It happens every single year right around March. The seed catalogs are stacked on the coffee table, the days are finally stretching out a little longer, and every gardener catches a serious case of “spring fever.” We start daydreaming of sweeping naturalistic borders, towering blooms, and the rich, earthy smell of damp potting soil.
That is, until we step outside, feel that sharp chill in the wind, and realize the garden is still very much asleep.
If that urge to get your hands dirty is driving you crazy, don’t stress; there is actually plenty of planting to do right now. In fact, it’s highly recommended that you get growing in March. There are a lot of breathtaking, slow-to-establish blooms that absolutely require this indoor head start to ensure a successful, early-blooming season—especially if you want to save a fortune by skipping the expensive, mature plants at the nursery later on.
Many of your favorite cottage garden showstoppers can—and should—be started indoors this month. Here are 15 flower seeds you need to sow right now to cure that spring fever and guarantee the most glorious garden on the block this year.
1. Carnations (Dianthus caryophyllus)
If you want those armfuls of ruffled, fragrant stems before Labor Day, March is your absolute deadline. I learned this the hard way after trying to direct sow in May and watching the plants collapse before they ever flowered. Now I start ‘Chabaud Mix’ and the clove-scented ‘Grenadin’ series indoors during the first week of March, not because they are fragile, but because they are painfully slow.
These perennial types need ten to twelve weeks of cool growing before they even think about budding, and by the time May rolls around, summer heat arrives before direct-sown plants can size up.
I keep them under lights or on a bright windowsill where nights stay cool, and I pinch the tips once at six inches to force bushier growth. Gardeners in Zones 7 and 8 can cheat with a cold frame in mid-March, but anyone north of Zone 6 should already have trays going. If you are in Zone 9 or warmer, you should have started in February or wait for fall, as carnations despise baking in ninety-degree soil.
2. Creeping Thyme (Thymus serpyllum)
The secret to a thyme path that can actually handle foot traffic without dying off is starting the seeds now, while the ground is still cold and weed competition is dormant. I surface-sow ‘Coccineus’ and the woolly-leaved Thymus pseudolanuginosus between my flagstones during the third week of March, pressing the seeds into the soil rather than burying them.
Thyme needs light to germinate and will rot if you plant it deeper than a dusting of soil. This timing is crucial for Zones 5 through 7, where soil temperatures around 50°F trigger germination and allow deep root establishment before summer drought stress hits.
If you are in Zone 4, wait until early April when the snowmelt has truly passed, but do not delay past tax season. Thyme started in May develops shallow, panicked roots that rarely survive the winter. By August, you will have those fragrant mats releasing that resinous Mediterranean scent every time you walk past, and the bees will thank you for the late-season nectar.
3. Delphinium (Delphinium elatum)
Nothing brings that show-stopping, vertical drama quite like Delphiniums (Delphinium elatum), but let’s be realistic—they can be absolute divas if you don’t treat them right from day one, which is why March is my absolute cutoff for getting them started.
I always pop the seed packet in the fridge for a week or two before planting to simulate winter, because they often need that cold stratification to even think about waking up. Once they do sprout, I keep them in a cool room under very strong grow lights so they don’t get leggy, and since they actually prefer cool weather, I transplant these out into the garden right around my last frost date.
They are incredibly heavy feeders, so before I put them in the ground, I dig a massive hole and mix in a hefty amount of rich compost, and I immediately put down slug bait because pests will devour them overnight. I personally stick with the ‘Pacific Giant’ series because you just can’t beat those intensely rich cobalt and sapphire blue spires that command attention from across the yard.
4. Blue Flax (Linum perenne)
I love sowing Blue Flax in March because it is one of the few flowers that actually prefers cold soil to warm. While most seeds are still sleeping, I scatter ‘Sapphire’ and ‘Bright Eyes’ directly into the garden the moment the soil can be crumbled in my fist, even if mornings still carry frost.
These seeds germinate at soil temperatures as low as 45°F, which means by late May you get that hazy blue mist hovering above fine green needles while your summer annuals are still stretching their legs. In Zones 4 and 5, I wait until late March when the frost heave has settled, keeping fleece handy for those erratic April dips. The seedlings are hardy but can get heaved out if you sow too early into freezing and thawing soil. Once established, this perennial will self-sow reliably in lean, well-drained spots, creating permanent drifts that return every spring without any fuss from you.
5. Feverfew (Tanacetum parthenium)
If you want that effortless, untamed look in your borders with almost zero maintenance, Feverfew (Tanacetum parthenium) is the ultimate workhorse, and kicking it off indoors in March guarantees I have beautifully bushy, flowering plants by early June. It’s one of the easiest perennials to start from seed, and while it readily self-seeds once established, getting a head start is especially helpful if you’re a northern gardener dealing with a short growing season.
I just press the seeds lightly onto the soil surface, as they need light to germinate, and they are wonderfully forgiving when it comes time to move them outside. Once the danger of hard frost is gone, I just harden them off for a few days and tuck them into the ground; they aren’t picky about soil and they handle the transition like champions.
