Most pot plants will grow adequately in the standard potting soil or potting mix that is available from nurseries and garden centers. It is important to buy the best quality potting soil that you can afford as the pot plant will derive much of its nourishment from this potting mix for a long time and its health with depend on the quality of the potting soil used in container gardening. The potting soil should be of the right texture for optimum root development. It should contain all the essential nutrients required for plant growth and should be able to hold enough water to sustain the pot plant over a number of days. It should also have adequate drainage.
Potting soil and/or potting mix can be purchased from reputable garden centers and nurseries. Or alternatively you can make your own potting mix. Following are the ingredients for potting soil:
- Seven parts (by volume) of good garden loam soil for nutrients.
- Three parts (by volume) of sieved, well-decomposed compost or peat moss for moisture retention and nutrients.
- Two parts (by volume) of well-rotted manure for nutrients.
- Two parts (by volume) of river sand for drainage.
For every three buckets (i.e. 10 liter size) of this potting soil mixture you should also add 125ml (a half cup) of bone meal or super-phosphate, 125ml of general fertilizer like Slow Release 3:1:5 as well as a level teaspoon of agricultural lime.
You need to prepare your garden pots prior to planting in them. This preparation involves washing out the pot. If the garden pots are made of porous materials (like terracotta pots or clay pots) then you need to soak it well before filling it with potting soil. If the garden pots are pre-soaked then the walls of the garden pot will not absorb moisture from the potting soil. If the garden pots are not soaked then the potting soil will shrink away from the sides of the pot and result in a gap where the water will run off when the pot plant is watered and will thus leave the middle of the potting soil in the pot dry.
You need to ensure that there are enough drainage holes in the garden pots. Enough drainage holes translate to a minimum of four holes of 1 cm each in a pot that has a 45 cm diameter. These drainage holes should be covered with crock, which are essentially shards of terracotta pots. No crock no problem. You can also use a piece of gauze or shade cloth. Take care not to block the drainage holes. It is best to place a layer of river sand over the crock in the pot to prevent the drainage holes from becoming blocked as well as to act as a filter that will prevent the organic compost material and potting soil from washing out. The layer of river sand should not be thicker than 3cm as you would not want to take up too much of the potting soil space. (Tip: When you have small garden pots it is best to use gauze.)
It is also a good idea to add moisture-retaining granules to the potting soil. You should water the pot plant well before planting it out into your garden pots. Now fill the garden pots with potting soil to accommodate the root ball of the plant. Remove the plant from its bag or pot, fit it carefully into the pot, fill up with potting soil around the root ball and firm down. Leave a space of about 5 cm below the rim to accommodate easy watering.
Water the pot plants regularly as they cannot send roots down into the soil as they would were they planted in beds. Add a layer of organic compost to act as mulch or mulch with bark chips or nutshells to keep the soil damp as well as make an attractive soil cover. (Tip: Plant colorful annuals to serve as living mulch.)
When planting outdoor plants that were cultivated in a greenhouse or shaded area in the garden pots take care to keep them in the shade after being planted into the garden pots before placing it is direct sunlight. Rather move them in stages into the direct sunlight so as to prevent the foliage getting burnt by the sun.
It is necessary to repot a pot plant on an annual basis. You will notice that roots start to protrude from the drainage holes, growth becomes stunted, or the plant does not flower as it should. These symptoms will all indicate a need to repot your container garden. Repotting can be done in ten (10) easy steps:
- Before starting, make sure that you have enough potting soil, a new garden pot, and the correct tools for the job. Ensure that your new garden pot is about one third larger than the old one.
- Tie up the foliage that might be damaged during the repotting process.
- Turn the garden pot onto its side. Tap the rim of the pot with the palm of your hand while rotating the pot. The vibration is an attempt to loosen the root ball. In the event of the pot plant being root bound or stuck, pry the root loose with a thin stake. Alternatively you could make use of water to blast out the pot plant by using a sharp jet of water from a hose through the drainage hole and then around the edges. As a last resort, you might need to break the garden pot.
