Following are the main rules for growing plants in pots.
1. Research your plants. Some plants need perpetually damp conditions while others like to dry out between waterings. You may find it handy to keep your potted plants in groups with similar watering needs.
2. Use bigger pots than you think you need. The most dangerous size is 1 gallon which should only be used for tomatoes seedlings and such that receive daily watering. Individual flowers and herbs should be in 3-gallon pots minimum.
3. Fill your pots to within 2 inches of the top before transplanting. You should use the best potting mix available and add at least another handful of perlite to each pot. Potting mixes never quite use the right amount of perlite. For water-loving plants such as herb celery you can add vermiculite instead of perlite.
4. Do not fertilize your transplants for one month. Never add fertilizer to the potting mix before a transplant. Un-dissolved fertilizer will burn the tips of adventitious roots and can kill a plant.
5. Always over-water. For water-loving plants you can use a saucer to form a reservoir at the base of the pot. Regular plants and those that like dry conditions need to be watered thoroughly and allowed to drain quickly. If you water plants lightly on a regular basis the potting mix within the root ball will dry out. When this happens any water you apply to the pot will run out quickly and not affect the dry root ball. Before your plant dies of dehydration you must put the pot into a basin of water and also add water to the top until the base of the pot is settled. Allow the pot to soak overnight, no longer. By morning your root ball should be damp and healthy.
6. Fertilize with Osmocote which is a time-release provider of nutrients. One application lasts for three months. There are other time-release products but why drive an Aztek when you can drive a Rolls Royce for more or less the same price. Surprisingly little Osmocote is required and it should be worked into the potting medium with your fingertips for best results. Miracle-Gro produces a large range of water soluble fertilizers made for specific plant needs. One promotes flowering, one is ideal for peppers and tomatoes, one is made for acid loving plant, another for roses, et cetera. Miracle-Gro can be added on a fortnightly or monthly basis to give your plants a specific boost. Under no circumstances should you use granular fertilizer for potted plants. This needs to be applied monthly in substantial doses and the saline residue will poison the soil – and your plants – over a period of time because of the confined nature of a plant pot.
7. Move your plants to bigger pots when they become root-bound. Roots escaping through drainage holes are an indicator but you can pull the whole plant and soil mass from the pot quite easily to double check. Move from 3-gallon to 5-gallon, 5-gallon to 10 gallon, et cetera. Before moving to a larger pot, consider moving your plant to the open garden. If you grow a shrub such as a key lime or carambola in a pot it is best to start off with the anticipated pot size you figure you will need for the mature and productive plant. Certain plants. Most notably the Norfolk Island pine, keep to the size of whatever pot you put them in. Although Norfolk Island pines can grow to over 100 feet they stay at 6 to 8 feet tall in 5-gallon containers.
8. Always arrange an odd number of plants in one circular container. This is a gardening tradition that actually makes a lot of sense. A central plant surrounded by four or six plants spaced evenly midway between the centre of the pot and the rim allows each plant a clear area to grow in. Arrange three plants in an equilateral triangle.