I am completely obsessed with the ‘Tetra White’ variety because it produces these crisp, white, double-button blooms that look amazing swaying in the breeze and actually do a fantastic job of deterring pests away from my more sensitive plants.
6. Hollyhocks (Alcea rosea)
You simply cannot design an authentic cottage space without the towering architecture of Hollyhocks (Alcea rosea) backing it up, but the catch is that they are biennials, meaning they usually wait until their second year to flower. My favorite gardener’s cheat code is that if I start them indoors early in March, I can actually trick them into blooming this very first summer, which is a lifesaver for us in colder zones, whereas my friends in warmer Southern zones can often just direct sow them in late autumn.
The most critical thing I’ve learned is that Hollyhocks develop a long, stubborn taproot very quickly, so I never use shallow trays; I always start them in deep peat pots or specialized root trainers. When the soil has genuinely warmed up in late spring, I handle them with extreme care, planting the entire biodegradable pot directly into the back of my border so I don’t disturb that taproot at all. The ‘Chaters Double’ variety is a phenomenal option I plant every year, producing towering, sturdy stalks loaded with massive blooms that look exactly like ruffled silk all the way up the stem.
7. Red Campion (Silene dioica)
If you have a tricky, dappled spot and want to create a stunning designer shade garden, Red Campion (Silene dioica) is an absolute lifesaver, and getting it started indoors in March is the secret to seeing those vivid flowers this summer. While it’s a resilient woodland native that naturally loves a bit of shade, I always start the seeds early under my indoor lights because they can be a bit sluggish to wake up in cold, wet spring soil.
You want to sow them right on the surface of your seed starting mix because they absolutely need a little light to germinate, just gently pressing them in so they don’t wash away when you water. Once the danger of hard frost has passed, harden them off and tuck them into the edges of your beds or under your shrubs where traditional sun-lovers struggle. I am completely devoted to planting them because their bright, rosy-pink blooms act as a massive beacon for passing butterflies, and the dense foliage creates a perfect habitat for local wildlife, including hedgehogs foraging in the underbrush, capturing that authentic, naturalistic cottage vibe perfectly.
8. Cornflower (Centaurea cyanus)
I always make sure to get my cornflowers sown in March because they are one of those rare annuals that actually prefer cold soil to warm, and if you wait until May, they will bolt straight to seed without giving you those ruffled blue buttons you are after. I direct sow ‘Blue Boy’ and the nearly black ‘Black Ball’ into prepared drills during the third week of March, raking the soil to a fine tilth and scattering the seeds thinly because they germinate readily in soil temperatures as low as forty degrees.
In Zones 4 through 6, you can sow as soon as the ground can be worked, but in Zones 7 and 8, you need to get them in before the soil warms past sixty degrees or they will struggle. The key is that cornflowers develop deep taproots when started early, making them incredibly drought tolerant once established, whereas April sowings produce shallow-rooted plants that flop over at the first hot spell.
By late May, you will have those papery blue, pink, or burgundy blooms on stiff stems that last forever in the vase, and if you succession sow every two weeks through April, you will have flowers until August.
9. Verbena (Verbena bonariensis)
I used to think growing Verbena (Verbena bonariensis) from seed wasn’t worth the headache. The seeds take their sweet time, and the germination is notoriously spotty. But if you want those floating purple flower heads that look so good weaving through a naturalistic garden, March is your window.
Here’s the trick I finally learned: these seeds actually need darkness to wake up. Give them a light covering of soil, put them on a heat mat, and then just walk away for a few weeks. Don’t toss the tray when nothing happens right away! Once they finally sprout and the weather warms up past the frost dates—especially for folks in Zones 6 and below who have to treat them as annuals—you can get them out into the beds.
They have these incredibly tall, wiry stems that weave perfectly through heavier, drought-tolerant plants without shading them out. I usually stick to the standard species rather than the dwarf cultivars, simply because the tall ones bring in absolute hordes of butterflies and look the most authentic in a wild, cottage-style setting.
10. Black-Eyed Susan (Rudbeckia hirta)
A lot of gardeners skip starting Black-Eyed Susan (Rudbeckia hirta) indoors because they figure they’re tough enough to just throw in the dirt outside. And they are—but if you direct sow them in northern or midwestern zones, you might be waiting until late August to see a single flower.
I prefer to start mine in flats right now. The seeds are tiny, so whatever you do, don’t bury them. They need light to trigger germination, so just press them firmly into the damp potting mix. Let them build a solid root system indoors under your lights, then move them out in mid-spring once the soil is workable. They handle terrible soil and drought like a champion.
Instead of the usual yellow ones you see at every gas station, try hunting down the ‘Sahara’ mix. The colors are incredible—faded copper, mustard, and dusty rose—which completely elevates them from “roadside weed” to something you’d actually want to feature on a Pinterest board. Plus, if you leave the dark seed heads standing in the fall, the local songbirds will pick them clean.
