March is the month when Sonoma County’s garden stops holding its breath. The last frost dates are receding — though not entirely gone — soil temperatures in most inland valleys are creeping past the 50°F threshold that triggers biological activity in roots and soil microbes, and the shift from bare-root season to spring planting is underway in earnest. If February was about dormant-season opportunity (see our guide to bare-root planting in Sonoma County), March is about waking things up.
In This Guide
This transition is not a calendar abstraction. It is written on the landscape itself. By early March, wild mustard is in full golden bloom across the Dry Creek and Alexander Valley floors, its presence in the vineyard rows a reliable ecological signal that soils are warming and the growing season is opening. Wisteria is leafing out on old arbors along Healdsburg Avenue. The plum trees that line many Sonoma County farmsteads are dropping petals and pushing leaves. Narcissus and early tulips are weeks past their peak and giving way to the later-season bulbs — ranunculus, anemone, Dutch iris.
For home gardeners and landscape professionals alike, March demands both action and restraint. The cool-season window is maturing — if you haven’t direct-sown your peas, lettuce, and root vegetables yet, now is your last reliable chance before heat shuts the season down in May and June. At the same time, the warm-season crops that define the summer garden — tomatoes, peppers, basil, squash — are not ready for the ground, no matter how warm a particular week may feel. Understanding this dual nature of March is the foundation of gardening well in Sonoma County.
The guidance here draws on recommendations from the UC Cooperative Extension Sonoma County Master Gardener Program, the Sunset Western Garden Book’s zone-specific planting calendars, and more than four decades of landscape installation experience in the Healdsburg area.
If you’re just getting started with your seasonal planting calendar, our February planting guide for Sonoma County covers the early cool-season window and the bare-root opportunity that runs through mid-February.
Quick Reference: What to Plant in March in Sonoma County
| Plant | Method | Timing | Notes |
|---|---|---|---|
| Peas | Direct sow | Now | Trellis required; plant thickly |
| Lettuce & Salad Greens | Direct sow | Now | Succession sow every 2–3 weeks |
| Beets, Carrots, Radishes | Direct sow | Now | Loose soil essential for root crops |
| Chard & Spinach | Direct sow | Now | Cold tolerant; great cut-and-come-again |
| Broccoli & Cabbage | Transplant | Now | Set out 6-pack starts now |
| Kale & Artichokes | Transplant | Now | Artichokes perennial once established |
| Sweet Peas | Direct sow | Last call | Soak seeds overnight; needs trellis |
| California Poppies & Larkspur | Direct sow | Now | Do not transplant; scatter and water |
| Ranunculus & Anemone | Corms/transplant | Now | Point side down; excellent cut flowers |
| CA Natives & Mediterranean Shrubs | Plant from container | Ideal window | Establishes before summer heat |
| Tomatoes, Peppers, Basil, Squash | — | Wait | Soil too cold; mid-April minimum |
What’s Happening in the Garden This Month
Before reaching for a seed packet or a shovel, spend a few minutes reading the garden itself. March in Sonoma County is a month of rapid, visible change, and those phenological cues — the observable biological events that mark seasonal transitions — are your most reliable planting guides.
By the first week of March, ornamental stone fruits (flowering cherries, plums, and almonds) are finishing their bloom and pushing leaves. That leaf push is meaningful: it indicates that soil temperatures at root depth have crossed the threshold where biological uptake becomes efficient. Tulips and daffodils planted the previous fall are at or near peak bloom in inland gardens. Artichoke plants that were cut back in winter are sending up vigorous new growth from the crown.
In the vineyard corridors of Dry Creek, Alexander Valley, and the Russian River lowlands, wild mustard (Brassica rapa and related species) has been blooming since late February and is now at full height — often waist-high or taller in uncultivated margins. Winemakers use mustard bloom as a rough phenological marker for the approach of bud break in Pinot Noir, which typically follows by three to five weeks. Gardeners can use the same cue: when mustard is peaking in the vineyards, it’s time to get cool-season crops into the ground without delay.
