As I write this, it is mid-January, and I just finished weeding in my garden. The sun is so pleasantly warm, and I am picking peas, chard, kale, and lettuce from my winter garden. The days are getting a bit longer, bulbs are showing their faces, and my mind is moving towards my spring garden.
As is always the case in Marin, with its many microclimates, planting in spring is a moving target. Generally, the frost season is over by mid-March for those of us who see frost, but coastal and other areas with more marine influence may not see any frost all year. Spring planting calendars are based on the first date following the last predicted frost date.
In Marin, soil temperatures generally average between 40 and 60 degrees in March. At this time, you can start to sow some seeds directly into the outdoor soil. Soil thermometers are available if you aren’t sure. If you haven’t already done so, it is also a good time to start some of your warm weather choices indoors. The Master Gardeners are working on their pollinator plant and tomato grows.
Cool season veggies that you can plant by seed now are beets, carrots, radishes, peas, and leafy greens such as chard, spinach, and lettuce. If you have some space, consider sequential plantings of peas and lettuce until around May to keep your crop going. Where it’s hot here in the summer, these cool-weather crops tend to bolt. Try different varieties of all these cool season crops. There are so many to choose from. Seed potatoes can also go in the ground once they have begun to sprout. You may have planted broccoli, cauliflower, or Brussels sprouts in your winter garden, but if not, try them now. Again, try something new to you.
March is a good time to lift and divide summer and fall-blooming perennials. Daylilies, chrysanthemums, hostas daisies, and coreopsis are easy to divide and will do much better and look much better when they get room to stretch.
Annuals such as nasturtiums and sweet peas can also go in the ground now. You can try to sow some of the summer annuals outdoors, but it may be a bit early for good germination. There are so many more choices if you start your flowers from seed, so consider starting them indoors under lights till it’s a bit warmer outdoors.
Remember the gardening basics for any season as you consider your March garden.
- Make sure you are using fresh seeds. The packages contain expiration dates (or when you are less likely to see good germination success). Seeds that are not properly stored can also be ineffective.
- Prepare your soil. Hopefully, you started in the winter, but it is never too late to pamper your soil. Rich, balanced organic material gives your seeds and seedlings a happy place to thrive. Since spring here in Marin can bring showers, do not work or walk on soggy soil. It compacts the soil particles, squeezing out oxygen and giving the new roots a more challenging place to spread.
- Think through where you are planting. The right plant in the right place is a Master Gardener mantra. The spring sun is beginning to reach a higher arc and changing the light around your garden.
The Marin Master Gardener website can fill you in on the details of the principles I’ve put here. Or call us or email the help desk. Subscribe to the Leaflet for quarterly seasonal advice to grow by.
By Dot Zanotti Ingels, March 1, 2025