OBSERVATIONS
ON SEED GROWING
Nowhere is there more conflicting advice in the cactus world than in seed germination and growing. Every book seems to say something different.
"Cover the seeds"
"Don't cover the seeds"
"Grow in a pot covered in a plastic bed in the dark for 6 months"
"Seedlings need light and air"
"Water from the top"
"Water from the bottom"
"Repot after six months"
"Don't repot until the seedlings are at least 12 months old"
(These are all samples of advice we read in books before we started. Somewhat bewildered, we experimented ourselves)
We are no experts in seed growing (this is our 3rd year of trying), but we have observed growth patterns which may be beneficial to you - although we realise that some of these tips may only apply to the seedlings we're growing.
Some background:
All seeds were germinated in B & Q cactus compost
All seeds were planted in the March - June period
We purchased a heated propagator nearly 3 years ago.
Year 1
In the first year I noted how quickly germination took place. After a few weeks they were taken out to start some more (greedy, on reflection)
Result - most of them dried out and died, or produced weak specimens. All of the ones marked deceased on the Seed Watch page came from year 1. Only about 10% made it.
Year 2
I placed the pots on a J-cloth in the propagator and kept it wet (it makes far more sense to water seedlings from the bottom to me - if the water is below, root growth will occur - if you water from the top, there is less need for the plant to grow a strong root system). I kept the germinated seeds in the propagator for 6 months. I took about half of each type out and overwintered them outside the propagator. Those overwintered in the propagator kept growing (even though they were in the original compost), those outside (in new compost) less so, but we lost none. (I kept both sets well watered).
Year 3
One never knows when it says "slow growers" as to how slow with regards to seedlings, so we changed another variable. Some of the pots were overcrowded so after only 2 months, I thinned them down - repotting half into new soil and then putting them back in the propagator. The results were startling - see below. We can only surmise that the first few months takes a lot of nutrients out of the soil, and repotting them gives them a boost.
Rebutia tropaelipitica - all the seedlings were germinated at the same time in the pot on the left. After 2 months, those on the right were put into fresh soil. Other than that, the growing conditions were identical - heated propagator, same light, same water. The photo is after 4 months - so you can appreciate the change in growth rate.
Was this a fluke? The two pots below were similarly treated - they are of Echinopsis atacamensis.
I've since repotted all the seedlings in the left hand pots and they are catching up with those in the right pots.