Growing lemongrass from seed means starting indoors 10 to 12 weeks before your last frost, since the seeds need warmth around 75 to 85°F to germinate and the plant needs a long, hot stretch to bulk up before harvest. Sow seeds a quarter inch deep in a light seed-starting mix, keep them warm and moist, and expect germination in 10 to 25 days, sometimes slower and patchier than most herb seeds you have grown before. From there you are looking at a full season, often 4 to 6 months, before you have stalks worth cutting.
Here is the part almost nobody tells you going in: lemongrass seed is slow and uneven on purpose, and the seedlings look so much like grass for the first month that plenty of people pull them thinking they are weeds. That is the mistake that quietly ends most attempts before the plant ever gets a fair shot.
There is also a bigger honest answer waiting for you further down, about whether starting from seed even makes sense compared to rooting a grocery-store stalk, and I will give you that answer straight, not the cheerful non-answer you’ll find elsewhere. Stick with this and you will also get a save-able Lemongrass at a Glance card at the bottom with every number in one place.
When to Start Lemongrass Seeds
Lemongrass is a tropical grass, hardy only in zones 9 through 11, and everywhere else it is grown as an annual or overwintered indoors. That means your start date is not really about frost at all, it is about giving the plant enough hot months to size up.
Start seeds indoors 10 to 12 weeks before your last expected frost. Direct sowing outdoors works only if you already live somewhere with a long, consistently warm season, since the seed will not germinate reliably in cool soil.
If your springs run cool and short, indoor starting is not optional, it is the difference between a harvest and a houseplant that never gets there.
Sowing Lemongrass Seed Step by Step
The steps are simple, but lemongrass seed punishes sloppiness more than basil or cilantro would.
Step 1: Choose the medium
Use a light, well-draining seed-starting mix, not garden soil and not straight compost. Fill small pots or cell trays, since lemongrass resents having its roots disturbed later.
Step 2: Sow shallow
Press seeds onto the surface and cover with about a quarter inch of mix, no deeper. Buried too deep, these seeds simply rot before they sprout.
Step 3: Keep it warm
Soil temperature of 75 to 85°F is the real trigger here. A seedling heat mat earns its keep on this one crop specifically, since room temperature alone is often too cool.
Step 4: Light and moisture
Keep the mix evenly moist, never soggy, and give strong light once sprouts appear, ideally 12 to 14 hours under grow lights or a bright south window.
Get the warmth right and the rest mostly takes care of itself.
Germination: What to Expect, and When to Actually Worry
If you assumed slow germination means dead seed, that guess causes more wasted trays than any actual problem does. Lemongrass routinely takes 10 to 25 days, and germination is uneven, with some seeds up in a week and others taking three.
The sprouts themselves are the second trap. They emerge as thin, upright green blades that look exactly like crabgrass or a stray weed seed that hitchhiked in on the mix.
Do not weed your lemongrass tray. If you sowed lemongrass seed there and see grass-like sprouts in that exact spot, that is the crop, not a contaminant.
Real worry only sets in past the 4-week mark with zero sprouts at all, which usually points to soil that was never actually warm enough or seed that was old to start with.
Once you can tell the seedlings apart from weeds, the next test is whether they are strong enough to leave the tray.
Hardening Off and Transplanting
Lemongrass seedlings need to be a few inches tall with a couple of true blades before you even think about moving them outside. Rushing this step is the second big attempt-killer, right behind the weeding mistake.
Harden off over 7 to 10 days once nighttime temperatures are reliably staying above 55°F. Start with an hour or two of sheltered outdoor time and add an hour daily, watching for bleached or scorched blades, which means you pushed the sun too fast.
Transplant into the garden or into a large container, since lemongrass forms a substantial clumping base and shallow pots stunt it. Space plants 24 to 36 inches apart, they get wide, easily 3 to 4 feet across by late season.
Full sun is non-negotiable, at least 6 to 8 hours a day, in rich, well-draining soil.
Get them in the ground at the right spacing and the plant does most of the growing on its own from here.
Season-Long Care
Lemongrass is thirsty and hungry once it is established, nothing like the low-water herbs you may be used to. Water enough to keep soil consistently moist, especially through hot stretches, and feed every 4 to 6 weeks with a balanced fertilizer or a top-dress of compost.
In-ground plants in zones 9 through 11 can stay put year-round. Everywhere else, plan to dig up the clump before your first fall frost and overwinter it in a pot indoors near a bright window, since a hard frost kills the plant outright.
Container-grown lemongrass dries out faster than in-ground plants, so check the top inch of soil daily during summer heat rather than sticking to a schedule.
Now for that honest answer I promised: starting from seed gives you named varieties and a real sense of accomplishment, but rooting a stalk from the grocery store gets you to a harvestable clump months faster, since you skip the slow, uneven germination stage entirely. Seed is worth it if you want variety options or simply enjoy growing from scratch, not because it is the faster or easier route.
Whichever way you started, the next question is always the same one: how do you know it is finally ready to cut.
When Lemongrass Reaches Harvest
Lemongrass is ready to start harvesting once stalks are at least 12 inches tall and about a half inch thick at the base, usually 4 to 6 months after sowing if it had a genuinely warm, sunny season. The base of the stalk turns pale yellow-green and feels firm and fibrous, almost woody, when you pinch it.
Harvest by cutting individual stalks at ground level or by twisting and pulling the outer stalks away from the clump, leaving the center to keep growing. Take outer stalks first, always, so the plant keeps producing from the middle.
Lemongrass rarely flowers in cultivation outside its native tropical range, so do not wait around for a bloom as your signal, thickness and that pale, fibrous base are what matter.
Once you’ve cut your first stalk and caught that bright citrus smell off the crushed base, you’ll understand why people keep growing this one despite the slow start.
Lemongrass at a Glance
- When to plant: start seeds indoors 10 to 12 weeks before your last frost, transplant outdoors once nights stay above 55°F.
- Germination needs: soil temperature of 75 to 85°F, seeds sown a quarter inch deep, sprouting in 10 to 25 days.
- Light: full sun outdoors, at least 6 to 8 hours daily, and 12 to 14 hours under grow lights while seedlings are indoors.
- Spacing: 24 to 36 inches apart, since mature clumps spread 3 to 4 feet wide.
- Water and feeding: keep soil consistently moist, feed every 4 to 6 weeks once established.
- Hardiness: perennial only in zones 9 through 11, grown as an annual or overwintered indoors elsewhere.
- Harvest window: 4 to 6 months from sowing, once stalks are 12 inches tall, half an inch thick, and pale yellow-green and firm at the base.
The seeds are slow and the seedlings look like weeds, but neither one means you failed. Give lemongrass heat, sun, and patience, and it will hand you stalks worth cutting by summer’s end.
