Substrate Type and Its Effect on Seedling Germination and Growth

Over the past year, I’ve been experimenting with different substrate types for my Lithops. I whole heartedly agree that adult Lithops belong in a nutrient poor, well-draining, course mix. The risk of rot is very high when one uses commercial potting soils; at least, that has been the case in my experience. Seedlings, however, have proven to be entirely different.

I have noticed that seedlings grown in the same nutrient poor, well-draining, course mix favored by mature Lithops are slow growing and remain small through-out their first year. I’ve had excellent germination and survival rates in these pots, but the seedlings have failed to really thrive. In contrast, seedlings grown in 50% commercial cactus soil and 50% course mix grow quickly, complete their first leaf renewal, and attain a decent size (one which would allow re-potting) within 9 months. Germination rates are consistent with the soil-less pots, but survival rate is a little lower as there will inevitably be some dampening off. I also consistently have an overgrowth of algae in these pots, but it doesn’t seem to bother the seedlings much at all and is soon forgotten once the robust plantlets are transplanted in their soil-less adult mix (usually shortly after their first leaf renewal).

These are my observations. I’m not passing judgement on which method is actually correct. I have yet to see these soil-less seedlings become fully mature and it is completely possible I will prefer their compact bodies to the bloated bodies of those originating from the richer pots. I do like the idea of keeping the seedlings in their original substrate over a longer term then has been possible with soil mixes. But one definitely must be more diligent with watering soil-less pots as they do dry out much more quickly. I suspect my lazy watering habits have contributed to the small size of these plants, at least a little.

 

It’s Here! I got Pumice!!!

Okay, I’m a little excited.  My pumice arrived today!

This was quite the adventure.  As you may know, Pumice is impossible to source in Canada and many of the foreign suppliers no longer ship here.  Many growers, myself included, have been forced to find alternative substrates and I’ll be honest, I’m happy using chicken grit and turface!  But, if you hang out on a Lithops forum long enough, you’ll soon start to desire this unicorn of substrates they call Pumice too.  Is it really that amazing?  Is it worth the time and expense to ship it in?  Will my Lithops sigh with relief while I fill their pots with these new stones?  We shall see!!!

And because I’m a girl of my word, I’ll tell you where I got it from!  I ordered directly from a bonsai supply store in Texas – http://www.dallasbonsai.com.  And in the interest of full disclosure, it was expensive to get it here, but at this point, it was about the principal of getting it, not really about the stones anymore – LOL!

It’s also important to note that these stones are small (they also come in medium and large) so I bought a sieve to sift out the fines.  I’ll be able to use the fines for sowing seeds though so I don’t expect much waste.  I couldn’t imagine discarding any of it after what I went through to get it here!

 

Water Bombs

It is important to note that Lithops, unlike other plants, have not evolved the ability to stop taking up water once they’ve had their fill. Lithops evolved in very hot and very dry conditions and it was important for them to take in all available water whenever the opportunity presented itself. In their natural habitat, it was rare for there to ever be an overabundance of water so the Lithops genus never needed to self-regulate their water intake. When you think of this, it makes sense that if you over water a Lithops, it will drink until it bursts – literally!  So we need to discard the old wives tale that ALL plants will only take up as much water as they need.  That is simply not the case for our charmingly unique Lithops.

 

Tough Love

I’m practicing the concept of ‘Tough Love’ with my yearling Lithops.  It’s hard…on me.  If you noticed my post on the violent leaf renewal a few of the yearlings are going through right now, I stated that I was going to withhold water under the new plants emerge and the old leaves are almost fully absorbed.  This is consistent with the treatment for adult Lithops, the difference being the yearlings are all out of whack with their timing and really shouldn’t be renewing at this time of year.  Anyway, the pots are dry and I can see some of the plants are becoming quite pouty.  When I look closely, however, I can see most of them are starting to split open and I can see new plants forming inside.  Let’s hope those that are not split, but still very wrinkly, are planning a renewal at this time too and I’m not just depriving them of water for nothing!

 

Sandy vs Organic Soil Mix

As promised, I’ve mixed together a new soil mix using sand in the place of cactus and volcanic soil.  I did this to maintain the consistency of my mix, but reduce how rich it is in terms of nutrients.  Ratios are not quite 1:1:1:1 as in the organic mix, but that’s because I feel substrates used for Lithops, regards of type, should not clump together and form a ball when squeezed.  Using equal parts sand in my mix caused it to pack together too tightly, so I reduced the amount of sand.  Sadly, I was in a rush and didn’t count my scoops 😦  Roughly, I think this is the recipe:

• 1.5 parts river rock
• 1.5 parts clay gravel
• 1.5 parts perlite
• 1 part course sand

Doesn’t it look a lot like the substrate Lithops grow in naturally?  I’m excited to see how these two mixes stack up against the gritty (bonsai) mix!