Hi, gang. It's planting time in California, so I am once again playing around with soil mixes to see if I can find the ideal formula for my potted bulbs. Several years ago I had what I thought was a clever idea. My usual mix (50-50 sand and peat) made for very heavy pots. So I decided to substitute a lighter-weight ingredient for some of the sand. Perlite is cheap, and inorganic, so I decided that would be a good substitute. I potted a lot of bulbs in a mix of 50% peat, 25% perlite, and 25% sand. It was a very bad mistake. I lost a significant number of bulbs to rot, and many more looked unhappy. For a while I thought maybe there was a chemical in the perlite that killed some bulbs, but finally I realized that perlite retained a lot more water than I thought it would. My mix was too wet. Fast forward to today. Before my next soil experiment, I decided to do a little testing. So I took equal quantities of six potting ingredients, weighed each one, soaked it in water for six hours, poured off the excess water, and then weighed the ingredient again. This told me how much water it retained. Here are the results, with 1 = the amount of water retained by sand. Sand 1 Pumice 1.4 Redwood compost* 1.95 Supersoil** 2.2 Peat moss 2.46 Perlite 2.6 Yeah, the perlite retained more water than even peat moss. No wonder I lost some bulbs. It looks like pumice may be the ingredient I want. It's not quite as lightweight as perlite, but it retains a lot less water. Any thoughts? Mike San Jose, CA *Redwood compost (or redwood soil conditioner) is somewhat-composted redwood shavings, a widely-available mulch in California. Redwood decomposes very slowly, so it makes for a long-lasting addition. **A popular potting mix in California, made of 100% organic material.