This paper will be about how the cactus killer can be someone whose windows look like those at the florist's, written from personal experience and some knowledge. The illusion of a green thumb is actually easy to create: all you need is some knowledge and a few hints, which will be provided as you read along.
The bottom line is that plants which will thrive at certain locations will have requirements and needs that are catered to at that location: a plant that needs near 100% air-humidity will not survive without considerable care above a radiator, a location of very dry and warm air. A plant might survive, but it will not look good, if the amount of light is not right: far too little is lethal, too much or too little will damage the plant through burns or weak (and ugly) growth.
Temperature is in most cases not crucial, room-temperature will do for most common plants. Never expose thte plant to a heatsource such as a fire in a fireplace, which can do extensive damage. Core-temperatures above 45 C are lethal for any plant. A cold draught is bad for a great number of plants.
In general the air in modern homes is very dry, especially in winter. Therefore the species to choose are those that tolerate dry air--e.g. the Asparagus-family and succulent plants--if you want them to look nice and green without the painstaking task of frequent spraying with water. You can choose the approach of having a group of plants, which will create a more humid micro-climate around them. Using a humidifier is a good idea in winter, both for you and the plants. Plants that need a very humid atmosphere can be grown in bowls or bottles (clear glass only!): I have a baby's tears (Soleirolia soleirolii) that thrives this way.
How much light is present will determnine to an extent the choice between variegated (=multi-coloured) or dark green plants. The rule of thumb with many exceptions is that the variegated forms need a lot more light than the green varieties of the same species. If you have plenty of sunlight at a wwindow facing South, then the scale tips to some succulents or the sun-loving variegatas, if you like them: "too much light" shouldn't be in their vocabulary--they simply decrease the amount of green in the colouring and become more spectacular, and detecting too little light is easy: if the colours fade, move the plant to a better-lighted place. Florescent species, that is plants that blossom and flower, usually tend to be a lot more sensitive and demanding of both care and environment and available light. There are exceptions: species such as Spathiphyllum, Chlorophytum or Hibiscus rosa-sinensis are florescent, but very easy to take care of.
Artificial light--that is, lamps-- can be used to provide extra light. However, they need to be especially designed for that purpose (the composition of the spectrum of light is essential) and you need to have a lot of them to be of any use.
So far I have discussed what you need to know and take into account before you obtain the plants, as these variables you can't do that much about if you want to remain lazy. Optimum pairing of environment and requirements means minimum care. To have success with minimum vare demands doing your homework: read books, ask people who know about plants, determine the amount of light, how much space you have (some plants become HUGE fast, like my Asparagus falcatus), whether there is a draught or a radiator (dry air) nearby...
The one thing that can go wrong after such carefully done research and coming up with suitable species is watering the plants. This is where most mistakes are made in the care of the plants, and they can be lethal for the plant or greatly reducing their appearance and health.
Contrary to common belief, cactuses are very difficult to water correctly. Too much water will kill the cactus, and you might not be granted a second chance through recovery. Some plants need an abundance of water, demanding a fine line of near-drowning--one single dry day can cause the plant to wither just as likely as a drowned day can. On the other hand, most succulents like to dry up to a certain degree between waterings. If this demand is not met, the rootsystem faces the danger of rotting, and this is lethal.
Fortunately, there is an abundance of plants in the happy mean that are not overly particular about watering. These can successfully be grown in ordinary pots without constant monitoring or a capability of telepathy with the plant. An occasional dry spell is not a catastrophe, but care should be taken that there never is water on the plate, which would prevent the soil from breathing, thus causing the roots to rot. Another common mistake is that too little water is given too often: it is better to water well and less often in most cases, allowing the soil to dry up a bit before watering. Most people use the weight of the pot or feel with a finger the dampness of the soil to find out the current status of the plant. Most plants want more water when they grow well: the more light, the more water is needed. Warm conditions also demand more water. Most plants grow very little in winter due to lack of light, and therefore they should be watered less in winter.
Plastic or glazed clay pots are better than unglazed clay pots, because unglazed clay "breathes", causing significantly more evaporation. This in turn means that plants in plastic pots need to be watered far less frequently. There are also devices (hydrogauges) which measure the moistness of the soil to help determine when a plant needs watering. A device which is very easy to use, and which is accurate when "tuned in", is Moistix-sticks, which are permanently immersed to a plant-specific degree in the soil and change colour when watering is needed. Elektor-Electronics has featured an electrical device which has electrodes submerged iin the soil. There are also hydrogauges that are "portable", that is only one gauge, which is taken from pot to pot.
For someone as lazy, absentminded and forgetful as me, self-watering pots (itsekasteleva ruukku, altakasteluruukku) are the ideal solution, together with plants that are suitable for them (e.g. Asparagus, Dracaena, Scirpus, Soleirolia). The pots can be expensive, but are usually very durable. A large plant in a pot with a 5-litre basin can be left unattended for several weeks--something that students who frequently visit their parents for weekends and holidays appreciate. Almost all watering worries are dimished with these pots, and forgetting to fill the water-basin, thus causing a short dryer period, can be even advisable. At least in winter...
Fertilising and repotting plants is not the most important thing in the world. Repot the plant in spring, use a new, larger pot if the pot is filled with roots at least partially, those which grow very fast need more frequent repottting to give the roots the room they need for growing. Do not repot a plant in fall or winter--mostly thre is not enough light to sustain much growth. I have used ordinary plant-soil to all my plants with success. Do not fertilise a plant for at least 4-6 weeks after repotting--many plants don't even require fertilizing if repotted annually. Never use stronger solutions than the package recommends--plants obtain their nutrients through osmosis, and if the nutrient concentrations are higher outside the plant, the process will be reversed: all water will be drawn out of the plant, together with the nutrients, killing the plant.
So, are there any sure bets around? Well, most people should be able to handle a spider plant (Chlorophytum). Asparagus falcatus and the Asparagus densiflorus-varieties should be manageable. Quite a few succulents and semi-succulents are agreeable. Quite a few species adapt to their treatment quite well, as long as it stays the same. It all comes down to trial and error and your own experiences, so never invest much in a plant of a species you haven't tried out beforehand.
spectacular:
My mother's Codiaeum variegatum in extreme sunlight and facing south
has become a mixture of strong, bright yellows, oranges and red and almost
no green at all and it shows no signs of suffering-- on the contrary, it
is thriving in the sun. back
watering:
More exotic causes, such as water-quality, which is of significance
for a few species (Camellias, orchids....), are omitted. back