Hydroponic lemongrass starts with a trip to the grocery store. The stalks sold for cooking often still have a living base, and stood in water, a good one puts out roots within 2 to 6 weeks. Roughly two out of three firm, fresh stalks take. Move the rooted stalks into a nutrient solution, give them warmth and light, and in 2 to 4 months you are cutting your own stalks for soups and curries.
There is a catch worth knowing before you start. Lemongrass is a big plant. A clump reaches 2 to 4 feet indoors, wants 3 to 5 gallons of water, and has no dwarf variety. So the realistic apartment plan is not a permanent jar on the windowsill. It is rooting grocery stalks for a run of short-term harvests, and moving to a bigger container, or outdoors, if you want a clump that lasts. This guide covers both. If hydroponics is new to you, the apartment hydroponics beginner’s guide explains the basics.
Hydroponic Lemongrass at a Glance
Key takeaways
- Buy stalks with firm, intact bases, no mold and some green at the top. They root in water in 2 to 6 weeks, and about two in three succeed.
- Once rooted, grow them in a DWC container of 3 to 5 gallons with 3 to 4 inch net cups. A quart jar is too small.
- Lemongrass likes a higher pH than most herbs: 6.0 to 7.0, with 6.3 to 6.5 as the target. Feed rooted stalks at EC 1.6 to 2.4.
- Keep it warm, with the room at 70 to 85°F and the water at the warm end of 65 to 75°F, and give it 14 hours of light.
- Harvest after 2 to 4 months, once stalks are 12 inches tall and half an inch thick at the base.
The Numbers for Lemongrass
Every figure here comes from the crop table this site uses for lemongrass.
| Setting | Lemongrass | Why it matters |
|---|---|---|
| Difficulty | Intermediate | Easy to root, although slow, large and hungry for water volume |
| pH | 6.0 to 7.0, target 6.3 to 6.5 | Higher than most herbs, since it struggles below 6.0 |
| Feed strength (EC) | 0.8 to 1.0 for new roots, 1.6 to 2.4 once growing | A medium feeder, so thin pale stalks usually mean underfeeding |
| Light | 14 hours on, 10 off, 6 to 8 inches above the leaves | When the light is weak, stalks grow thin |
| Light intensity | 150 to 200 PPFD while rooting, 200 to 250 once growing | It tolerates much brighter light too |
| Water temperature | 65 to 75°F (18 to 24°C), the warm end suits it | More heat tolerant than any other crop on this site |
| Room | 70 to 85°F (21 to 29°C) | It likes humidity but tolerates household levels |
| Container | DWC, 3 to 5 gallons per clump, 3 to 4 inch net cups | Because it is unsuitable in a quart jar and marginal in a gallon |
| Timeline | Roots in 2 to 6 weeks, first harvest after 2 to 4 months | Wait for 12 inch stalks half an inch thick |
Choosing Grocery Stalks That Will Root
Success is mostly decided in the shop. A stalk roots from the growing point at its base, so that base has to be intact and alive. Check each one before you buy:
- A firm, plump base that has not been trimmed flat. Any remnant of old roots is a bonus.
- No mold, soft patches or sour smell at the bottom.
- Some green left at the top, a sign the stalk is still fresh.
- As fresh as you can find. Stalks that have sat in a cold room for days or dried out root poorly or not at all.
Asian groceries often have the freshest stalks, sold in bundles. Buy more than you need, because only about two in three root even when they are good ones, and use the rest in the kitchen.
Rooting Lemongrass in Water
Rooting is simple: the stalks stand in a little water until roots appear, which takes 2 to 6 weeks.
- Peel away any dry, papery outer layers at the base and trim the top of the stalk to leave a few inches of green.
- Stand the stalks in a glass or jar with an inch or two of plain water covering the base.
- Put the jar somewhere warm and bright, out of harsh direct sun.
- Change the water every few days, because stagnant water is what rots the bases.
- Throw out any stalk that turns slimy or moldy at the bottom, before it spoils the water for the rest.
Small white roots appear at the base first, followed by new green shoots from the center. Wait until the roots are an inch or two long before moving the stalk into a hydroponic setup. Warmth speeds all of this up, since lemongrass is a tropical grass that sulks in a cool room.
Tip. Once roots appear, you can add a weak feed to the rooting jar, at EC 0.8 to 1.0 and pH around 6.3. Plain water starts roots, but a stalk sitting in it for weeks has nothing to grow on.
