Thinking ahead - Marin Independent Journal

UC MARIN MASTER GARDENERS

Thinking ahead

Preparing raised vegetable beds for a bountiful growing season

The results of amending the soil in January can be seen later in the summer season when the vegetables planted in March and April thrive in the raised bed during the summer months. JILL FUGARO — MARIN MASTER GARDENERS

After moving irrigation tubing out of the way, the raised vegetable bed is amended with a mix of peat moss or coconut coir, compost and vermiculite. PHOTO BY LINDA STILES

Kale, lettuce and nasturtiums thrive in their amended soil in the summer months. JILL FUGARO — MARIN MASTER GARDENERS

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By Jill Fugaro

IJ correspondent

January is a great time for Marin County gardeners to prepare raised vegetable beds for the upcoming growing season. Amending the soil in winter months ensures that the beds will provide vegetables with the rich nutrients they need when planting time for summer crops arrives in late March to early April.

First steps

Before amending, it’s important to assess the condition of the soil in the beds. Over the previous season, nutrients are depleted from the soil if you’ve been growing heavy feeders like tomatoes, peppers or squash. In our Mediterranean climate, hot summers dry out the soil, causing it to lose structure. Compacted soil may need physical loosening and amendments to improve texture.

Testing your soil pH and nutrient levels will help you determine which amendments are needed. Simple soil kits are available in most garden centers. Generally, most crops grow best when the pH is slightly acidic to neutral, between 5.5 and 7.5 — 7.0 is neutral.

Backbone of healthy soil

The key to healthy vegetable beds is rich, organic matter. Incorporating high-quality compost and well-rotted (aged) manure into your raised beds improves the soil’s structure, moisture retention and nutrient content. Organic matter feeds the soil’s beneficial microorganisms, which help break down nutrients and make them available to plants and attract earthworms.

If your soil test indicates the need for amendments to get the right pH and balance of nutrients, obtain those specific amendments.

If you make your own compost, great, use it.

If you don’t make compost at home, that’s OK. You can mix different brands of store-bought compost to make sure to get a balance of nutrients in your veggie beds.

Improving soil texture

Adding sand, perlite or vermiculite to heavy soils can improve aeration and drainage. Sandy soils, on the other hand, can benefit from the addition of organic matter to increase moisture retention. Ensuring that water can drain freely from the beds in the rainy season is crucial to preventing root rot and other moisture-related issues.

My recommended formula for the amendment mix is one-third peat moss or coconut coir, one-third compost/manure and one-third vermiculite by mass (not by weight). I mix these three equal mounds in a wheelbarrow. If you don’t have a wheelbarrow, use a tarp on the ground, where you can mix them thoroughly with a spade or shovel before lifting the tarp and pouring the mix onto the beds and spreading evenly.

Figure on adding 2 to 3 inches of amendments to existing raised beds. Add 6 to 10 inches if the bed has been out of commission for a while.

Here’s the calculation for covering one bed 9 feet long and 4 feet wide with a layer of material 3 inches deep: 9 feet by 4 feet = 36 square feet by .25 feet deep = 9 cubic feet total. If you’re mixing three different types of compost, that equals 1 cubic foot of each compost brand (3 cubic feet total) added to 3 cubic feet of peat moss and 3 cubic feet of vermiculite or perlite. A typical wheelbarrow holds about 3 ½ cubic feet of amendments.

Preparing for spring

Amending your raised beds in January sets the stage for a productive growing season. Whether you’re adding organic matter and nutrients or improving the texture of your soil, the work you do now will pay off when your vegetables begin to flourish in the spring.

For more detailed soil preparation information, go to marinmg.ucanr.edu/EDIBLES/COVERCROPSETC">marinmg.ucanr.edu/EDIBLES/COVERCROPSETC.

Sponsored by UC Cooperative Extension, the University of California Marin Master Gardeners provides science- and research-based information for Marin home gardeners. Email questions to helpdesk@marinmg.org. Attach photos for inquiries about plant pests or diseases. Please call 415-473-4910 to see when a master gardener will be at the office or drop off samples 24/7 in the sample box outside the office. To attend a gardening workshop or subscribe to Leaflet, a free quarterly e-newsletter, go to marinmg.ucanr.edu.