How to protect your plants from the cold

The signs of spring are here: gaily blooming plum trees, the waxy petals of magnolia flowers, fields of brilliant yellow mustard adorning the vineyards, narcissus and daffodils everywhere, bees visiting manzanitas, and the courting behavior of birds. The signals and signs of spring are everywhere, and with lengthening daylight hours, we are drawn outside into the garden to begin planting our spring vegetable garden.

Early March is generally a perfect time to begin the process of preparing the soil, planting our starts, and seeding vegetables like greens, early broccoli, cabbage, Japanese greens, peas, beets, carrots, radish and onions. Right now visually we are cued to begin this process, but the prolonged cold temperatures have been daunting - both to our inclination to work in the garden and to plant growth. This precursor to springtime has been a challenge for many of us who grow a winter and early spring vegetable garden.

Cold air temperatures mean cold soil temperatures. Cold soil is not conducive for plants to grow or seeds to germinate, and the ensuing slow growth makes them vulnerable to being eaten by slugs, snails, or birds. Seeds may rot, or fail to germinate. Seedlings may freeze in the coldest areas.

Our existing winter vegetable plants are practically freeze-dried in many of our gardens and are not looking good. Many of our winter and spring vegetables have some degree of frost hardiness. Cold temperatures vary depending on where you live. Some areas are practically frost free, while others regularly endure winter temperatures with lows from the mid-twenties and even high teens.

Some factors that influence winter low temperatures are proximity to the coast and the moderating effects of the ocean.

Being on a slope, even a slight one, will also affect temperatures. Cold air is heavier and flows downhill. It tends to accumulate in the lowest valleys or low pockets. With the first fall frosts you can see the cold air’s actual dimension in vineyards by the vines frosting in a recognizable pattern of cold air pooling in a specific area.

Vines just a small degree higher in elevation may not initially be frosted at all. Even the coldest locations in our area may have a “banana belt” at higher altitudes.

The temperature at 1,000 feet may be as much as 10 degrees warmer in winter than the valley floor, influenced by warm air, which is lighter and so rises.

Even very cold hardy plants like kale, cabbage, broccoli, radicchio and chard can be damaged by days of freezing temperatures, particularly if it is also dry. They may just not grow. The lengthening days in early spring signal to many of these plants it is time to flower. Now is the time to replace them with young starts, or by seeding them.

What can we do to preserve what we have in our gardens until our new starts begin to grow, and how can we protect and encourage our new seedlings?

Watering

It seems odd to advocate watering in winter, but if the rains don’t come regularly, it’s a necessity. Poke your finger in the soil, or dig into the soil with a weeding tool or old screwdriver to determine if your soil is dry. If so, the plants will benefit from watering once or twice a week to keep soil evenly moist.

Row covers

Cover beds with row covers. The spun polyester row covers give a great deal of frost and cold protection to plants. Row covers are breathable and let rain through. They don’t need to be taken off and on. They basically create a mini-greenhouse for plants and help warm the soil by trapping heat.

Even the lightest, (and cheapest) row covers do a great deal to ameliorate frost and create conditions for plants to easily grow in. The heavier grade of row cover does prevent some light transmission, but lasts longer. Row covers are not just great for your winter garden, but also serve to protect tender and heat-loving summer vegetables like tomatoes and zucchinis in spring. Many people use floating row covers over citrus trees in winter to protect them from freezing.

Floating row covers come in different sizes and thicknesses. Long lengths are perfect for covering a 3-foot-wide bed of any length, and large squares or rectangles cover larger areas.

It is simple to cut to size. Ideally, row covers should be held above the plants with wire or PVC pipe hoops. It can be weighed down on the sides by bricks or stones, or anchored with wire stakes.

Row covers are also designed to be laid over a bed and lightly “float” over the plants. Just make sure to give the fabric some slack so as they grow; plants won’t be constricted. If temperatures become warm, make sure to water new plants regularly as temperatures can be warm under it.

Cool-season vegetables that have a low degree of frost hardiness really benefit from these row covers, and the use of them can allow them to persist far into the winter, or to be planted early in the spring. Lettuce and peas are both marginally frost-hardy, and are also relished by birds. Both do very well under row covers.

Deterring slugs, snails

Slugs and snails may have accumulated in weeds, or in vegetables that have overwintered, and are capable of doing much damage to young seedlings. Sprinkle nontoxic Sluggo around plants to kill slugs.

Don’t dig wet soil

Though it has been unusually dry, recent rains have moistened soil in some areas, so it may be too wet to dig. In this case just top dress or mulch the soil with compost where you want to plant. Compost can be used as a top dressing, dug in, or used both ways. In vegetable gardens, make sure to use very nutritious and high-fertility composts like Sonoma Compost Co. Hi-Test Compost, and Pt. Reyes Compost Co. Double Doody - my personal favorites - but there are other good ones as well.

Kate Frey’s column appears every other week in Sonoma Home. Contact Kate at: katebfrey@gmail.com, freygardens.com, Twitter @katebfrey, Instagram @americangardenschool