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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Mar 31

In the Greenhouse: A Tale of Three Soils

Posted on March 31, 2017 at 3:34 PM by Ann Vallee

by Charlene Burgi

This week's agenda included spending several days in the greenhouse planting perennials in one-gallon containers and placing vegetable seeds into coir pots for an easy transition into the outdoors once the garden soil reaches the right temperature for them to thrive. I also double dug the soil in the greenhouse’s built-in beds and planted seeds directly into the beds for year-round edibles. 

Planting mediums
 Planting mediums
The work consisted of three different types of planting, with each requiring a different technique to ensure the various plants and seeds will prosper. As a result, I found myself working with three different planting mixes. Why three different mixes? After all, soil is soil—right? And is it even soil?

In studying each bag of planting mix, I noted one was darker than the others and contained a lot of heavy organic material including bark remnants. Instinctively I knew this would be the best choice for the perennials that prefer a moister environment. The organic material in this mix will retain moisture for longer periods of time. Most of the perennials I needed to put up are shade-lovers such as ferns and bleeding heart (Dicentra), which will appreciate sinking their roots into this rich mix. 

The second bag contained soil with a more sandy consistency and notably refined organic material. The finer sandy particles of this mix will allow water to move through more quickly. Plants such as succulents, Kniphofia, lavender and Agastache are happier in this type of growing medium as they don't like their feet wet. In fact, I would venture to say that most water-conserving plants do not like to be in soggy soil for any length of time. 

The third bag contained a very light mix of perlite. This is an excellent medium to start seeds as the water moves rapidly through the planting cells, preventing the seeds from rotting in heavy soils. New roots grow easily through this medium, and it provides the light and warmth needed for optimal growing conditions for tiny seedlings. Since perlite drains quickly, it is imperative to keep moisture at hand during this early phase of a plant's growth. And did I mention this mix contained no soil?

Bagged soil: It offers solutions to many planting needs, but be sure to read the label before purchasing to ensure you have the right medium for the right plant.


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