University of Maryland Extension

Maintenance of Houseplants

 Rex begoinias pansy orchid Schefflera houseplant

Light, water, temperature, humidity, ventilation, fertilization, and soil are the chief factors affecting a plant’s growth, whether it is indoors or outdoors. Excesses or deficiencies of any one of these factors can prevent a plant from growing properly indoors. Because the environment is more rigid and controlled, problems can occur earlier and can be more severe.

Light

Light is probably the most essential factor for houseplant growth. The energy derived from photosynthesis, and plant growth and health, all depend on the amount of intercepted light. Houseplants can be classified according to their light needs — high, medium, or low light requirements. The three important aspects of indoor light are intensity, duration, and quality.  Each one has a different impact on the plant.

Watering and Soluble Salts

A common question home gardeners ask is, “How often should I water my plants?”  The plant itself will tell you. When it’s too dry, a plant wilts and turns gray-green; when too wet, it drops leaves or turns yellow. Avoid both extremes. Plants should not be watered on a schedule, but watered when they need it. Factors that influence plant watering include differences in potting media, humidity, and temperature. 

Temperature and Humidity

  1. Temperature

Excessively low or high temperatures may stop growth or cause a spindly appearance, foliage damage, leaf drop, or plant failure. However, most houseplants tolerate normal temperature fluctuations. 

  • In general, foliage houseplants grow best between 70° and 80°F during the day and from 60° to 68°F at night;
  • Most flowering houseplants prefer the same daytime range but grow best at nighttime temperatures of 55° to 60°F;
  • A good rule of thumb is to keep the night temperature 10 to 15°F lower than the day temperature to induce physiological recovery from moisture loss, intensify flower color, and prolong flower life; and
  • Indoor plants, especially flowering varieties, are sensitive to drafts or heat from registers.  Protect them from sudden, brief changes in temperature.  Do not locate your houseplants near heat or air conditioning sources.

    2. Humidity

Most indoor environments lack sufficient humidity for healthy houseplants, particularly in the winter. With the exception of the cacti and succulents, all houseplants benefit from treatments to raise the humidity in their vicinity.

Mist plants frequently. Early in the day is best to allow the foliage to dry and reduce the risk of disease. An alternative is to place pots on a tray filled with pebbles and water to increase humidity in the area around the plants. If you group plants together in a room, they will collectively raise the humidity in their area. An automatic humidifier can provide extra humidity for plants and people in the home.

Fertilizer

The goal of fertilizing houseplants is to add just enough nutrients so that the new growth compensates for leaf loss. The purpose should not be to encourage quick growth of a large plant. Large amounts of fertilizer are therefore unnecessary for most indoor plants.

Fertilizers come in many different forms; liquid, granular or tablet. Slow-release pellets which release over a period of 3-4 months are also available.  They can be incorporated into the potting soil when planting or applied to the surface. Commercially available fertilizers labeled for houseplants are fine, mix according to label directions. Many will give you a choice of concentrations depending on whether you prefer to fertilize once a month or at each watering. 

Remember the following points when trying to balance your houseplants’ nutrients: 

  • Micronutrients are deficient in many houseplants, so replace them once a year. Fertilizing with a commercial fertilizer labeled for houseplants which contain micronutrients or adding a small amount of well-composted, screened leaf mold or other compost will fill this need. 
  • Because magnesium leaches from the soil at each watering, replace it with a solution of one teaspoon Epsom salts per gallon of water. Water two times each year or use the solution as a leaf spray;
  • During the winter months, houseplants don’t need fertilizer because reduced light and temperature result in reduced growth. Fertilizing at this time could harm some plants. Fertilize from March through September;
  • Monthly applications of a diluted liquid fertilizer in the summer months will keep most plants healthy; earthworm castings are an excellent houseplant fertilizer; and
  • Excessive fertilizer results in the buildup of salts and excessive, leggy growth.

Potting/Repotting

Although plants can grow in a surprisingly small soil volume if they receive adequate nutrients and water, healthy houseplants will grow better and benefit from being repotted occasionally. It’s time to repot if you see the roots of a foliage plant growing out of the drain hole. Late winter and spring is the best time to repot plants. 

Prepare your supplies before repotting. Choose a pot that has drainage holes in the bottom. The diameter of the new pot should be only two inches larger than the current pot. Moving a plant to a larger pot with an excessively large volume of soil can lead to water logging of the roots because the plant can’t use the available water.

If you’re recycling a used pot, scrub soluble salts off with water and a brush. Then wash disease-causing organisms from the pot in a solution of one part liquid bleach to nine parts water.  Allow the pot to dry thoroughly before placing the plant into it.  Purchase a sterile potting medium and moisten the necessary amount ahead of time.  The day before you plan to repot a plant, be sure to water it well to reduce possible shock to the root system.

 

 

 

 

 

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