Window Sill Gardening

Window Sill Gardening with African Violets and Gesneriads

African violets and members of the gesneriad family such as the gloxinias, Streptocarpus, and lipstick plants will thrive in conditions that are easy to achieve in most homes once some basic environmental conditions are addressed.   Window sill gardening is not free of challenges, but these are not insurmountable and overcoming them makes the rewards that much nicer.  One of these challenges is dealing with light levels that vary depending on the window orientation and time of year.  Indoor gardeners may have to use a compromised window for plant growth that is not the ideal situation.  Supplemental (artificial) light may be the answer to this problem.  Another challenge is the temperature of the growing area.  The best light might be up against the window which is also the coldest location.  Gesneriads are sensitive to cold and hot temperatures that are beyond a comfortable range.  Indoor environments during the winter also have the challenge of low humidity levels.  This is one of the easier challenges to overcome by using a humidifier. 

Normal home temperatures that are comfortable for people are well suited for gesneriads.  During the daytime, temperatures should be between 20 and 25 degrees (67-75 F.) Celsius for most of these plants.  A five degree drop in night time temperatures is ideal and may even encourage blooming.  It is critical for gesneriads to avoid excessively hot or cold drafts from an open door, fireplace or furnace vent.  Generally, a comfortable environment for humans will be suitable for these plants. 

 Most gesneriads are from tropical parts of the world, although there are some semi-hardy members such as Ramonda which is from the high altitude mountainous regions of Asia, Europe, and South America.  The most common member of the gesneriad group is the African violet (Saintpaulia ionantha) which is from the Tanzania and Kenya region of east Africa.  African violets in their native habitat grow on the banks of streams or as epiphytes on trees.  About 2,000 cultivars in white, pink, red, blue, violet, cream and yellow colours have been developed as a popular indoor plant.  Many advancements have been made to the original plant found in Tanzania which was a light to dark blue colour.  Other gesneriad family members are the trailing lipstick plants (Aeschynanthus species) which are epiphytes from the sub-tropical forests of the Himalayas, south China, Malaysia, Indonesia, and New Guinea.  From the tropical rain forest of the “New World” in Brazil come the goldfish plant (Nematanthus) and gloxinias (Sinningia species).  Gloxinias are gesneriads that have a single fleshy tuber. When the dry or cold season arrives in their native environment, the foliage dies down but the tuber remains alive.  When weather returns that is more suitable for growth, the plant starts to grow from the energy reserves in the tuber.  An interesting plant that is a tuberous gesneriad is the cupid’s bower or hot water plant (Achimenes).  This easy-to-grow plant is dormant during the winter and springs to life in the spring.

 African violets, the most famous gesneriad family member, were discovered by Baron Walter Von Saint-Paul in 1892 in Tanzania.  Upon its arrival to Europe it received the botanical name of Saintpaulia ionantha.  The genus name obviously commemorating its discoverer, but the species name is from the Greek language meaning “having flowers like the violet’s”.  This gave rise to the common name of African violet which give the impression that this plant is a true violet.  African violets are not a violet; they just looked like one to people back in the early 1900’s.   These plants soon became favoured because of its small size, free-flowering abilities, and ease of growth.  This has continued for over a century as more and more people are attracted to the wide variety of cultivars now available.  African violets have now become the most popular flowering indoor plant.  They now come in white, blue, purple, red, and yellow colours with bicolor, ruffled, or double petals.  The foliage might be green, reddish or variegated and leaf margins are sometimes finely serrated, ruffled, or lobed.  To add another dimension, there are now very popular African violets that are miniature and even trailing types. 

 One of the keys to getting African violets to bloom is to have adequate light levels.  Many gesneriads will not produce flower buds if the light intensity is not high enough.  The amount of light that is present on a cloudy winter day is the minimum amount needed to produce blooms.  To ensure that plants receive as much of this natural light as possible, set them in a south or southwest facing window during the winter months.  They must be moved to an east or north window during the summer months because the stronger rays may cause damage to the leaves.  In the summer, an alternative to a south window is to set the plants back away from the window or behind sheer drapes.  Another note is that the sun’s rays striking African violets from one side will cause the plant to grow lop-sided.   Turn your plants one quarter of a revolution each week to preserve their symmetry.  An easier solution might be to grow African violets (and other gesneriads) under fluorescent lights.  This is the only solution for gardeners who do not have south facing windows during the winter.  Fluorescent lights will provide an even distribution of light and can be used with a timer to ensure that African violets get more than 12 hours of light so that they will continuously bloom. 

 African violets are native to an environment that is warm and humid with temperatures that do not drop below 18 degrees Celsius (65 F.).  Keeping temperatures around 25 (77 F.) during the day and five degrees lower at night will be sufficient for good growth and flowering.  Dropping the temperature five degrees at night will produce larger flowers with more petals and brighter colours.  The ideal humidity, between 40 and 60 percent, is often a challenge to achieve during the winter.  Low humidity levels will cause leaves to curl and become crisp at the edges.  Bloom quality may decline too.  To help solve this problem, place a shallow tray of water near the plants so that it will evaporate and humidify the air, group plants together, or use a humidifier nearby.

 Watering African violets the right way is a technique that will pay off with big flower rewards.  Use room temperature water that has sat for several hours to let the gaseous water treatment chemicals leave.  Water early in the day so that the plant is not excessively wet during the night.  Water as soon as the soil surface feels dry to the touch.  Add enough water to the top of the pot so that it runs out the bottom and into the saucer below.  Let this sit for about one hour and then drain the water from the saucer.  African violet roots are susceptible to damage from overwatering, drought, and cold water.  Some gardeners insist that watering from the bottom is the correct way to water gesneriads.  This can be done if careful attention is paid to the amount of time plants sit in the water.  Root damage can happen fast.  Watering from the top also flushes out fertilizer salts so that they do not build up in the soil. 

 Fertilizers for flowering indoor houseplants should have a higher phosphorous number.  This is the middle number of the ratio.  Fertilizing with a weak solution every time the plant is watered will provide a more constant feeding for the plant.  Use one-quarter strength (or less) depending on the frequency of watering.  A dormant plant that is not blooming or coming into bloom should not have any fertilizer. 

African violets (and most gesneriads) should be grown in a sterilized, light soil mixture that is peat-moss based.  Air space in the soil is very important for healthy roots.  The best pots for growing gesneriads are the ordinary plastic ones.  These will hold moisture well and are light to pick up.  Clay pots may accumulate salts around the rim that could damage African violet stems.  African violets can stay in the same (3-4 inch) pot for years because these plants do not have an extensive root system. In time the plant, with its overhanging leaves, may seem very out of scale to the pot.  When the plant is 3 times wider than the pot, it is time to move it up to the next larger sized pot.  Repotting should take place in the spring.  Let the plant dry out slightly so that the leaf petioles are somewhat flexible before repotting or else they may snap off.

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