Hydroponic shiso is one of the most rewarding herbs you can grow indoors, and one of the least understood. Also called perilla, it has a flavor nothing else on the shelf matches: mint, basil, anise and a hint of cumin in one broad leaf. Once it gets going it is resilient and bushy, and a single plant gives leaves every few days for weeks.
It has two quirks that trip up almost everyone. The seed is slow and stubborn unless you soak it first. And shiso is a short-day plant: it starts to flower as soon as the days get short enough, and 14 hours of light, the schedule most herbs on this site use, is short enough to set it off. So shiso runs on 16 hours. Get those two things right and the rest is straightforward. If hydroponics is new to you, the apartment hydroponics beginner’s guide covers the basics.
Hydroponic Shiso at a Glance
Key takeaways
- Soak the seed for 24 hours before sowing. Soaked seed sprouts in 4 to 7 days, dry seed in 7 to 21.
- Run the light 16 hours on and 8 off, because shorter days push shiso to flower early. Give it its own light where you can.
- Hold the pH at 5.8 to 6.2 and feed at EC 0.8 to 1.0 for seedlings, and later 1.0 to 2.0.
- A 1 gallon Kratky container works, although a DWC setup of 2 to 3 gallons is better for a full plant.
- First harvest is 8 to 10 weeks from seed. Pinch above a leaf node when plants reach 6 inches, and never take more than a third.
The Numbers for Shiso
Every figure here comes from the crop table this site uses for shiso, and harvest times count from sowing.
| Setting | Shiso | Why it matters |
|---|---|---|
| Difficulty | Easy but slow | Germination needs care, although the plant is tough once established |
| pH | 5.8 to 6.2, target 6.0 | It tolerates roughly 5.5 to 6.5, but grows best near 6.0 |
| Feed strength (EC) | 0.8 to 1.0 seedling, 1.0 to 2.0 growing | A light to medium feeder, so pale, slow growth means underfeeding |
| Light | 16 hours on, 8 off, 6 to 8 inches above the leaves | Shorter days make it flower instead of making leaves |
| Light intensity | About 300 PPFD | Especially for red shiso, which responds to brighter light |
| Water temperature | 65 to 75°F (18 to 24°C) | It dislikes extremes, while seed sprouts best near 68°F |
| Room | 65 to 77°F, humidity 40 to 60 percent | Stress sets in, however, above about 90°F |
| Container | Kratky in 1 gallon, or DWC of 2 to 3 gallons, 2 to 3 inch cups | Since it gets big, a quart jar is only marginal |
| Size | A foot to 18 inches tall when pinched, 8 to 10 inches apart | Unpinched, though, it reaches 18 to 30 inches |
| Timeline | Soaked seed sprouts in 4 to 7 days, first harvest at 8 to 10 weeks | When the lamp is strong, the first small picks can start at about 6 weeks |
Green or Red Shiso?
Shiso comes in two main forms. Green shiso, called aojiso in Japanese, has bright green, slightly milder leaves and is the one served with sushi. Red shiso has purple leaves, a slightly more astringent taste, and is used to color pickles such as umeboshi.
For a beginner growing for volume, green is the better choice by a wide margin. Under identical conditions green shiso has produced 58 to 270 percent more growth than red. The two also respond to different things: green shiso reacts more to feed strength, while red reacts more to light intensity, so red rewards a brighter lamp. Grow green first. Add a red plant later if you want the color.
Getting Shiso Seed to Sprout
Shiso seed has a reputation for poor germination, and most of it comes from sowing it dry. Dry seed takes 7 to 21 days and comes up patchily. Soaked seed sprouts in 4 to 7 days.
- Soak the seed in room-temperature water for 24 hours.
- Soak rockwool cubes in water adjusted to pH 5.5, deliberately low because the cube pulls the pH up.
- Shake the cubes to drain them, without squeezing, before you sow two or three soaked seeds on each.
- Keep the tray covered with a dome, and keep the seed moist, because letting it dry out after soaking undoes the work.
- Keep the tray near 68°F (20°C), where shiso sprouts best.
- When seedlings are up, take the dome off and put them under the light, 10 to 12 inches above them, with the feed at EC 0.8 to 1.0.
Thin each cube to the strongest seedling once it has its first true leaves. Starting seeds in rockwool covers the method and how to avoid damping-off, and the seed starting kit roundup compares domes and trays.
Why Shiso Needs 16 Hours of Light
Shiso is a short-day plant. It decides to flower when the nights get long enough, and the day length that triggers it sits close to the 14 hours most herbs on this site run. Under a 14 hour schedule, shiso flowers sooner, the leaves get smaller, and the plant starts winding down. Under 16 hours on and 8 off, it stays leafy and keeps producing. That is why shiso is one of the few crops here that runs 16 hours.