Native vegetation is also waking. Manzanita (Arctostaphylos) is finishing its bloom period in most elevations. Ceanothus is just beginning to open its distinctive blue flower clusters on warmer south-facing slopes. California poppies are germinating wherever bare soil and full sun coincide.
Soil temperatures in most Sonoma County lowland gardens — Healdsburg, Santa Rosa, Windsor, Sebastopol — will be in the range of 48 to 58°F through March, depending on week and microclimate. The UC Cooperative Extension recommends a minimum of 50°F for most cool-season vegetable seeds to germinate reliably. Use an inexpensive soil thermometer to take the guesswork out of timing.
Vegetables to Direct Sow in March
March is the final month in Sonoma County where direct-sowing cool-season crops makes strong agronomic sense. Seeds sown now will germinate quickly in warming soil and reach harvest before the extended heat of May and June shuts down production in lettuce, spinach, and peas. Don’t wait until April — by then, bolting risk climbs sharply, especially in inland zones.
Peas
Sow peas in the first two weeks of March — this is the outer edge of the planting window for inland Sonoma County. Peas need cool soil to germinate and cool air to produce well; they will set pods prolifically when nights stay below 60°F but decline rapidly once summer warmth arrives. Recommended varieties: ‘Oregon Sugar Pod II’ (snap pea, 60 days, excellent disease resistance), ‘Sugar Snap’ (the classic, 70 days), and ‘Maestro’ (shelling pea, 61 days). Sow 1 inch deep, 2 inches apart, and provide a trellis. Inoculate seed with rhizobium inoculant for best nitrogen fixation and yield.
Lettuce and Salad Greens
Lettuce is the quintessential March crop. Direct-sow loose-leaf types in rows or broadcast lightly over a well-prepared bed; thin to 6 to 8 inches for full heads or harvest as cut-and-come-again. Recommended varieties: ‘Black Seeded Simpson,’ ‘Nevada’ (outstanding bolt resistance), ‘Rouge d’Hiver’ (red romaine, excellent cold tolerance), and ‘Forellenschluss’ (Austrian heirloom, excellent flavor). Sow every two weeks through early April to extend the harvest window. Arugula, mache, and mustard greens can be broadcast-sown at the same time.
Beets
Beets are adaptable to the variable conditions of March — germinating in cool soil, tolerant of light frost, productive over a long window. Sow 1/2 inch deep, thin to 3 to 4 inches. Varieties: ‘Detroit Dark Red’ (reliable, classic), ‘Chioggia’ (Italian heirloom, candy-striped, mild and sweet), ‘Golden’ (non-staining, sweet), and ‘Cylindra’ (long, cylindrical root, excellent for storage).
Carrots
Carrots require patience — germination can take two to three weeks in March soil — but the payoff is worth it. Sonoma County’s loamy and clay-loam soils can challenge long varieties; choose accordingly. ‘Nantes’ types are the standard for home gardens. ‘Chantenay’ types are excellent for clay soils. ‘Danvers Half Long’ handles imperfect soil preparation better than most. Sow shallowly (1/4 inch) and keep the seed bed consistently moist through germination.
Chard, Spinach, Radishes, and Root Crops
Swiss chard sown in March will produce continuously through summer and into fall. ‘Bright Lights,’ ‘Fordhook Giant,’ and ‘Ruby Red’ are all well-suited to the region. Spinach bolts quickly as days lengthen, so sow now and harvest fast — ‘Bloomsdale Long Standing’ and ‘Tyee’ are reliable bolt-resistant choices. Fast-maturing radishes (25 to 30 days) can be sown continuously through March as a catch crop between slower-maturing vegetables. Turnips — ‘Hakurei’ (sweet, salad-type, 38 days) and ‘Purple Top White Globe’ — are productive and underused in most Sonoma County gardens.
✓ Pro Tip: Check Soil Temperature Before You Plant
A $15 soil thermometer is one of the most useful tools in your garden. Insert it 2” deep in the planting area. Below 50°F — hold off on all but the hardiest cool-season crops. 50–60°F — cool-season crops are go. Above 60°F — you can start thinking about warm-season transplants.
