The Adventure Begins:
The key to growing cactus from seeds is that unlike other plants, cactus seeds need direct sunlight (or grow lights) to germinate, so you must place the seeds on top of the soil, not under the soil.
My best advice is as follows:
1 - Use Cactus Soil. This comes with the Odd Pods package and can be purchased separately if you have just purchases seeds.
2 - Sift the soil into a number of small ~ 2 inch planters, eliminating any clumps with your hand.
3 - Thoroughly moisten the soil - but make sure that there is no standing water.
4 - Evenly sprinkle 6 to 10 seeds on top of the Cactus Soil in each 2ď planter (don't cover with soil)
5 - Place the planters where they will receive maximum sunlight. You can also supplement this with a grow light or even florescent lights.
6 - Your seeds will sprout at different times but you should see seedlings within 5 to 7 days.
7- Once the seedlings appear, use a spray bottle to mist the seedlings to keep them from drying out.
8 - Remoisten the soil every 3 to 4 days for the first few weeks to prevent it from drying out.
9 - Once they get bigger water them every 3-4 weeks as necessary.
In the beginning you need to prevent the soil from completely drying out without over watering. It's a delicate balance for the first few weeks. After that most plants require watering once every 2-4 weeks (bigger plants once every 3 to 4 weeks). If mold starts to appear, reduce the moisture and water the plants with a mixture of one capful of hydrogen peroxide to 7 ounces of water. This will kill the mold but not the cactus.
The next bit of advice is to start out with about 1/3 of the packet the first time. This way, you can learn from your mistakes (if any) and try again once youíve gotten the feel of things without ordering more seeds. I have one client who managed to grow ~ 70 cactus plants from one packet of seeds but she is an expert. Most people will be lucky to end up with 20 to 30 plants. Personally, I used the entire packet the first time and managed to get 6 plants, which promptly died because I didnít water them enough. My second attempt was much better until my wife accidentally knocked the planter off the kitchen counter (I think it was an accident, but I do have over 100 cacti in the house = )
By now, Iíve probably made it sound over complicated and youíve probably given up all hope. But with ~150 seeds to play with, you donít really need to be an expert, especially if you split the packet into thirds and try to grow them at three separate times.
The most important advice is to just have fun with this! Watching the seedlings sprout and grow is fun and even if you only end up with half a dozen plants itíll be worth what you paid for them! For even more fun, try using some imaginative planters. For example, I found a Terra Cotta Chili / Salsa Bowl, which really wasnít meant for plants as they have no drainage holes. But if youíre careful to not over water the plants, they work just fine. And if you DO over-water the plants, you can soak up the excess water by carefully pressing down on the soil with a wadded-up paper towel.
Garage sales and flea markets are also great places for finding unusual planters and if kids are involved, finding the right planter can turn into a treasure hunt. With a little imagination, you can turn this into a fun adventure that the kids will remember for a lifetime. Best of luck and happy planting Ö