Hang the light 6 to 8 inches above the leaves, and aim for about 300 PPFD, more for red shiso. Treat the inches as a starting point for a typical home LED. Stretched stems with long gaps between leaves mean the light is too far away or too weak, while bleached leaves mean it is too close. The grow light calculator checks your fixture, and grow light distance for herbs covers the adjustment.
Sharing a Light With Other Herbs
One light runs one schedule, which is the awkward part. Basil, parsley and most leafy herbs run 14 hours, while shiso wants 16. Give shiso its own small light and timer if you can; a clip-on or a small bar is enough for one or two plants. Under a shared 14 hour panel it will still grow, but it will flower sooner and you will spend more time pinching off flower spikes. Stevia and nasturtium run 16 hours too, so they make good shelf-mates for shiso under a second light. A timer from the compact timers roundup makes the second schedule easy, and shelf layouts for one light shows how to plan a shelf.
The Right Container
Shiso reaches 12 to 18 inches when you keep it pinched, and up to 30 inches if you do not, so it needs more water than a small herb. A quart jar is only marginal. A 1 gallon Kratky container suits it, and a DWC setup of 2 to 3 gallons with an air stone suits a full plant for months. Use 2 to 3 inch net cups, and space plants 8 to 10 inches apart in a shared tote.
In a Kratky container, start with the bottom of the net cup in the solution, about half an inch to an inch deep, and let the level fall as the plant drinks. An air gap forms by itself, and shiso needs it: waterlogged roots with no air are its biggest weakness. Do not top it off every day, and never refill it to the brim. If it runs low, add a little nutrient solution, raising the level by no more than about an inch. In DWC, top off daily with plain pH-adjusted water and change the reservoir every 2 weeks. The Kratky jar setup guide and DWC vs Kratky cover both.
pH and Feeding
Hold the pH at 5.8 to 6.2 and aim for 6.0, the figure plant-factory research uses. Shiso tolerates roughly 5.5 to 6.5, but it grows best near the middle. Feed seedlings at EC 0.8 to 1.0, one of the few crops on this site that starts below 1.0, and raise established plants into 1.0 to 2.0.
Shiso is a light to medium feeder. Pale, slow growth means it is underfed, while too much nitrogen gives large, soft leaves with less aroma. There is no special need for Cal-Mag beyond what your water calls for. The pH and nutrient calculator works out doses, mixing two-part nutrients shows the method, and a good EC meter keeps you in range.
Temperature
Keep the room at 65 to 77°F with humidity at 40 to 60 percent, and the water at 65 to 75°F (18 to 24°C). Shiso dislikes extremes and gets stressed above about 90°F. Above 72°F (22°C) in the water, aeration matters more, and never cool a container with ice, since the sudden cold shocks the roots. A frozen bottle against the outside works better. Small system temperature fixes has more ideas.
🌱 Plan this grow: The free Urban Hydro grow planner turns these numbers into a day-by-day care list for your shiso, with a harvest date and reminders. It runs in your browser, and an account is optional.
Pinching and Harvesting
The first proper harvest comes 8 to 10 weeks from seed, and under strong light you can take a few leaves from about 6 weeks. Shiso is a cut-and-come-again herb, and the way you pick it decides how bushy it gets.
- When the plant reaches 6 inches, pinch or cut the stems just above a leaf node. Two new shoots grow from that point.
- Pick the outer, larger leaves first, while the growing tips keep producing.
- Harvest every few days to weekly.
- Never take more than a third of the plant at once, so it can recover.
Pinch off flower spikes as soon as you see them. Once shiso sets flowers, leaf production slows, and the leaves turn smaller and tougher. Regular pinching keeps the plant compact and full of leaves for many weeks. How to prune hydroponic herbs shows where to cut, and the principle is the same as for basil.
Use shiso fresh. It is wrapped around sushi, torn into salads, shredded over rice and noodles, and used in pickles. Green shiso is milder and the more versatile of the two. The seed to harvest calculator gives you a likely first-harvest date from your sowing day.
Where these facts come from
🔗 Where these numbers come from
The pH, EC, light, container and harvest figures here are the ones the crop table on this site uses for shiso, and the crop sources page lists the research behind each, including the short-day response and the green versus red growth comparison. Johnny’s shiso growing information covers germination and soaking. No separate water temperature is documented for shiso, so 65 to 75°F is the general range, and the light height in inches is this site’s starting point for a typical home LED.
