My lettuce looked like something had taken a tiny blowtorch to the leaf edges. Brown, crispy tips on otherwise healthy-looking plants, maybe three weeks into a grow. I’d been so careful with my nutrients, checking the reservoir every few days, and I was convinced I’d overdone something. Turns out I hadn’t poisoned my lettuce at all. I’d been causing tip burn through a combination of light being too close and zero airflow over the canopy. Took me two more failed grows to actually understand what was happening.
- Tip burn is a calcium delivery problem, not nutrient burn. The plant can’t move calcium fast enough to leaf tips.
- The five main causes are: light too close, EC too high, low airflow, warm water temps, and a variety that’s naturally more susceptible.
- A small clip fan ($10-12) pointed across the canopy is often the single fastest fix.
- Buttercrunch, Oakleaf, and Little Gem are the most tip-burn-resistant varieties for AeroGarden grows.
What Tip Burn Actually Is
Here’s the thing that surprised me when I looked it up: tip burn isn’t caused by too much of the wrong nutrient. It’s a calcium deficiency, but not because there’s no calcium in the water. It’s because calcium only moves through a plant via transpiration. The leaves pull water up from the roots, and calcium rides along with it. When that process slows down or the innermost, fastest-growing leaves can’t transpire fast enough, those cells don’t get calcium in time and they die. That’s the brown edge you’re seeing.
So adding more nutrients won’t fix it. In fact, higher nutrient concentration often makes it worse.
The Five Root Causes (and How to Fix Each One)
Light too close. AeroGarden’s default light schedules and heights are designed for herbs, which are tougher than lettuce. Lettuce is a low-light crop and it grows fast. When the light arm is too low, the canopy heats up, transpiration goes haywire in the outer leaves while the inner growth stays stressed, and tip burn follows. I keep my light arm at the maximum height for lettuce and run 14 hours on, not the 16 that the app sometimes suggests. The AeroGarden Bounty Basic buy on Amazon has more height adjustment range than the smaller units, which genuinely matters for full-size lettuce heads.
EC too high. Higher salt concentration in the reservoir makes it harder for the plant to absorb water. That slows calcium transport directly. For lettuce, I target an EC of 0.8 to 1.2 mS/cm. If you’re using the AeroGarden liquid nutrients at the recommended dose and seeing tip burn, try dropping to half or even a third of the suggested amount. Lettuce doesn’t need as much as herbs.
Low airflow. This is the one most people skip. Airflow across the canopy is what drives transpiration in the inner leaves, and without it, those fast-growing young leaves simply can’t move calcium. A small clip fan running at low speed, aimed to blow across (not down into) the plant tops, made a visible difference in my grows within about a week. I use a cheap USB clip fan from Amazon for around $12. Not glamorous, but it works.
Water temperature too warm. Warm water holds less dissolved oxygen and slows root function, which limits how well the plant can uptake anything, calcium included. Aim to keep your reservoir below 72°F (22°C). In summer, this is harder than it sounds. I’ve wrapped my reservoir in a towel-and-frozen-bottle setup during heatwaves. Inelegant, but it works. If you’re consistently running warm, that’s a reason to grow lettuce in fall and winter instead.
Wrong variety. Some lettuce types are just more susceptible. Looseleaf varieties like Oakleaf handle confined spaces better. Buttercrunch and Little Gem are frequently recommended across r/aerogarden as tip-burn-resistant picks. Romaine and crisphead types (think iceberg-adjacent) show tip burn the most. If you keep having problems, switching variety alone can make a big difference without changing anything else.
Nutrients and Calcium: What to Look For
The stock AeroGarden liquid nutrients contain calcium, but once you’ve run a few reservoirs and the ratio of calcium to other minerals shifts, or if you’re running a higher concentration chasing faster growth, things can get unbalanced. If you’re looking at third-party options, the Hydroponics Nutrients for AeroGarden A&B solution (800ml total) buy on Amazon and the Ambgrow 800ml A&B Hydroponic Nutrients buy on Amazon are both compatible with AeroGarden systems. When comparing any A&B formula, look for one that explicitly lists calcium in its formulation. If it’s not mentioned anywhere on the label or product page, choose something else.
Also: don’t skip the “B” bottle and just use “A.” The two-part system exists because calcium and some other minerals precipitate out of solution if stored together. You need both, added separately to the water.
Troubleshooting Quick Reference
| Symptom | Likely Cause | First Fix |
|---|---|---|
| Tips burn on outer leaves, inner leaves fine | Light too close, heat stress | Raise light arm to max |
| Tips burn on inner/young leaves first | Low airflow, fast inner growth | Add clip fan across canopy |
| Widespread tip burn across the whole plant | EC too high | Cut nutrient dose by half |
| Tip burn gets worse in summer | Warm reservoir | Keep water below 72°F |
| Persistent tip burn despite fixes | Susceptible variety | Switch to Buttercrunch or Oakleaf |
What to Expect in the First Two Weeks
Once you’ve made a fix, the existing burned tips won’t recover. Those cells are gone. What you’re watching for is whether new growth comes in clean. Give it 10-14 days before deciding if a change worked, because the leaves that were already forming when you intervened may still show damage. If new leaves emerging after your fix look healthy and the burning has stopped progressing, you’ve solved it.
If you’re still seeing fresh tip burn after two weeks and you’ve addressed light height, airflow, and EC, check your water temp and then seriously consider swapping variety on your next grow.
The AeroGarden Harvest buy on Amazon is a solid entry point if you’re just starting out, though the smaller footprint means less room to manage airflow around a full lettuce canopy. It holds up to 6 pods and works fine for cut-and-come-again looseleaf, which is also more forgiving of tip burn than heading varieties anyway.
Frequently Asked Questions
What causes tip burn in AeroGarden lettuce? Tip burn is a localized calcium deficiency caused by the plant’s inability to deliver calcium fast enough to the fastest-growing leaf tissue. It’s a transpiration problem, not a sign of bad nutrients. Poor airflow, light that’s too close, and high EC all contribute to it.
Can I fix tip burn after it starts? The browned tissue is dead and won’t come back. But you can stop new damage from appearing by fixing the underlying cause. Check your light height, add airflow with a small fan, and reduce your nutrient concentration. New growth should come in clean within 1-2 weeks if you’ve addressed the root issue.
Which lettuce varieties are best for AeroGarden to avoid tip burn? Buttercrunch, Oakleaf, and Little Gem are the most reliable picks for tip-burn resistance in countertop hydro setups. Romaine can work but needs more careful airflow management. Crisphead types are the most prone and the hardest to manage.
Does water temperature affect lettuce tip burn? Yes, directly. Warm water reduces dissolved oxygen and slows root function, which limits how well the plant can take up water and the calcium dissolved in it. Keep your reservoir below 72°F if you can, especially during summer grows.
How often should I change the water in my AeroGarden when growing lettuce? Top off with plain water as needed between changes, and do a full reservoir swap every 2-4 weeks. When you change the water, clean the reservoir walls while you’re in there. Algae buildup and mineral deposits can interfere with root health, which eventually shows up as nutrient uptake problems.
The fan is genuinely the fix most people resist because it seems too simple. I put it off for two full grows before caving, and my tip burn dropped dramatically after the first week with it running. Start there, adjust your light height, back off on nutrients, and then worry about water temp and variety if you’re still fighting it. Most people solve it with the first two.
If you’re setting up a new system and want the easiest path to managing all of this, the Bounty Basic gives you more light arm clearance and room to work with. Drop a comment below if you’re still seeing burns after running through these fixes. Include your variety and reservoir temp and I’ll take a look.