Scoria, Aloe, and Crinum

Joe Shaw
Sat, 02 Sep 2006 11:04:10 PDT
Hi Gang,

I grow a lot of bulbs in black nursery containers, a practice that helps in 
some ways but which also has drawbacks.

Recently, I decided to calculate the volume of some "5-gallon" containers. 
I guess I should have known, but  even the largest-appearing ones are just 
under 4 gallons in volume, and only if you will fill them with soil to the 
very top.  Other so-called 5-gallon containers are about 3 gallons in 
volume, about 650-710 cubic inches.  That puts them in the 11-15 liter 

When I did the math for a typical 1-gallon can it came in at 0.7 gallons 
(about 2.7 liters).

I did some calculations on a 25-gallon container and it seems to be about 25 
gallons in volume.  I have a few Crinum in such containers and they seem 
happy.  Crinum in smaller containers also seem happy, but I think they 
achieve their best growth in 15 gallon containers, or larger.

Still, tough plants that they are, seedlings will mature and come to 
blooming size in 3-4 years if they are potted up in "4-gallon" containers, 
but they need to be potted up by the time they are a year old.  My old 
practice was to hold half a dozen seedlings in a 1-gallon container (or 
sometimes 2-gallons) and forget about them till their 3rd year, and then I'd 
pot them up or out, or trade them.  They definitely grow better with more 
space early on.

The biggest problem with containers here is that the soil will warm up to 
the overnight low temperatures (sometimes 70-75 F, ca. 22 C).  The soil can 
stay warm for weeks in July and August.  This is at least 10-15 degrees F 
warmer than the soil is 15 inches below ground level.  On warm days, if even 
a little sun hits the side of a black container, the soil can warm up to 
80-85 F on that side of the container.  I don't think the roots like all 
that heat.

For me, Crinum grow their best when planted in the ground and heavily 
mulched.  The 6 inches of mulch shades the soil, helps retain water, impedes 
weeds, and probably has other wonderful benefits.  In such situations, with 
6-8 hours of sun per day, the Crinum have a long growing season.

In contrast, some other plants I grow (Aloe species or Opuntia species) get 
planted in lava rock (scoria).  Then, I dribble in some soil that is mostly 
coarse sand and perlite, and perhaps 10-15% humus.  It can take Aloe or 
Opuntia (and other cacti) a year or more to get used to the scoria-with a 
bit of soil, but once established they thrive.  The benefit from using so 
much scoria (and the inherent air pockets) is that my Aloe and cacti survive 
winters here.

Of course the desert plants always want to rot because of they year-round 
rain and humidity.  Therefore, in addition to the scoria-based soil, I treat 
them with myclobutanil (formulated for lawns, the mealy grains) and they 
seem happy enough.  Fertilizer can run right through a scoria-based potting 
medium, but I like they way my plants grow-not too much unnatural "lush" 

Insects are the greatest problem for Crinum and Opuntia (not Aloe yet). 
Scale and mealy bugs adore Opuntia here near Houston, TX, whereas 
grasshoppers dine on amaryllids.



More information about the pbs mailing list