Troubleshooting Hydroponic Shiso
Most shiso problems are germination, light or wet roots.
| What you see | Most likely cause | What to do |
|---|---|---|
| Seed barely sprouts | Not soaked, or allowed to dry after soaking | Soak 24 hours, sow on moist medium, and keep it covered until it sprouts |
| Leggy, weak stems | Too little light, or plants too crowded | Keep 16 hours at 6 to 8 inches and also thin to 8 to 10 inches |
| Sudden wilting | Root rot, when the roots sit waterlogged | Restore the air gap and also improve aeration |
| Early flower spikes and small leaves | Days too short, especially on a 14 hour schedule | Move it to 16 hours and also pinch off the flowers |
| Pale, slow growth | Underfeeding | Raise the EC gradually until it sits in 1.0 to 2.0 |
| Large, soft leaves with weak aroma | Too much nitrogen | Switch to a balanced feed so that the leaves firm up |
Root Rot and Waterlogging
Shiso hates roots sitting in water with no air. In a Kratky container, that happens when the level is topped back up to the cup; in DWC, when the air stone stops or the water runs warm. Healthy roots are white. Brown, slimy roots with a stagnant smell need action: restore the air gap or the aeration, trim dead roots, and refresh the solution. For an active infection, add 3 ml of 3% hydrogen peroxide per liter, as hydrogen peroxide for root rot explains. Preventing root rot covers keeping it away.
Aphids and Spider Mites
Shiso’s soft new growth attracts aphids, and dry rooms bring spider mites. Check the undersides of leaves weekly. Aphids wash off at the sink, as the aphid guide explains, and fine webbing means mites, which the spider mite guide covers.
One Last Tip
Put shiso on a separate timer from the start, even if it shares a shelf. It is tempting to plug everything into one timer at 14 hours and sort it out later, but shiso makes its flowering decision early, and a plant that has started flowering never quite goes back to making big leaves. A second plug-in timer costs less than a packet of seed, and it is the difference between a plant that crops for months and one that winds down after a few weeks.
Frequently Asked Questions
How long does hydroponic shiso take to grow?
Soaked seed sprouts in 4 to 7 days, or 7 to 21 days if sown dry. The first proper harvest comes 8 to 10 weeks from seed, and under strong light you can pick a few leaves from about 6 weeks. With regular pinching, a plant keeps producing for many weeks.
Why does shiso need 16 hours of light?
Shiso is a short-day plant, so it starts to flower when days get short enough, and 14 hours is short enough to trigger it. Under 16 hours on and 8 off it stays leafy and productive. Give it its own light and timer if the rest of your herbs run 14 hours.
Should I soak shiso seeds?
Yes. Soak them for 24 hours in room-temperature water before sowing. Soaked seed sprouts in 4 to 7 days, while dry seed takes 7 to 21 days and comes up patchily. Keep the seed moist and covered after sowing, because letting it dry out undoes the soak.
What pH and EC does shiso need?
Hold the pH at 5.8 to 6.2, aiming for 6.0. Feed seedlings at EC 0.8 to 1.0 and established plants at 1.0 to 2.0. Pale, slow growth means shiso is underfed, while large, soft leaves with weak aroma mean too much nitrogen.
Can shiso grow in a Kratky jar?
Yes, in a container of about 1 gallon; a quart jar is only marginal. Start with the net cup bottom in the solution and let the level fall so an air gap forms, since shiso hates waterlogged roots. For a full plant over months, a DWC setup of 2 to 3 gallons works better.
Is green or red shiso easier to grow?
Green shiso. Under identical conditions it has produced 58 to 270 percent more growth than red, and it responds well to feed strength. Red shiso needs brighter light to do well. Grow green for volume, and add red later if you want the color.
How do I harvest shiso so it keeps growing?
Once the plant reaches 6 inches, pinch stems just above a leaf node, pick outer leaves first, and never take more than a third at once. Harvest every few days to weekly, and pinch off flower spikes as soon as they appear so the plant keeps making leaves.
Why is my shiso flowering already?
Almost always because the days are too short. Shiso flowers when the light runs for 14 hours or less, which is why it needs 16 hours on and 8 off. Move it to its own 16 hour timer and pinch the flower spikes off, although a plant that has started flowering rarely returns to full leaf size.
How often should I change the water for shiso?
In DWC, top off daily with plain pH-adjusted water and change the reservoir every 2 weeks. In a Kratky container, do not top off daily: let the level fall, and if it runs low add a little nutrient solution, raising it by no more than about an inch.
What does shiso taste like?
Shiso has a complex aroma of mint, basil, anise and a hint of cumin. Green shiso is milder and is the one served with sushi, while red is slightly more astringent and is used to color pickles. Use it fresh in salads, over rice and noodles, or wrapped around fish.