- Carefully ease the pot plant and root ball out of its garden pot. While still on its side, remove the crock that was used around the drainage hole.
- Pry loose old potting soil and loosen any root bound roots, except if the pot plants have sensitive roots such as the bougainvillea, conifers and roses.
- Place some crock around the holes of the new garden pots and cover them with a layer of river sand and then cover with fresh potting soil.
- Pick up the plant by the root and not by the main stem. Place it into the new garden pot. Check that the old potting soil level will be at the same level in the new pot.
- Fill in with fresh potting soil, firm the potting soil around the roots as you go. Ensure that there are no air pockets so that minimal subsidence will occur later.
- Don’t fill your garden pots to the brim leave enough space so that water can dam up and soak in. Firm the surface of the potting soil so that the pot plant is firmly supported.
- Water the pot plants in your garden pots well with enough water to run out of the drainage holes, leave to settle for approximately fifteen minutes, and water well again.
When transplanting pot plants from one garden pot to another, you need the next garden pot to be just one size larger and not too big. This will ensure that the pot plant and the garden pot still look in proportion and not over-potted.
In the event of stunted growth in the pot plant, as a result of restricted root space, you might want to use the same garden pot. The pot plant will need repotting after a few years to keep it in good condition, and this can be done during winter. You will need to remove the pot plants from the garden pots and wash the garden pots well both inside and outside. Shave off a few centimeters of the root ball and return it to the garden pot with fresh potting soil. You may also use this opportunity to trim and shape the plant.
Watering, feeding and pruning in container gardening
Container gardening requires regular watering. Watering is vital. In the hot summer months you will be compelled to give your container garden daily attention, especially if the garden pots that you use are of the porous type. The general rule is to water pot plants well and allow excess water to flow out of the drainage holes. After that it will only be necessary to water again once the top 6 to 8 cm of the potting soil in the garden pots is beginning to dry out. In general outdoor pot plants should be watered once or twice a week, except for summer. Indoor pot plants should be watered once a week to once every ten (10) days, taking into consideration factors such as room temperature and air conditioning. There is no hard-and-fast rule for when to water; it depends entirely on where the garden pots are located and the climatic conditions that it is exposed to. Never leave a plant standing in a saucer of water for more than an hour as this leads to over-watering, water-logging and damage to roots.
It is a given that certain nutrients will be leached from the potting soil whenever excess water runs through the drainage holes. You will need to add fertilizer regularly every fortnight throughout the active growing season in summer. Do not add fertilizer to pot plants when the potting soil in the garden pots is dry. It will result in root burn. Always apply fertilizer after a good watering. Nowadays it is so much easier to care for in container gardening in that plant food sticks can be used. The plant food sticks usually contain slow release nitrogen which makes using these sticks very convenient.
Pot plants also require regular trimming, shaping, and pruning. The standard shrubs and trees fall into this category. You should pinch back new shoots regularly to promote bushier growth. You can also remove about a third of the top from the plants that require winter pruning.
Top tips for successful container gardening
- Buy sterilized soil for use in the garden pots. This will ensure the potting soil that is free from disease and weed seeds.
- When planting be on the lookout for weeds such as onion weed (Nothoscordium gracile) and yellow nutsedge (Cyperus esculentus) once these weeds established themselves it is hard to get rid of them.
- Grouping garden pots is better and more effective visually than scattering them. Smaller garden pots can also be brought inside.
- Do watering late in the afternoon when evaporation is less.
- Add fertilizer and plant food sticks on a regular basis.
- Repot plants regularly as a means of soil amendment.
- Choose the correct size garden pots for your pot plants – if you are using large garden pots then you should first choose the position for your pots, place it in position and then fill it with potting soil. Carting soil-filled garden pots about is not easy and you can hurt yourself in the process.
- Make use of mulch, organic or inorganic, to discourage weed growth and encourage surface roots.
- Most plants are light sensitive and before moving plants from a shady to a sunny spot you should prepare the plant for the move by hardening it gradually. This will prevent sun burn.