Vegetables to Plant as Transplants
Some cool-season vegetables are better established from transplants in March, particularly for gardeners who want to maximize the productive window before summer heat. Purchase starts from local nurseries in late February and early March, or start indoors six to eight weeks prior.
Broccoli and Cabbage
Transplant broccoli and cabbage starts in early to mid-March in inland zones and from mid- to late March in coastal and fog-influenced zones. These crops need several weeks of cool weather to size up properly before heat arrives. ‘Di Cicco’ broccoli (proliferates side shoots over a long season), ‘Calabrese’ (classic Italian, strong flavor), and ‘Green Magic’ (hybrid, uniform heads) are all well-suited to Sonoma County. For cabbage, ‘Early Jersey Wakefield’ and ‘Savoy Ace’ handle spring temperature swings well.
Kale and Artichokes
Kale transplanted in March will produce through summer and well into the following winter. ‘Lacinato’ (Tuscan or dinosaur kale) is the regional favorite. ‘Red Russian’ is cold-hardy with mild, sweet flavor. For artichokes — practically a native plant in coastal Sonoma County — March is an excellent month to plant crowns or starts. ‘Green Globe’ is the standard commercial variety; ‘Violetto’ (Italian heirloom, purple-tinged) and ‘Imperial Star’ (produces in the first year from transplant) are both worth growing.
Flowers to Plant in March
March is a productive month for ornamental gardening, with opportunities to both direct-sow and transplant a wide range of flowering annuals and perennials.
Sweet Peas
Sweet peas (Lathyrus odoratus) are in their peak planting window in early March across most of Sonoma County. They require cool conditions to establish and will bloom from May through June before heat shuts them down. Sow directly in the ground or in deep containers, 1 inch deep, 4 inches apart, with a sturdy trellis in place. ‘Mammoth’ series, ‘Old Spice’ (heirloom, intensely fragrant), and ‘Spencer’ types (large, ruffled flowers) all perform well locally. Sweet peas planted after mid-March in inland zones will often fail to produce before heat arrives.
California Poppies, Larkspur, and Direct-Sown Annuals
California poppies (Eschscholzia californica) can be broadcast-sown now wherever bare soil exists in full sun — they naturalize readily in Sonoma County’s Mediterranean climate and reseed prolifically once established. Larkspur (Consolida species) is another excellent direct-sow choice for March; sow in fall in milder gardens, or in early March where fall sowing was missed. Annual phacelia, bachelor’s buttons (Centaurea cyanus), and African daisies (Dimorphotheca species) can all be direct-sown now for late-spring color.
Ranunculus and Anemone
If you didn’t plant ranunculus corms in fall, you can still find started plants at local nurseries in early March — these will produce their tissue-paper blooms from April into June. Anemones are in the same planting category; both prefer well-drained soil and cool temperatures during establishment. In foggy coastal gardens, ranunculus can be planted now with good success; in hotter inland zones, shade cloth during establishment will extend their season.
Snapdragons and Cool-Season Annuals from Transplant
Snapdragons (Antirrhinum majus) transplanted in early March will bloom from April through June, then often rebound in fall after summer heat subsides. They are among the most rewarding cool-season annuals for Sonoma County and deserve wider use than they get. Lobelia, stock (Matthiola incana — extraordinarily fragrant), and nemesia can all be transplanted now from starts available at local nurseries.
Trees, Shrubs, and Perennials
March is one of the best months of the year to install woody plants — both California natives and Mediterranean-climate ornamentals. The reasoning is straightforward: plants installed now have two to three months of cool, wet weather to establish root systems before summer heat arrives. A ceanothus or toyon planted in March will have significantly better first-summer survival than the same plant installed in May or June.
The UC Cooperative Extension consistently recommends fall and late winter as the primary planting windows for woody plants in Mediterranean-climate California, and March falls squarely within that recommendation. The caveat is that March-planted trees and shrubs will still require supplemental irrigation through their first summer — do not assume that spring planting equals drought tolerance in year one.
