Streptocarpus Myths

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Robert Pavlis

The first hybrid streptocarpus was released in 1946 and since then hundreds of new cultivars have been developed and yet few people are familiar with them. I predict that will change. Streps are easy to grow house plants that can flower all year long. What other house plant gives you that much star power in a small package. They are even better than orchids because they flower more and are easier to take care of.

However, even this lesser known houseplant has started to generate some gardening myths. Let’s have a look at some here.

Streptocarpus Myths
Streptocarpus Myths, source: streptocarpus.ca

Streptocarpus Roots Grow Towards Water

I found this claim in an article written by one of the top streptocarpus breeders in the world and published in Gleanings, the Gesneriad Society Publication, “These roots display strong hydrotropism (ability to grow toward water), which enables them to find water from a distance. You can easily observe it when a strep grown in 100% humidity sends a root up in the air.”

This is a common myth that is claimed for all kinds of plants, not just streps. Roots DO NOT find water at a distance.

Soil Science for Gardeners book by Robert Pavlis

Most roots do display hydrotropism. What this means is that as roots grow they bend towards the side that has a higher soil moisture. This may sound like it is the same as growing towards water, but its not. If you place a root in dry soil near some water, the root will not grow towards the water. Similarly, if you place the root in soil that is equally wet all around the root, it will not grow towards a wetter location. The root can only sense water that is touching the root.

Once you understand this you will also realize that claims about roots growing towards cracked water pipes is also a myth except in the special case were there is a water gradient between the pipe and the root.

What about those roots that grow up in the air?

If you keep a plant a bit wetter or in high humidity the plant will make vertical roots that leave the soil and grow straight up. Some native streptocarpus are lithophytes, plants that grow on rocks. In such conditions they get moisture from the air and they can do the same in our pots. Orchids are also able to pull moisture out of the air.

Streptocarpus Yellow Pink Cap, source Streptocarpus.ca
Streptocarpus Yellow Pink Cap, source Streptocarpus.ca

Streptocarpus Grow Just Like African Violets

Since steps are relatively new plants for most indoor gardeners, growers like to help them out with simple advice – I have even done it myself. We tell them streps grow just like African violets because most gardeners are familiar with them.

This advise is better than nothing, but it is not really true. In the wild African violets grow in low light conditions among jungle trees. Streptocarpus grow in much more open spaces and prefer filtered light. In the house they grow better with higher light than African violets from either light fixtures or direct morning light from an East facing window.

African violets like to grow in soil with a high level of organic matter which tends to stay wetter. Streptocarpus like less organic matter and a soil that drains better. African violet soil is commonly recommended for streptocarpus, but this soil does not drain enough for them. If you use it, mix in 30 – 50% perlite to increase drainage.

Cause of Leaf Dieback

Leaves have a basal meristem where growth takes place. As leaves grow the new tissue at the base pushes the older leaf tip away from the center of the plant. This means the tip of every leaf is the oldest tissue in that leaf. It is quite common for the tip to turn brown and dry which is referred to as leaf dieback. It is more common in autumn and winter especially for plants grown on windowsills but it can occur on any plant that is stressed by drought, low temperature or root damage. Simply cut off the end of the leaf and the plant will be fine. This can be a straight cut or some people cut it to a point to look more natural.

Mutated Leaf Growth

Some growers get concerned about so-called mutated leaves that have a lighter tip as shown here.

Streptocarpus goetzei, in the wild, showing a clear abscission layer
Streptocarpus goetzei, in the wild, showing a clear abscission layer, image copyright Patrick Blanc

This phenomena is unusual in most plants but quite normal for some streptocarpus. Many deciduous plants grow leaves during the summer and then drop them in fall to get ready for a winter rest. Instead of dropping the whole leaf, streptocarpus only drops the tip of the leaf preserving the meristem at the base. By fall their leaf is too big to support all winter and so it drops some of it to preserve nutrients and sugars. An abscission layer is formed in an arbitrary location somewhere in the middle of the leaf. Nutrients are moved from the tip back to the lower part of the leaf and this loss results in a light green or yellow tip. Once the separation layer is fully formed, the tip of the leaf will fall off.

Water Sitting On A Leaf Will Cause Rot

I see this comment all the time – you should not wet the leaves or they’ll rot. I found this claim odd – do these plants grow in places that don’t have rain?

So I did a little experiment. I took a strep with a long, fairly flat leaf and put water on it daily for a couple of weeks. No rot!

I water from above and nearly always get water on leaves and even in the crown of the plant. No rot!

I also watered one too often by putting the water right on the soil – it rotted the roots. This one was not part of the experiment.

Streptocarpus can’t be too wet around the roots or they rot. Getting leaves wet is not a problem.

I think this claim may stem from the fact that in African violets, and probably streptocarpus, cold water can cause damage to leaves. It is not really the cold in the water but the differential between the leaf temperature and the water temperature. So a room temperature water put on a hot leaf can cause damage.

Growing Streptocarpus

I am not going to go into detail here, but the link below will take you to a series of videos that provide the basic information your need. The most important thing to remember is that these plants grow in relatively dry locations in the wild. They can take some drying out, but they can not be too wet. Use small pots, plant them high so the crown is dry, Use well drained media and DO NOT OVER WATER. If you get the watering right, you will have no trouble growing them.

YouTube video

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

12 thoughts on “Streptocarpus Myths”

  1. Regarding roots growing towards cracked water pipes:
    Never seen it but I have seen three cases of cracked sewer pipes being invaded by roots.
    No doubt the easily available nutrients were what brought this about.

    Reply
    • Roots do invade cracked pipes – no one questions that. The question is how did they get there. Did they sense water at a distance and grow towards it, or did they just grow in all directions and thereby they found the cracked pipe. Without a water gradient – the latter is what happened.

      Reply
  2. Thanks so much for the info. I love these plants but don’t know where I can purchase them (St Catharines area) My Mom once had one, a friend started a plant from a clipping. I have never seen them in a store. Thanks

    Reply
  3. I love streps–have several–with my violets–I grow both violets and streps in about three houirs of morning sun–before 11:00. The streps do great–but so do the violets.

    Reply
  4. I got one from a local african violet grower. Beautiful and always blooming. We had bad issues with powdery mildew on it. If its prone to that, it may be the reason they say don’t get the leaves wet?

    Reply

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