Have you ever pulled off the cover of your microgreens tray and thought, "Why are they only growing on one side?!" Uneven growth - where part of the tray is thriving and another part is sparse, shorter, or struggling - is a common puzzle. It can show up as patchy germination, one end of the tray looking great while the opposite end looks stunted, or even a ring of shorter plants surrounded by taller ones. Don't worry, you haven't angered the microgreen gods; there are logical reasons for this. In this guide, we'll break down why microgreens might grow unevenly and how to fix and prevent it. By tweaking a few aspects of your setup, you can achieve that holy grail: a tray of microgreens that's uniformly lush from corner to corner.
Diagnosing the Uneven Growth
First, let's identify the pattern of unevenness - this gives clues to the cause:
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One Side or One Corner is Shorter: Perhaps the side of the tray closer to the window is taller (or vice versa). This often points to differences in light exposure or possibly how water distributed (like if a tray is slightly tilted).
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Center of Tray is Sparse or Stunted, Edges OK: Sometimes the middle of the tray doesn't grow as well as the outer edges. This can be caused by either water not reaching the center (if you misted only the edges, or bottom-watered and the center stayed dry), or the opposite - water pooling in the center making it too wet (if the tray sags in the middle). Also, if weight or pressure during germination wasn't even, center seeds might germinate differently.
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Random Patches Bare: That could be uneven seeding (some spots just didn't get seeds or they were pushed aside) or maybe some seeds were clumped and rotted.
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One Half Clumpy, Other Half Fine: Possibly when sowing, more seeds ended up on one half than the other, or maybe one half of the tray got different treatment (like if you had two types of seeds or a slight delay in sowing one side).
By identifying where the problem is, we can match it to causes:
Common Causes of Uneven Growth
1. Uneven Light Distribution: This is a top cause. If your light source is stronger on one side, microgreens on that side will grow faster and taller. For example, a tray placed near a window will receive more light on the window-facing side. The far side might be in shadow and grow slower or stretch toward the light, remaining smaller. Similarly, under a grow light, if the bulb or LED strip isn't perfectly over the center, edges might get less light. Even a slight tilt of the light or a reflector issue can create a light gradient across the tray. The result: a lopsided tray where one side is flourishing and the other is lagging.
2. Uneven Watering or Moisture: Water is life, and if it's not evenly available, growth won't be even. This can happen in a few ways:
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Dry Spots: Perhaps when you misted or watered, some areas didn't get adequately wet. Seeds in a dry pocket won't germinate at the same time (or at all). Or if you bottom-watered and your tray or surface wasn't level, one end might have sat in water while the other end remained a bit dry. The drier side will germinate slower and grow shorter due to moisture stress.
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Overly Wet Spots: Conversely, if water pooled in one area (often the center or a lower corner if tray is tilted), seeds might have rotted there or seedlings got waterlogged. For example, one grower found their tray was slightly dipped in the middle, causing water to collect and those middle plants grew slower due to less oxygen at roots. Edges, which drained better, grew taller.
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Watering Technique: If you always water from one side of the tray, the nearest side might be getting soaked while far side gets less. Over time, that could lead to differences.
3. Uneven Seeding (Distribution & Density): It's surprisingly easy to accidentally sow more seeds on one half of the tray than the other. If one side of your tray has double the seed density, initially it might germinate thickly, but seedlings could compete and some may die off, leading to patchiness. The densely sown side might also hold more moisture (from all those seed hulls and gel, if mucilaginous seeds, etc.), which could foster mold or slower growth there. Meanwhile, the sparsely seeded side has fewer plants - each can get more light and space, possibly growing taller. Ideally, you want to sow evenly so all areas have similar seed counts. Clumping of seeds (e.g., if you accidentally poured a bunch in one spot) will definitely cause an uneven outcome.
Also, consider if you used a shaker or your hand - sometimes the first area you sow gets more seeds and as you move, you run out, resulting in a gradient. Practice and intentional division of seeds (like sow half over the tray, then the other half, as some suggest) can ensure more uniform coverage.
4. Germination Variability: Not all seeds sprout at the exact same hour. Some variability is natural. But if a portion of seeds took much longer (or didn't germinate well), that area will be behind. Causes for slower germination in one area include:
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That area got colder (maybe it's by a cold window or draft).
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Seeds might be from a different batch? (If you accidentally mixed or if the distribution ended up segregating some older seeds).
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Depth differences: Microgreen seeds generally sit on the surface or lightly covered. If during sowing or covering, some seeds got pushed deeper (e.g., by uneven weight or maybe you accidentally piled more soil in one part), those buried seeds may struggle or sprout later.
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Weight distribution: If you stack trays or place a weight on top for germination, ensure it's even. A common tip is to use another tray as a lid and even place a small weight on it to press seeds into soil. If that weight was, say, a brick placed on one side, that side's seeds had more pressure (which might aid contact, actually leading to better germination there but could also compact soil too much). Meanwhile the un-weighted side might have looser contact and worse germination. One Reddit user found that uneven weight led to the middle of the tray (where weight was heaviest) germinating great, but edges where contact was looser were patchy.