California Natives for March Planting
- Ceanothus (California Lilac): Plant now while soil is still moist. Many Ceanothus species are intolerant of summer irrigation once established — install them before heat arrives and give them one summer of careful, infrequent deep watering, then let them find their own rhythm. ‘Ray Hartman,’ ‘Dark Star,’ and ‘Julia Phelps’ are all proven performers across Sonoma County elevations.
- Toyon (Heteromeles arbutifolia): The plant that gave Hollywood its name. A tough, bird-supporting shrub or small tree with white June flowers and brilliant red berries through winter. Excellent for fire-safe plantings in the defensible space zone.
- Manzanita (Arctostaphylos): Just finished blooming, which means March-planted manzanitas have finished their most vulnerable phenological moment and will put their energy into root growth through spring. ‘Howard McMinn’ is among the most reliable for garden use; ‘Sentinel’ has an elegant upright form for smaller spaces.
- Salvia (Sage): The Salvia genus includes dozens of species that thrive in Sonoma County’s climate. Salvia ‘Bee’s Bliss’ is a ground-hugging, drought-tolerant groundcover with lavender flower spikes beloved by hummingbirds. Salvia clevelandii ‘Winnifred Gilman’ is a taller, intensely aromatic shrub sage for drier exposures. Both can be planted now.
Ornamental and Edible Trees
Bare-root season for deciduous fruit trees is winding down by late February, but container-grown citrus, figs, pomegranates, and feijoa can be planted through March with good results. Citrus — in particular, navel oranges, Eureka lemons, and mandarins — do well in Sonoma County’s warmer inland valleys (Healdsburg, Cloverdale, Knights Landing Road corridor) but should be planted in a protected south-facing location. Do not plant citrus in frost pockets or coastal gardens where temperatures regularly drop below 28°F.
⚠ Not Yet: Hold These Until Mid-April or Later
Tomatoes, peppers, basil, squash, melons, cucumbers, and eggplant all require soil temperatures above 60°F to thrive. Most of Sonoma County doesn’t reach that threshold until mid-April at the earliest — and coastal areas often later. Planting warm-season crops into cold soil doesn’t just slow them down; it stunts root development, invites disease, and means a plant set out in warm soil in April will often overtake one planted six weeks earlier into cold ground.
What Not to Plant Yet
This is where March gardening requires discipline. The warm days that come in late February and early March — the days when it hits 72°F in Healdsburg and smells like summer — are seductive, and every year they tempt gardeners into planting warm-season crops too early. Resist.
Tomatoes, peppers, eggplant, basil, squash, cucumbers, beans, corn, and melons all require soil temperatures above 60°F for reliable germination and establishment. Most of Sonoma County does not reach that threshold until mid-April at the earliest, and in coastal zones and fog-influenced areas (Sebastopol, Bodega Bay corridor, Petaluma lowlands), not until May. Plants set out in cold soil will sulk, stall, and often be outperformed by plants installed three weeks later into properly warm ground.
More concretely: a tomato transplant set into 52°F soil in mid-March will sit essentially dormant for four to six weeks, susceptible to root rot and late blight, while a transplant set into 62°F soil in mid-April will establish in seven to ten days and grow vigorously. The later planting often produces its first ripe tomato before the earlier one does.
The UC Cooperative Extension is emphatic on this point: soil temperature, not air temperature, governs warm-season crop performance. Purchase your tomato and pepper starts from the nursery when you see them available in March, but hold them in a frost-free location (a south-facing porch, a greenhouse, a sunny garage window) until soil conditions are right.
March Garden Tasks
Beyond planting, March brings a set of maintenance tasks that set the tone for the entire growing season.
Rose Pruning
If you grow hybrid tea roses, the traditional guidance is to prune when forsythia blooms — a phenological cue that translates roughly to late February through mid-March in most of Sonoma County. Cut back to outward-facing buds, remove crossing canes and deadwood, and open the center of the plant to air circulation. Modern shrub roses (David Austin English roses, for example) require lighter pruning than hybrid teas; remove approximately one-third of the previous year’s growth and shape for airflow rather than cutting hard to the base.
