edit source]

  • Water is a means of transport, temperature regulation, nutrient (needed for sugar formation) and it also keeps the plant firmly upright.
  • For the soil, water is necessary as a temperature regulator and to maintain the soil structure (too much can damage it)
  • For the fertilizer substances in order to dissolve

How to water[edit | edit source]

  • Spraying: on seed beds, cutting beds, ... with a fine sprayer
  • By watering can: Rose pointed upwards, heaviest water impact next to the seedbed
  • By garden hose: fine drop, water in a big arc so that it warms up and lands gently.
  • By rain pipe: PVC pipes that are suspended at the roof of the greenhouse. 1 pipe per 3,20 caps, spraying caps at 1.5 meters.

As a spray head, we use ricochet caps:

  • bar cap
  • sphere cap

The caps are pointed upwards, but so that they do not spray the walls or roof.

When to water[edit | edit source]

  • Always in the morning so that the plants are dried up at night.
  • In sunny and drying weather, th plants than require the moisture and have a chance to dry. A wet plant that can not dry up also can not evaporate, so that there is no supply from the roots and thus no growth. A plant that is left wet too long is also an ideal target for a fungal attack.
  • With very hot weather, watering is done in the evening
  • Avoid giving the plants get a cold watering and that the crumb structure of the soil gets damaged.

How much water[edit | edit source]

This is depending on the crop type, weather, crop size, soil type, season. In winter, we give water in short shifts to leafy vegetables to not too wetten the plant and soil too much. A few minutes, every few days, depending on the weather. In summer, we give gifts of 5-10 minutes. A light soil color means water shortage. Soil of 10-20 cm deep is squeezed and dropped using one hand: it should not fall apart, otherwise it is too dry. A plant with a bright color and less shiny leaves that also falls over at night requires water.

Flushing[edit | edit source]

In greenhouses where there is no natural precipitation, the upper soil layer will salinate through the use of organic and chemical fertilizers. After all, we give just enough water for the plant and soil water will rise further causing salts to get stuck in the upper layer. Therefore, after a summer cultivation, the soil in the greenhouse will always be need to be flushed. This is done by watering in shifts of 15-30 minutes, separated by an equally large break, and this for several hours. The present salts are then washed out downwards and discharged through the drainage pipe.

Transplanting the plant to the outside[edit | edit source]

Plants cultivated in pots, press pots or sowing boxes have large root systems. For this, the planting holes are best made with a spade. Make the holes large enough for the roots and plant as deep as the pot or even somewhat deeper. Divisioned plants such as chives, mint or the rooted shoots of thyme are planted with bare root in the soil. We use for this a planting stick or planting shovel. Thyme, and mint are planted deep enough so that the bare stems are below the soil and roots too can be formed there. After the planting, the plants are repeatedly watered at regular intervals until the plants are well in growth.

Source[edit | edit source]

This article is made using information from the coursebook: Cultivation techniques
Part 5: Cultivation methods
Course from: 1st year of Herbalism
Course year: 2005 - 2006
Education center: Syntra, Asse-establisment
Teacher: Leo Van Crombrugge

Additional sources:

See also[edit | edit source]

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