Houseplant Basics: Home

Houseplants can be easy to grow if you understand your plants' needs and your home environment. Here are some the basic requirements for growing plants in your home.

Light

Household light varies in intensity, depending on the season and the exposure. South-facing windows provide the most light: direct sunlight within 2 to 3 feet of the window; bright, indirect sunlight up to 5 feet from the window; and semi-shade up to 8 feet away from the window. East and west-facing windows provide some direct light up to 3 feet and indirect light up to 5 feet away. East windows get sun in the morning, west in the afternoon. North-facing windows provide semi-shade up to 5 feet away.

Light intensity changes with the season. Plants that fare well in a southern exposure during the winter may have to be moved to an east- or north-facing window in summer when the light is more intense. Remember to keep both sides of your windows clean; dirty windows can block up to 50% of the light. Most plants grow toward sunlight, so remember to rotate the pots ¼ turn every few weeks so that the plants will grow evenly.

Even if there are no natural light sources available, many plants will survive with other sources of light. Light can come from indirect sunlight or artificial lights specifically designed for growing plants.

Signs that plants are not getting enough light:

• Leaves are smaller than normal.
• Leaves are pale.
• Plant exhibits leggy growth.
• Lower leaves yellow and fall off.
• Variegated leaves turn green.
• Plant doesn't flower.

Signs that plants are getting too much light:

• Leaves burn and have scorched patches.
• Leaves wilt.
• Leaves look washed out.
• Leaves dry out completely and fall off.

Water

There are plenty of variables that determine how much water a plant needs. Large plants tend to need more water than small plants. A plant that is flowering or actively growing (producing new green shoots) needs more water than it does during a dormant (resting) stage. Plants tend to need more water during the warm summer months than during the cool winter. Plants in sunny locations need more water than plants in shade. Clay pots are porous and so dry out faster, while plastic pots are better at retaining moisture. Some plants prefer dry conditions, while others demand constant moisture. It all depends on the plant you select, how you plant it and where you place it.

Correct ways to water your plants:

You can use a watering can, water in the sink or even take plants into the shower. Taking your plants into the shower has the added benefit of cleaning dust of leaves and washing away common insect problems.

When watering your plants, use tepid water and water generously. It's much better to give generous amounts infrequently than to give small amounts frequently. You want to thoroughly water the plant by covering the entire soil surface and then let the top few inches of soil dry out before watering again.

Some plants such as African violets, cyclamens and begonias don't like water on their leaves. To water your plants from below, immerse the pots in a bucket, bowl or sink of tepid water. The water level should fall just below the rim of the pot or fill the plant's saucer with water. Allow it to stand for 15 minutes.

Watering Do's and Don'ts

• Do water with tepid water. You don't like cold showers, neither do your plants.
• Do stick your finger or a pencil 1 to 2 inches deep into the soil to see whether it's wet or dry.
• Do water infrequently and deeply rather than frequently and shallowly.

• Do Not water your plants on a strict schedule. Check them first.
• Do Not let your plants sit in water. Empty water from saucers 15 to 30 minutes after you have watered.
• Do Not water your plants (especially the leaves) at night; it might make them more susceptible to disease. Water during the day, although not in the heat of midday unless they are wilting.

Over-watering, rather than under-watering, is one of the most common ways of killing houseplants. Over-watering prevents plants from getting oxygen and causes the roots to rot.

Signs of over-watering:

• Leaves are limp and rotten.
• Flowers are moldy.
• Both new and old leaves fall off the plant.

Signs of under-watering:

• Leaves are wilted or dry.
• There is no new growth on plant.
• Flowers fall off.
• Oldest leaves fall off first.

Temperature

Most houseplants do best when grown at 65 to 75°F in the daytime and 55 to 65°F at night. Many houseplants require a temperature drop of 10°from day to night. Some plants need this drop to induce flowering.

Your house is full of microclimates. Locations near windows may be sunny during the winter, but they are also cool (10°colder than the middle of the room). In the summer, a south-facing window can get too hot for plants. Open the window to let air circulate, or invest in a sheer curtain to block the heat and intense rays of the summer sun. Investigate your home's microclimates in order to put your plants in the best spots.

Soil

One of the most important and most overlooked ingredients for houseplant success is soil. Plants get nutrients, water and stability from their potting mix. The structure of the potting mix is important; plants generally need good air circulation and drainage around their roots. Never use soil from your outdoor garden. It's usually too heavy and may contain weeds and pests that could harm your houseplants.

There are many good potting soils on the market. There are soil-based potting mixes (sterilized) and soil-less mixtures (which tend to be peat-based). Soil-based mixes are heavier and suitable for larger plants that need weight in the containers. Soil-less mixtures are lighter.

Many ingredients go into potting soils: peat moss (lightweight with good water retention), sphagnum moss (water retention), fir bark (drainage), charcoal (deodorant), perlite or vermiculite (drainage and aeration), and coarse or sharp sand (drainage). Different plants require different types of potting mixes: cacti need a sandy, well-drained mix; azaleas need acidic mixes; and most orchids need airy, very well-drained, fir bark mixes.

Humidity and Ventilation

In the summer the humidity in your home is probably 30 to 50%. When the central heating comes on, humidity drops 10 to 30%--about the same as a desert! Tropical houseplants will need some help in these adverse conditions. Several ways to help your plant are:

• Group plants together. Plants transpire (release water) and will raise the humidity in their area.
• Create a dry well: place plants on a pebble tray and add water to the tray or allow water runoff to collect. As long as the roots of the plant are not in contact with the water, you have created a humid local environment.
• Invest in an electric humidifier. It's good for the plants and for you too.
• Plants also need good air circulation. You can improve air circulation by opening the windows on warm days, rotating plants that are grouped together so different sides are exposed to the air or investing in a small fan. Remember that plants do not like sudden changes in temperature or cold or warm blasts of air.

Food

Potting soil usually contains enough nutrients to last a plant for two months. After two months, you will need to fertilize. There are 2 main types of plant fertilizers: water-soluble and time-release. Choose the one that fits your schedule. Time-release fertilizers are good for busy, forgetful gardeners, while water-soluble fertilizers appeal to people who love to fuss over their plants.

The three elements that plants need in large quantities are called macronutrients. Nitrogen (N) promotes green foliage and stem growth and is the dominant component of food for foliage plants. Phosphorus (P) encourages flowering and root development and is recommended to dominate feeds for flowering plants. Potassium (K) contributes to overall stem strength and disease resistance and higher potassium fertilizer is recommended for woody stemmed and fruit bearing plants. Fertilizer ingredients are listed in the formula N-P-K. 5-10-5 indicates 5% nitrogen, 10% phosphorus and 5% potassium. Plants also need calcium, magnesium and micronutrients like iron, copper, manganese and molybdenum in small quantities.

Some simple rules for fertilizing:

• Over-fertilizing is worse than under-fertilizing.
• Fertilize at ¼ to ½ the recommended strength. Plants will do fine with smaller doses.
• Once a month, flush your plants with tepid water. This will clear out harmful deposits of fertilizer salts that have accumulated in the pots.
• Don't fertilize your plants immediately after re-potting them; the new potting soil may contain fertilizer and the plants need time to adjust.
• Don't fertilize sick plants. It's better to troubleshoot and find the problem than to junk it up with fertilizers that are heavy in salts and could just make matters worse.
• Don't fertilize plants that are going through a dormant phase.