First Fertilizer Application
March is the appropriate time for the first fertilizer application of the year on established ornamental plantings, lawns, and fruit trees. Wait until you see active new growth before fertilizing — applying nitrogen to dormant plants risks leaching without uptake. For established fruit trees, a balanced granular fertilizer broadcast over the root zone (not piled at the trunk) and watered in is appropriate once leaf buds are actively swelling. For ornamental beds, a light application of a balanced, slow-release fertilizer in early March is appropriate.
Irrigation System Startup
March is the time to inspect, test, and bring irrigation systems back online before the dry season begins in earnest. Walk each zone. Look for cracked risers and emitters damaged by winter foot traffic or machinery. Check controller programming and update watering schedules to reflect spring (as opposed to summer) evapotranspiration rates — the UC ANR reference ET for Sonoma County in March is roughly half of peak summer demand. Over-irrigating in spring is as damaging to plant roots, and as wasteful of water, as under-irrigating in summer.
Mulching
Apply a 2 to 3-inch layer of wood chip mulch to established planting beds in March, before soil temperatures rise and weed seeds begin germinating en masse. Keep mulch pulled back 4 to 6 inches from the base of woody plants and trees to prevent crown rot. Wood chip mulch from a local arborist (often available free or at low cost in Sonoma County) is preferable to bagged decorative bark for most landscape applications: it breaks down slowly, feeds soil biology, and moderates soil temperature more effectively.
Dividing Perennials
Spring-blooming perennials that have finished their dormant period can be divided and replanted in March while soil is still moist and temperatures are cool. Agapanthus, daylilies, ornamental grasses, and Shasta daisies all benefit from division every three to five years. Dig the clump, split it with a sharp spade or pruning saw, and replant divisions at the same depth with good soil contact. Water thoroughly and keep divisions consistently moist through their first summer.
Zone-by-Zone Timing Guide for Sonoma County
Sonoma County spans a remarkable range of microclimates across a relatively compact geography. The Pacific Ocean drives much of this variation — maritime influence moderates temperatures in the western portions of the county, while the mountains east of Santa Rosa create warmer, drier conditions in the inland valleys. Understanding your specific zone is essential for accurate planting timing.
Coastal and Fog-Influenced Zones (Zone 9a): Sebastopol, Forestville, Bodega Bay, Western Petaluma
These areas experience the most moderate year-round temperatures, with cool summers and mild winters. Frost is rare but does occur; last frost dates typically fall in late February to early March. Soil temperatures in March tend to run 2 to 5 degrees cooler than inland valleys. Recommendations: delay warm-season crop planting until May; focus March planting energy on cool-season vegetables, natives, and Mediterranean ornamentals. Sweet peas, cool-season annuals, and brassica transplants all thrive here through late spring.
Interior Valleys (Zone 9b-10a): Healdsburg, Santa Rosa, Windsor, Cloverdale, Sonoma
The inland valleys warm earlier in spring and are subject to occasional late frost events through mid-March. Once past frost risk (typically by March 15 to 20 in most inland valley locations), the planting season accelerates quickly. Soil temperatures reach 55 to 60°F in late March in exposed, south-facing beds. Gardeners in these zones can push cool-season plantings aggressively in early March and begin hardening off tomato and pepper starts in late March for April planting.
Hilltops and Frost Pockets
Many Sonoma County properties sit at elevation or in topographic depressions where cold air pools on clear winter nights. These frost pockets can experience killing frosts weeks after valley locations have moved past frost risk. If your garden has experienced late frosts in April in previous years, treat your planting calendar conservatively — extend the caution period by two to three weeks beyond valley recommendations for all frost-sensitive crops.
Ready for a Spring Garden Overhaul?
Whether you’re adding raised beds, converting lawn to a productive garden, or just need a landscape maintenance refresh before summer — spring is the right time to start. We’ve been doing this in Sonoma County since 1983.
