Growing Streps by Jim Graf

The Streptocarpus, also known as the Cape Primrose, is a relative of the African violet and a member of the Gesneriad family. It was first discovered in South Africa in 1826. Its name means “twisted fruit” (streptos -“twisted” and carpus -“fruit”), because the seed pod of this genus is twisted, similar to a unicorn’s horn.  It was cultivated throughout the later half of the 1800’s and in 1880, an orange flowered variety was developed. This variety, when crossed and back-crossed with its pale blue counterpart, has helped to  produce the wide range of colors that we see today.

Streptocarpus are divided into 4 groups.  All of the groups have fibrous roots but differ in their growth and flowering habits. One group grows with erect stems and leaves that grow in opposite pairs. The other group is stemless, and this group is divided into 3 subgroups based on flower types. Some members of this group are single leafed varieties, while others grow in rosette forms.

There are a wide variety of Streptocarpus available to today’s growers.  Some exotic flower and leaf types grow a single leaf that can be 24” long and 12” wide with flowers that are 1 ½” long.  Others have flower stems that are a foot long. Some streps have only one leaf and generally do not bloom until their second season.

The habitats of the Streptocarpus in their natural environment are varied. Some grow in the open but are partially shaded by overhanging rocks. Others prefer forest shade by stream beds.

Cultivation of streps is also greatly varied. Some plants are monocarpic, meaning that the plant dies after flowering and setting seeds, while others will bloom as biennials.  The common varieties that we grow today are mostly perennials and will grow and bloom as long as their growing requirements are met.

The growth requirements for Streptocarpus are similar to African Violets and they can be grown in the same areas of the home.

Light: The plants enjoy bright, indirect light to partial shade in the summer and full sun in a southern exposure in the winter. Under artificial light, 12-14 hours a day is recommended for good plant growth and flowering.

Temperature: Streps like temperatures slightly cooler than violets. Day temperatures of 65-75 degrees and night temps of 55-65 degrees are best for most varieties, and placing the plants lower on your plant shelves or in a cooler part of your growing area will promote best growth.

Water: Keep plants evenly moist but not wet!  Wet soil may cause root rot and letting the soil dry out may affect flowering.

Humidity: 60-70% is recommended. Make sure that good air circulation is present to avoid fungal infections.

Soil: Use African violet mix or one part potting mix, two parts peat and one part course perlite or sand. The mix must be well drained and porous for good root growth.

Fertilizer: Apply a well balanced fertilizer at 1/8th strength at every watering will help promote lush, green growth.  A high phosphate fertilizer at ½ strength every 2 weeks is another option.  Be careful not to fertilize when the soil is dry, because leaf burning may occur.

Dormancy: Plants generally have a 2-3 month rest period after blooming. When growing indoors under controlled conditions, many Streptocarpus may bloom continuously given the proper conditions and if leaf and plant growth continues. Allowing the soil to dry out for extended periods or high temperatures in the growing area may trigger dormancy.

Propagation: Propagating Streptocarpus can be done in a variety of ways. These are:

Seeds: Seeds are sown in a soil mix consisting of 2 part loam, 2 parts coarse sand, and 1 ½ parts peat moss. Since Streptocarpus seeds are one of the smallest seeds known (1.75 million seeds per ounce), the seeding bed is first saturated with water. The Srep seeds are then brushed from the palm of the hand onto the seed bed. Immerse the seed bed in ½ inch of water and keep the water this level until removing the small seedlings, which appear after approximately 6-8 weeks. Re-pot the new plantlets into a mix similar to the seeding mix or plant mix listed above.

Leaves: Propagation of plants by leaf cuttings is the most common way of multiplying plants. Cut the leaf in 1-2 inch strips and cut down the mid-rib of the leaf. After allowing this leaf piece to callus for approximately 15 minutes, place the leaf cutting mid-rib down in a mixture of 1 part perlite and 1 part vermiculite, with charcoal added to help prevent rotting. Tiny plantlets will appear along the leaf rib, at the junction of the veins. The leaf can also be cut like a violet leaf, making a petiole out of the midrib and inserting this into the cutting mixture. Plantlets will form at the base of the petiole and can be removed after they grow to 1”. Leaves  will also produce plantlets if placed in  water, but the leaf may rot if submerged in water.

Division: Plants can be divided to make multiple numbers of plants. Using a sharp knife, cut the plant apart between growing crowns, getting as many roots as possible for each plant. Plant these in smaller containers, being careful not to over-pot. Streptocarpus like to be slightly root-bound and over-potting promotes root rot.

 Insects: Pests that are common to the African Violets are also common to Streptocarpus. Soil mealy bugs and thrips are common pests, and white fly and red spider mites may also affect the plants.  It is important to check each plant that is added to the collection and isolate these plants from other plants for a minimum of  3 months. This will help to minimize the chance that something unwanted will be introduced into your collection. Keeping your plants well groomed will also help to control pests.

Grooming: Leaves may be trimmed if dry edges appear.  Make sure that a sharp utensil is used, such as a sharp scissors or razor blade.  This will help minimize bruised leaf edges. Removing dead flowers and dying leaves from the plant will help keep your plants looking in top shape. While grooming, make sure to check for any abnormalities of growth, which could indicate pests or disease.

Streptocarpus plants may be purchased through many reputable dealers, most of whom specialize in African violets. I have had good luck with Rob’s Violet’s, which feature the Bristol series of streps in many beautiful colors and flower types. Most catalogues have color pictures and descriptions of Streps and other gesneriads and there are many new introductions each year. Some of my favorites are: St. ‘Lemon Drop’, a pure white flower with a lemon yellow throat, St. ‘Bristol’s July Fourth’, a red flower with splashes of cream and white on the petals, St. ‘Suzie’, a large, bright red flower with yellow throat, and St. ‘Ruffles ‘n’ Pink’, a large deep pink, ruffled flower with a creamy yellow throat.  Again, remember to isolate the plants when your order arrives!

There are also many web addresses on the internet that give growing advice and give users a chance to ask questions and get growing information. Most of these deal with Gesneriads as a whole so some searching may be needed to get the desired information.

Streptocarpus are growing in popularity as fun and welcome additions to the collections of many African violet growers. I have had great luck growing these violet cousins right next to my African Violets. The various growing styles, colors, and flower types of Streptocarpus, as well as relative ease of growing and extended blooming period are great reasons to try these beautiful and unique plants.

Text by James Graf

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