Growing the Rooted Stalks Hydroponically
A rooted stalk needs room. Lemongrass is unsuitable in a quart jar and only marginal in a gallon, because it grows big and drinks a lot. For stalks you plan to harvest over several months, use a DWC container of 3 to 5 gallons with an air stone, and 3 to 4 inch net cups.
- Set each rooted stalk in a net cup, with clay pebbles packed around the base to hold it upright.
- Fill the container until the solution covers the bottom of the cups, so the new roots reach it on day one.
- Run the air stone day and night, and let the level sit a little below the cups as roots grow down.
- Top off daily with plain pH-adjusted water, never with nutrients, and change the whole reservoir every 2 weeks.
Several stalks can share one container if you are harvesting them young, spaced about 12 inches apart. The air pump hums, so stand it on a folded towel; the quiet air pump roundup compares the quiet ones, and the quiet DWC bucket build shows a full setup. Reusing clay pebbles covers the medium.
pH and Feeding
Lemongrass prefers a higher pH than most herbs. Hold it at 6.0 to 7.0, and aim for 6.3 to 6.5. Below 6.0 it struggles, so a reservoir run at the low end like a basil jar is too acidic for it. That also means it does not share a tank well with most herbs. The pH and nutrient calculator helps you hold the higher target, and why pH keeps drifting explains the usual wobbles.
Feed new roots gently, at EC 0.8 to 1.0, and once the stalk is growing well, raise it to 1.6 to 2.4. Lemongrass is a medium feeder. Thin, pale stalks usually mean it is underfed, while too much nitrogen gives lush leaves with less of the lemony aroma you want. There is no special need for Cal-Mag. Mixing two-part nutrients shows the method, and a decent EC meter and pH meter keep both numbers honest.
Light and Warmth
Give lemongrass 14 hours on and 10 off, with the panel 6 to 8 inches above the leaves. It needs about 150 to 200 PPFD while rooting and 200 to 250 once growing, and it tolerates much brighter light, so a sunny spot plus a lamp is fine. Thin, weak stalks under a light usually mean the light is too far away, or the feed too low. The grow light calculator checks your fixture, and a plug-in timer from the compact timers roundup keeps the 14 hours honest.
Warmth matters more for lemongrass than for any other crop on this site. It is happiest with the room at 70 to 85°F (21 to 29°C), and it is more heat tolerant than everything else you might grow. Keep the water within 65 to 75°F (18 to 24°C), toward the warm end, with the air stone running, since warm water still holds less oxygen. In a cold winter flat it slows almost to a stop, so give it the warmest bright spot you have. Small system temperature covers both extremes.
Harvesting Lemongrass
Wait 2 to 4 months after rooting, until stalks are about 12 inches tall and half an inch thick at the base. Harvest too early and you get thin stalks with little flavor.
- Choose the thickest outer stalks.
- Snap or cut each one 1 to 2 inches above the root crown, so the base keeps sending up new shoots.
- Take stalks one at a time as you need them, and leave the younger ones growing.
Lemongrass tastes of citrus and lemon with a mild ginger undertone. The pale lower stalk is the part used in Thai and other Asian cooking. It holds up to long simmering and is usually infused rather than eaten, so bruise it and pull it out before serving. Freshness matters more than variety: the fresher the stalk, the stronger the flavor. The seed to harvest calculator can help you track when a batch should be ready.
The Size Problem, and What to Do About It
Lemongrass does not stay small. A clump reaches 2 to 4 feet indoors, and up to 6 in ideal conditions, and a full clump needs 2 to 3 feet of space around it. No dwarf variety exists. One clump can be a handsome feature plant in a bright corner. Several will take over the room.
So plan in one of two ways. For a short-term supply, keep rooting a few fresh grocery stalks every couple of months, harvest them young, and start again. For a lasting clump, move a well-rooted plant into the largest container you have, 5 gallons, or plant it outdoors or on a balcony for the warm months if you have one. Either way, the small-jar version most guides show is not how it goes. If space is tight, the best herbs for small hydroponics lists compact alternatives.
Note. The ASPCA lists lemongrass as toxic to cats and dogs, causing stomach upset. Its grassy leaves are exactly what cats like to chew, so keep it out of reach if you share your home with one. The same goes for the nutrient bottles, as hydroponic nutrients and pet safety explains.
Where these facts come from
🔗 Where these numbers come from
The pH, EC, light, temperature, container and timeline figures here are the ones the crop table on this site uses for lemongrass, and the crop sources page lists the research behind each. Utah State Extension’s lemongrass guide covers the plant, and the UC Small Farms Network article covers growing it. The seedling feed is general herb practice, the light figures come from grower guidance, and the light height in inches is this site’s starting point for a typical home LED.