11. Zinnia (Zinnia elegans)
Every old-school gardening book will tell you to never, ever start Zinnias (Zinnia elegans) indoors because they hate having their roots messed with. But if you live in a place with a short summer, or if you just want cut flowers before July, you can absolutely cheat the system.
The secret is to start them in late March using soil blocks or paper pots that can go straight into the ground. That way, the roots never even know they were moved. Don’t start them too early, though, or they’ll get leggy and sad on your windowsill; four weeks inside is plenty. Wait until your night temperatures are solidly in the 50s before planting the whole biodegradable pot outside.
I’m currently growing ‘Queen Red Lime’. The vintage, dusty pink and lime green color is so unique, it completely stops people in their tracks when they see it mixed into an American-style cottage border. Just give them full sun and plenty of airflow to prevent mildew, and you’ll be cutting them for the house until the first frost.
12. Red Campion (Silene dioica)
This woodland native is one of my favorite March sowings because it establishes so much better when given a cold start, and if you get it in now, you will have those vivid magenta flowers lighting up shady corners by next spring.
I sow ‘Alba’ (the white form) and the straight species directly into partial shade during mid-March, barely covering the seeds because they need light to germinate and will sit dormant if buried too deep. In Zones 4 through 6, this is the perfect time to scatter them along woodland edges or under deciduous shrubs where they will self-seed once established.
Gardeners in Zones 7 and 8 should sow now while the soil is still cool and moist; waiting until April often means the seeds dry out before they can establish. Red campion is technically a short-lived perennial that behaves like a biennial, so these March sowings will form tight rosettes of downy leaves this season and send up those glowing pink flowers on two-foot stems early next year, just when the garden needs that pop of color.
13. Ox-eye Daisy (Leucanthemum vulgare)
You simply cannot have a true, naturalistic meadow or a classic American home garden without the cheerful, familiar faces of the Ox-eye Daisy (Leucanthemum vulgare). I know they are incredibly vigorous self-seeders once they get going, but if you want that breathtaking drift of white blooms by early summer rather than waiting until fall, starting them indoors in March gives them the sturdy, drought-tolerant root system they desperately need.
The seeds are fairly small and require light to sprout, so I just sprinkle them lightly across a pre-moistened tray and gently press them in without burying them under any soil. They are incredibly tough plants, so you can safely transplant these out into your sunniest, most well-draining beds a week or two before your last frost date.
I always make a point to grow the ‘May Queen’ variety because it flowers exceptionally early, and those crisp, white petals with bright golden centers make the absolute perfect, long-lasting cut flowers, while also drawing in a huge array of beneficial songbirds who come looking for the seeds later in the season.
14. Sneezeweed (Helenium autumnale)
I know the name is unfortunate, but sneezeweed is actually one of the best late-season natives you can start now for autumn color that absolutely glows in the low light of September. I start ‘Moerheim Beauty’ and the shorter ‘Ruby Tuesday’ indoors in early March, barely covering the seeds because they need some light to germinate.
They are slow to get going, often taking two to three weeks to show any green, and they stay small and unimpressive until July, which tricks many gardeners into thinking they have failed. Do not give up on them. In Zones 3 through 5, you must start indoors to get blooms the first year.
In Zones 6 through 8, you could direct sow in late March, but the seedlings are tiny and easily swamped by weeds, so I prefer the controlled environment of a seed tray. By October, when everything else is fading, these March-started plants will be covered in russet and gold daisy-like flowers that last until the first hard frost and provide the last nectar for
15. Lobelia (Lobelia erinus)
March is non-negotiable for lobelia if you want those cascading clouds of sapphire blue spilling from your containers by late spring, because these are agonizingly slow in the seedling stage and will still be tiny in May if you start them then.
I sow ‘Crystal Palace’ with its dark bronze foliage and the trailing ‘Regatta’ series indoors during mid-March, barely pressing the dust-like seeds onto the surface of moist compost and never covering them, as they need light to germinate. I bottom water religiously because a watering can will wash these microscopic seeds into oblivion.
They need warmth to germinate, around seventy degrees, so I keep them on a heat mat until the green specks appear, which takes about two weeks. In Zones 8 through 10, you can sow directly in late March, but everyone else should start under cover.
The key is getting them established before summer heat hits, as they are cool-season annuals that will collapse in ninety-degree weather but will bloom beautifully from May through July if started now. By starting in March, you get those intense blue, white, or pink flower masses that cascade over pot edges and attract butterflies, exactly when the garden needs that cool color most.
Written By
Amber Noyes
Amber Noyes was born and raised in a suburban California town, San Mateo. She holds a master’s degree in horticulture from the University of California as well as a BS in Biology from the University of San Francisco. With experience working on an organic farm, water conservation research, farmers’ markets, and plant nursery, she understands what makes plants thrive and how we can better understand the connection between microclimate and plant health. When she’s not on the land, Amber loves informing people of new ideas/things related to gardening, especially organic gardening, houseplants, and growing plants in a small space.