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Microbes for Houseplants

Plants don’t share the proverbial groundhog’s pessimism about sun at this time of year. They just respond positively to the increasing length of sunlight hours. Even houseplants will emerge from winter dormancy and start to grow again soon.

How support that growth? Although photosynthesis provides plants’ main food, they also need nutrients from the soil. But in a pot you can’t sustain the complex ecology of organisms that make a healthy soil in the earth. (There just isn’t room for earthworms, for example.) Without the soil organisms, many nutrients are locked in forms unavailable to plants.

People commonly assume what plants need will be supplied if fertilizer is in a liquid form. Of course chemical liquids further damage the soil ecology, and contribute imbalanced nutrition. Plants may look lush, but they’ll be unhealthy, weak, and attractive to pests.

Natural liquid fertilizers, like fish emulsion and seaweed emulsion, certainly are healthier for plants. I bought a case of what I thought was seaweed emulsion, because Ward objected to the fish smell. Unfortunately, it was a combination of the two.

Many places sell dry fertilizer packaged into what look like large teabags, which you put in boiling water and steep for half an hour, then pour the cooled liquid on your plants. I’m skeptical that water — even boiling — can extract everything plants need from the dry ingredients. In fact, I’m skeptical that just because anything is in solution means it can accomplish what the soil foodweb does.

In the garden, compost is a good answer. Compost tea (made by soaking finished compost in water for 12 to 24 hours), also contains lots of microbes — but it’s extremely perishable.

Many people rely on organic potting soil, made from a compost base, to provide microorganisms. But in order to keep the microbes alive, I need to make sure the soil doesn’t dry out, either in the bag or in the pot. I keep failing at both.

Earthworms eat soil; as it passes through them nutrients are converted to forms most absorbable by plants. Worm digestion also contributes a wealth of enzymes and microorganisms. You can buy worm castings from Agway in Milford (ask for WiggleWorm Soil Builder). But I’m going to try some fresh from a worm grower, the Down-to-Earth Worm Farm of Vermont (see <>, or call 802-533-9836). This rich stuff comes in a smaller bag than soil: perhaps I can manage to keep it moist.

© Copyright 2005 Catherine Holmes Clark

Published in the six Nashoba Publications papers on Friday, 28 January 2005

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