Troubleshooting Hydroponic Lemongrass
Most lemongrass problems happen in the rooting jar or come from a feed that is too weak.
| What you see | Most likely cause | What to do |
|---|---|---|
| Bases rotting in the rooting jar | Stagnant water | Change the water every few days and also discard moldy stalks |
| Stalks never root | Bases trimmed off or dried out before you bought them | Choose firm, intact bases with some green next time |
| Thin, weak stalks | EC too low, or the light too weak | Raise the EC toward 1.6 to 1.8 and keep 14 hours of light |
| Pale, yellowing leaves | pH below 6.0, or chronic underfeeding | Raise the pH toward 6.3 to 6.5 before you add feed |
| Lush leaves with little aroma | Too much nitrogen | Switch to a balanced feed so the stalks firm up |
| Growth almost stops | A cold room, especially in winter | Move it to the warmest bright spot, since it wants 70 to 85°F |
Rot in the Container
Once growing in a bucket, lemongrass roots are fairly tough, but warm, still water can still rot them. Healthy roots are white and firm. Brown, slimy roots with a stagnant smell need action: make sure the air stone is running, trim dead roots, and change the solution. For an active infection, add 3 ml of 3% hydrogen peroxide per liter; hydrogen peroxide for root rot explains how. Preventing root rot covers keeping it away, and why hydroponic plants turn yellow sorts out leaf color problems.
One Last Tip
Freeze your harvest rather than letting stalks sit. Lemongrass loses its fragrance fast once cut, and a few stalks in the fridge drawer are limp and dull within a week. Cut the stalks into short lengths, bruise them lightly, and freeze them in a bag. They go straight from the freezer into a pot of soup, and they keep their aroma far better than fresh stalks forgotten in the fridge. It also means you can cut the whole batch at its best instead of rationing it.
Frequently Asked Questions
Can I grow lemongrass from a grocery store stalk?
Yes. Choose stalks with firm, intact bases, no mold and some green at the top, and stand them in a little water. Roots appear in 2 to 6 weeks, and about two in three good stalks succeed. Change the water every few days so the bases do not rot.
How long does hydroponic lemongrass take to harvest?
Rooting takes 2 to 6 weeks, then the first harvest comes 2 to 4 months later, once stalks are about 12 inches tall and half an inch thick at the base. Harvesting earlier gives thin stalks with little flavor.
What pH and EC does lemongrass need?
Hold the pH at 6.0 to 7.0, aiming for 6.3 to 6.5, which is higher than most herbs; it struggles below 6.0. Feed new roots at EC 0.8 to 1.0 and growing stalks at 1.6 to 2.4. Thin, pale stalks usually mean the feed is too weak.
Can lemongrass grow in a mason jar?
Only while it roots. Lemongrass is unsuitable in a quart jar and marginal in a gallon, because it grows 2 to 4 feet tall and drinks a lot. Once rooted, move it into a DWC container of 3 to 5 gallons with 3 to 4 inch net cups and an air stone.
Why are my lemongrass stalks rotting in water?
The water is going stagnant. Change it every few days while the stalks root, keep only an inch or two of water over the base, and throw out any stalk that turns slimy or moldy so it does not spoil the rest. Stalks that were old or dried out when bought also rot instead of rooting.
How big does indoor lemongrass get?
A clump reaches 2 to 4 feet indoors, and up to 6 in ideal conditions, and a full clump needs 2 to 3 feet of space. There is no dwarf variety. For a small flat, root grocery stalks for short-term harvests, or move one clump to a large container or outdoors.
How much light does hydroponic lemongrass need?
Give it 14 hours on and 10 off, with the light 6 to 8 inches above the leaves. It needs about 150 to 200 PPFD while rooting and 200 to 250 once growing, and it tolerates brighter light. Thin, weak stalks often mean the light is too far away.
What temperature does lemongrass like?
It is a tropical grass and likes a warm room, 70 to 85°F, more heat tolerant than any other crop on this site. Keep the water at the warm end of 65 to 75°F with an air stone running. In a cold winter flat it slows almost to a stop.
Is lemongrass safe for cats?
No. The ASPCA lists lemongrass as toxic to cats and dogs, causing stomach upset. Its grassy leaves attract cats in particular, so grow it somewhere your pet cannot reach, and call your vet if a pet eats a lot of it.
How do I harvest lemongrass without killing the plant?
Snap or cut the thickest outer stalks 1 to 2 inches above the root crown, one at a time as you need them. The base keeps sending up new shoots. Leave the younger stalks to grow on until they reach about 12 inches and half an inch thick.
