March is the month that fools you. The light comes back fast — noticeably longer days by mid-month — but the soil is still cold, the nights still drop, and the plants that wintered indoors are sitting in a kind of suspended animation, waiting for a signal that it's safe to move again. Across the Pacific Northwest, March looks different depending on where you are: in Zone 9a on the BC Sunshine Coast or the Oregon coast, you may already have crocuses and early blossom. In Zone 7b in the Willamette Valley or coastal Washington, you're a week or two behind. In Zone 6b in the BC or Washington interior, you may still have frost on the ground. The question I get most often this time of year is some version of: what should I actually be doing right now? The honest answer is: more than most people think, and less than the gardening calendar usually suggests.
Indoors: The Plants That Wintered Over
Read the Light First
Before you do anything else, look at where your indoor plants are sitting and compare it to where they were in December. The sun angle has shifted dramatically. A plant that was getting adequate light in a south window in January is now getting significantly more — and plants that were just barely surviving in a dim corner may suddenly have enough light to start pushing new growth. Move things around if you need to. A plant that's been dormant all winter and suddenly gets March sun on it will start waking up, and you want to be ready for that.
Resume Watering — Carefully
The number one mistake people make in March is overwatering plants that are just starting to come out of dormancy. The roots are not yet active enough to process a lot of water. I check soil moisture by feel — a finger two inches into the soil — before I water anything. If it's still damp, I wait. If it's dry, I water thoroughly and let it drain completely. No sitting water in saucers. That's true all year, but it matters more now when root systems are just waking up.
Repot If You Need To — But Not Yet for Everything
March is the right time to repot plants that have been root-bound since last summer, because they're about to enter a growth phase and fresh soil will make a real difference. I look for roots coming out of the drainage holes, or a plant that dries out within a day or two of watering — those are the ones that need a new home. Go up one pot size, not two. A pot that's too large holds too much moisture around roots that aren't yet active enough to use it.
The Case for a Foliar Spray Right Now
Kelp extract applied as a foliar spray in early spring is one of the most effective things you can do for indoor plants coming out of winter dormancy. The mechanism is well-documented in the literature. Saccharina and other brown kelps contain naturally occurring cytokinins — plant hormones that signal cell division and delay senescence. When you apply a fermented kelp spray to the leaves, the plant absorbs those cytokinins directly through the stomata and leaf cuticle. The result is a measurable increase in the rate at which the plant breaks dormancy, pushes new growth nodes, and begins photosynthesising at full capacity.
Cytokinins also interact with auxins — the hormones that govern root elongation — in a way that promotes balanced above-ground and below-ground growth. A plant that's been sitting in the same pot all winter with depleted, compacted soil is often auxin-deficient at the root tips. A foliar application of fermented kelp doesn't just feed the leaves; it sends a hormonal signal that wakes up the whole system.
I use my foliar spray on indoor plants every two weeks starting in early March, misting the undersides of leaves as well as the tops. Early morning is best — the stomata are most open then, and the liquid dries before any fungal issues can develop. The plants I notice responding most visibly: monstera, pothos, ficus, citrus, and any herbs that have been struggling through the winter. Orchids respond well too — I've seen a noticeable difference in new root tip development after a few weeks of regular foliar application.
Start Seeds Under Lights
If you're starting tomatoes, peppers, or eggplant from seed, March is the time — six to eight weeks before your last frost date. In Zone 9a (Sunshine Coast, Portland, Seattle metro), last frost is typically late February to mid-March, so you may already be at the window. In Zone 8a (Willamette Valley, coastal Washington, Victoria), last frost is mid-March to early April — start seeds now. In Zone 7a (inland Washington and Oregon, Okanagan), last frost is late April, so you have more runway. In Zone 6b (BC and Washington interior), last frost can run into mid-May — start seeds in late March or early April. I start seeds under a simple LED grow light on a timer, 16 hours on, 8 off. Once seedlings have their first true leaves (not the seed leaves — the second set), I begin foliar spraying with a diluted kelp solution. The research on this is consistent: seedlings treated with seaweed extract at the cotyledon stage show significantly better root mass and shoot development than untreated controls.
