Streptocarpus Dimetris

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PostPosted: Tue Feb 11, 2014 12:13 pm 
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Joined: Mon Oct 08, 2012 12:09 pm
Posts: 311
Streps’s thriller: who kill my plants?

We decided to write this article because many people ask us about conditions in which we grow our streps. Sadly, many customers complained that they very often their streps die or do not do well. We always were puzzled by that, because we can’t kill our streps.

We think that the most important aspect of growing streps is the soil.

To understand the soil requirement for Streptocarpus we need to understand where native Streptocarpus species live. Many S. species are lithophytes (plants, developing on the rock) and epiphytes (a plant that grows on another plant, such as a tree), and derive their moisture and nutrients from the air, rain, and dust. That is why S. root systems are very well adapted to get nutrients from very poor, airy substrate. It also explains S. resistance to dry conditions. Most native Streptocarpuses cannot tolerate rich, heavy soil.

Now it is easy to understand the following soil requirements for Streptocarpus and plants in general.

• Soil must physically support growing plant.

• Soil should be light, airy. Media must provide adequate gas exchange between roots and
atmosphere. It is important not only for the roots breathing (respiration), which provides energy to the roots, but also for normal development of beneficial microorganisms.

• Soil should retain some water.

• The substrate must contain the optimal amount of macro- and micro- elements in accessible

forms. Exception are carbon and oxygen, which plants get from the air.

• Soil should be structurally stable.

• Soil must have buffer capacities. Buffer capacity it the ability to maintain certain acidity/alkalinity.

During a last few decades, mostly soilless media is used. First formulated at Cornel University, it has become very popular, because of many advantage over the field soil.
Currently many soilless mixes exist in the market. Main components of these mixes are: peat moss, perlite, vermiculite.

Many commercial mixes contain these components in different proportion and add many other ingredients.

Let’s talk about peat moss first. It is partially decomposed organic material that is primarily the remains of different types of mosses. Peat mosses are usually acidic. The pH is the measure of the acidity, which can range from 3 to 7 in different peat mosses. Also peat has good water retention, up to 60% of its own weight. Peat has some ion exchange ability too.

Vermiculite has a high capacity for holding water. Vermiculite can soak up 3 to 4 times its volume in water. Because of its very high ion exchange capacity it also attracts plant nutrients such as potassium, magnesium, calcium and phosphorus. The pH of vermiculite is 7.0 to 7.5.

Perlite is inert, light-weight volcanic rock mineral. Perlite has a pH of 7.0-7.5, is chemically inert, and has no cation exchange capacity. Perlite provides excellent drainage and increases air pocket in the growing media. Perlite also holds some water, but not as much as Vermiculite.

Peat moss, perlite and vermiculite from different sources have different characteristics.

Commercial soil vendors also often add macro- and micro-elements.

Peat moss based soilless potting mix has low pH. To neutralize high acidity of peat moss, neutralizing agents like dolomite, lime etc. should be added. It is very important to add the right quantity of neutralizing agent. Dolomitic lime is frequently used because it also supplies the calcium and magnesium needed by plants.

Perlite and Vermiculite also buffer growth media. Perlite is rated low in its capacity for pH buffering, and vermiculite is rated high.

Because peat based mixes are difficult to re-wet once dry, a wetting agent may be added.

Finally, commercial soil may have beneficial microorganisms like fungus Micorrizae. Mycorrhizae fungi increase the surface (absorbing) area of roots up to 1,000 times. This fungus also help to dissolve hard-to-capture nutrients, such as organic nitrogen, iron and others.

Let’s now return to soil requirement for Streptocaprus. As we saw, there are many important ingredients that need to be in a potting media. One might wonder, how Streptocaprus exists in nature. Nature is an open system, however, to recreate natural condition in a small pot is a complex task. That is why we strongly recommend not to mix your own soil. Since Streptocarpus have some unique soil requirement, such as extra airy, high drainage, poor soil, it may be impossible to find such soil. However, if we need to make soil, the fewer components we mix the less possibility to make a mistake.

We successfully use PRO-MIX® BX BIOFUNGICIDE™ + MYCORRHIZAE This amazing mix has few different bacteria inoculates that prevent root rot and few other fungal diseases. My plant sometimes stay in water and don't get root rot. Mycorrhizae is a beneficial fungus that greatly increases the plant's capacity to absorb more water and nutrients. Unique PRO-MIX Biofungicide does not harm beneficial fungus Mycorrhizae.
We add 3-4 part of this mix to one part of perlite. We use medium grade or coarser perlite. For leaf cuttings propagation the previous mix will work. However, the lighter mix - one part Pro-Mix BX and one part perlite - is even better.

For propagation, Sphagnum (not peat moss) can be used in place of perlite, or even as a sole ingredient. Dry Sphagnim can be cut with scissors, crushed with hands.