Outdoors: The Garden in March
Soil Temperature Is the Real Signal
The calendar says spring. The soil doesn't care about the calendar. I use a cheap soil thermometer and check at 10cm depth — that's the number that matters, not the date. In Zone 9a on the BC Sunshine Coast or Oregon coast, soil temperatures in early March are typically 5–8°C. In Zone 8a (Willamette Valley, coastal Washington), expect 4–7°C. In Zone 7a (inland Oregon and Washington), 3–6°C. In Zone 6b (BC and Washington interior), soil may still be at or near freezing in early March. When it hits 7°C consistently, cool-season crops can go in. When it hits 10°C, you're in business for most things.
What Can Go In Now
Garlic that you didn't plant in fall can still go in now — it'll be late, but it'll produce. Peas, spinach, kale, arugula, and overwintering onion sets can all be direct-sown in March across most of the Pacific Northwest. Broad beans too. These crops actually prefer cool soil and will stall out if you wait until it warms up. In Zones 8b–9a, all of these can go in by early March. In Zone 8a, mid-March. In Zone 7, wait for late March or early April when soil is reliably above 5°C. In Zone 6b, hold off until April.
Perennials are waking up across the PNW. This is the time to divide hostas, daylilies, and ornamental grasses before they get too far along. Cut back last year's dead growth on ornamental grasses and perennials — but leave the crowns alone until you can see new growth emerging.
The Root Drench: Why March Is the Right Time
A kelp root drench applied in early spring, before active growth begins, is one of the highest-leverage applications you can make in the entire gardening year. The root zone in March is just beginning to warm. Microbial activity in the soil — the bacteria and fungi that make nutrients available to plant roots — is ramping up from its winter low. Kelp extract, particularly the polysaccharides like laminarin and fucoidan found in Saccharina, acts as a prebiotic for soil microbes. It feeds the microbial community, which in turn makes phosphorus, nitrogen, and trace minerals more bioavailable to plant roots as they begin to grow.
There's also a direct hormonal effect. The auxins in fermented kelp extract applied as a soil drench have been shown in multiple studies to stimulate root elongation and lateral root formation — the fine root hairs that do most of the actual nutrient uptake. Getting that root development happening early, before the plant is under the stress of full growth, sets up a much stronger plant for the rest of the season.
I apply the root drench to my raised beds, my perennial borders, and around the base of any shrubs or fruit trees in early March — before I see significant new growth. I pour it directly into the root zone, about 250mL per square metre, undiluted. I do a second application in late April or early May when growth is actively underway.
Fruit Trees and Shrubs
March is the last call for dormant pruning of fruit trees across the Pacific Northwest. Get it done before the buds break open — in Zone 9a this means early March, in Zone 8a mid-March, in Zone 7 late March, in Zone 6b you have until early April. Once you've pruned, a root drench around the drip line (the outer edge of the canopy, where the feeder roots are) is genuinely useful — the auxins in the kelp extract support the callusing and healing of pruning wounds, and the cytokinin activity helps push even bud break across the canopy.
Blueberries, currants, and gooseberries can all be pruned now and will benefit from a root drench immediately after. Raspberries: cut last year's canes to the ground, leave the new green canes, and drench.
A Simple March Schedule
The way I think about it: two things, two weeks apart. Adjust the timing based on your zone — Zone 9a growers can run this schedule as written; Zone 8a growers push everything one to two weeks later; Zone 7 growers push two to three weeks; Zone 6b growers push three to four weeks.
First week of March (Zone 9a) or adjusted start: Foliar spray all indoor plants. Apply root drench to outdoor beds, fruit trees, and shrubs. Repot anything root-bound. Start tomato and pepper seeds under lights.
Third week of March (Zone 9a) or adjusted: Second foliar spray on indoor plants. Direct sow peas, spinach, kale, and arugula outdoors. Divide perennials. Begin hardening off any seedlings that are getting ahead of themselves.
That's it. March doesn't need to be complicated. The plants are doing most of the work — you're just making sure they have what they need to do it well.
Gerald has been fermenting seaweed on the Pacific Northwest coast for 25 years. He runs Just Gerald Seaweed Company out of Roberts Creek, BC. Orders: [email protected]
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