It is important to note that as more and more native Streptocarpus species are incorporated in hybridization, new varieties may have different soil requirements. We will not discuss it here, but will show just one example. Salt-sensitive hybrids such as DS-Aphrodisiac, DS-Lacy Cloudlet and others need different soil.

Please note that we do not grow our plants on mats, we do not use wick or special pots (like Oyama pot). These approaches require even more porous, airy soil. We are not expert in growing Streps these ways and will not give any recommendation. We water our plants from the top like other house plants.

Who kill my streps???

Now we return to the problems many growers have with their streps.
Since we did tried to kill our plants with no “success”, we can draw some conclusion from it.
Who is the enemy? Here are our thoughts.

The plant is a complex system. Its health depends on many parameters. The more non-optimal parameters the greater chance that plant will not be well or die. It is like humans. If you have flu, but on top of that many other ailments, your recovery will be longer.

Light. Streptocarpus grow well on windowsills, but condition on windowsill are not stable during the year. We grow our plants under artificial light. Although we’ve heard that Streptocarpus die for people under artificial light, we can say that light is not a killer. We checked light tubes with different characteristics and so far did not find any that kills the plants. For people that grow under artificial light we can say that light is not a killer.

Temperature. Streptocarpus can withstand a wide range of temperatures (from 40 to 90). 80-90 should not be for a long time. Best interval is 50 F (especially at night) to 75. Most people have their streps within that range. Temperature is “acquitted.”

Pot size and shape. We found that our plant do not need azalea-type pots, shallow pots. Moreover, evaporation from the surface of these pots are quite high, which leads to more frequent watering and salt accumulation. We purposely planted our streps in tall drinking cups and did not find any differences. As long as pots are much smaller than you plants, we can’t “accuse” the pots.

Water. Water can differs tremendously in pH, salt concentration, toxins etc.
Water can be a culprit. We don’t know to what extent. Streps do not like hard water. Water softeners are not the solution since they just replace one ion with another. We recommend using Reverse Osmosis (RO) water. By using RO water you exclude this parameter (water) as a possible culprit.

You can use distilled water. It is Okay if you dissolved fertilizer in distill water. However, when you pot your leaf fragments or babies or re-pot adult plants it is recommended not to use fertilizer at all if you use RO water. Since distilled water does not have any ions (RO water have very small amount) it can impose osmotic shock to the plant. That is why if your water is distilled water we recommend to use weak fertilizer, about 1/10 of standard strength (see below).

We use a RO water system that fits under the sink (Lowes, around $150) It is very good for pets and people too.

Watering with RO water. Since we have hundreds of plants we can’t make special accommodation for each plant. Sometimes they stay dry and “drop their ears”, sometime they are watered when their soil is are wet, sometimes we water only from one side, sometimes we don’t add enough water to wet the entire pot, sometimes pots bottom are touching the water level on saucer. Please don’t think that it is a good practice to neglect plants. We are only trying to show that if you use RO water, watering is unlikely the enemy.

Please water your streps when soil is dry to touch, the pot is light in weight. Experiment and wait one time when leaves start to loose turgor and next time try to water just before that. It is always better to under water than over water.

Fertilizer. We know from experimenting with different fertilizers that it is one of the crucial factors necessary for Streps growth and flowering. But it is the one that it easy to control, by buying right one. We will not elaborate on this matter in this article, since we already have some information about it on our forum. We only use Peat-Lite Special 20-10-20 that we order online. We add 1/8 tbsp/Gallon. Since it is difficult to get such a small amount, we prepare concentrated (stock) solution first. Dissolve 20 ml of dry fertilizer in 1 quart (liter) of water. Keep it in a closed plastic or glass container. Add 25 ml of stock solution to 1 gallon of water. Since our plant are under the light we use that solution each time we water our plants.

We are also in process of analyzing many different fertilizers. Hopefully, we will find one that that is readily available.

Finally, the potting soil. We are convinced that the main enemy is the wrong growing media. Since good potting soil contains many components that quite often vary from batch to batch and we don’t have the right equipment at home to check final mix, we strongly recommend buying the commercial soil. We use Pro-Mix BX and add 1/4-1/5 amount of perlite or Sphagnum (not sphagnum peat). It may be a little more expensive than to mix your own, but in the long run, it is worth it. We are sure that with time we will find more good commercial mixes.

Last thought – when you re-pot, the distance between roots and the pot’s wall should be around 0.5”, but not significantly more. Soon we will post video about different re-potting situation.

Very last thought. Even great Streps’ potting mix can’t last forever. Under artificial light and with constant supply of fertilizer our plants grow very fast. Re-potting every 2-4 months is necessary if you want to have healthy, flowering plants. However, you can’t kill you plant if you don’t re-pot for a year.

Very, very last thought. We just was trying to prove that the temperature, light, RO water, pots, can’t kill you plants. However, if you take these parameters in theirs extremes and combine them together, problems can occur. Example: plant grow under dim artificial light that far away from your plant, at 90 F, in large pot and watered every day.


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