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If you use a spray bottle, sometimes the force can push seeds to the edges or cluster them, causing the center to have fewer seeds (hence uneven stands). Some growers cover seeds with a thin layer of soil or vermiculite to avoid dislodging when watering.
5. Tray or Surface Levelness: We touched on it, but to emphasize - if your tray isn't sitting flat, water will flow to the lowest point. That low point often becomes waterlogged (slow growth, possible mold), and the high point becomes relatively drier (slower germination or growth due to thirst). Always place trays on a level surface. If your table is uneven, consider shimming it or rotating tray orientation each day. Some people even use gardening trays with capillary mats to ensure even moisture, but that's not required if you manage watering well.
6. Mixed Varieties in One Tray: Did you perhaps sow two different kinds of seeds in sections of one tray? If so, uneven growth is expected because different microgreens grow at different rates. For instance, radishes shoot up in 5 days, but if you also sowed celery in part of the tray, those are much slower. Generally, it's recommended to only mix seeds with similar growth times or manage them separately. So if one half is a different variety, that explains it - and the solution is simply to harvest each part at its appropriate time or avoid such mixes.
7. Microclimate Differences: Look at the environment: is one side of the tray near an AC vent blowing cold or hot air? Is one end of the tray closer to a heat source? Even differences like one side being by a wall (warmer, less airflow) and the other side open can subtly affect growth. It's usually minor, but in some setups it might contribute.
Now, let's move to solutions.
How to Fix and Prevent Uneven Growth
1. Rotate and Reposition: A simple habit is to rotate your trays 180° each day under the light or in the window. This evens out any light disparities. If one side was getting better light, rotating means the other side gets its turn. Many growers do this routinely - it's like turning a houseplant so it grows straight. If using sunlight, you might rotate more frequently (morning vs afternoon positions). This will help plants on the formerly shaded side catch up. Over a few days, you may notice the once-short side growing more to even out. Keep in mind, rotation won't resurrect seeds that never germinated, but it will balance growth of those that did.
2. Water Evenly: When bottom watering, ensure the tray sits flat in the water. After a few minutes, check if all areas of the soil are moist. If you discover one corner tends to stay dry, try adding a little extra water and tilting the tray gently to that corner to distribute water. Or simply pour a bit of water directly on that spot. For top watering, use a fine mister or watering can that can cover the whole tray area uniformly. Start watering outside the tray and sweep across, so the edges get as much as the center. Watch out for water running off one side. Also, after watering, you might lift the tray and tilt it slightly in each direction - if water drips out a corner, that corner had excess (showing tilt or overwatering there). Dump any pooled water. The Reddit example we saw had the grower checking moisture with a finger in the center of the tray, which is smart. Do that: gently poke a finger down to feel if the middle is as moist as edges.
If you suspect under-watering caused a patch, you can try to carefully water that area and see if late seeds sprout. Sometimes seeds are resilient and will come up once given moisture, albeit delayed. But often, prevention in the next batch is the key.
3. Level the Playing Field: Make sure your tray and growth medium are level. Before sowing, level out your soil or medium in the tray, patting it flat but not compacted. A flat surface ensures seeds contact evenly and water spreads uniformly. Use a level (or the water test: pour a bit of water and see if it pools in a certain area). If one side is low, prop it up or add a bit more soil there. Also check your shelf or sill - use a bubble level or even a phone app to see if it's reasonably flat. It doesn't need to be perfect, but the closer to level, the better the uniformity.
If using multiple trays stacked in germination, ensure even weight. Instead of placing one heavy object on one side, use lighter, more evenly spread weights if needed. Or if stacking trays, rotate which way they're oriented so any slight warps average out.
4. Sow Seeds Uniformly: Take your time during seeding. One technique is to split your measured seed into two cups; sprinkle the first half over the whole tray, then the second half, perhaps in a perpendicular pattern. This way if your first pass was uneven, the second pass helps fill gaps. You can also physically divide the tray in your mind into quadrants and ensure roughly equal seed goes into each quadrant. Tools like a shaker bottle can help disperse seeds more evenly instead of dumping. If dealing with small seeds that clump (like basil, chia), mix them with dry sand or use a shaker with holes - it helps avoid dumping a blob in one spot.
After sowing, inspect - if you see a visible bare area with few seeds, manually sprinkle a pinch more there. Try to avoid huge clumps; you can use a toothpick or finger to redistribute seeds gently if you see piling. An even spread at the start leads to an even carpet at the end.
5. Ensure Consistent Germination Conditions: Keep the whole tray covered equally during germination. If using a blackout lid, cover the entire tray. If one part was exposed to light early and others not, that could cause differences. Similarly, keep moisture consistent - mist across the tray before covering, not just one side. If using a weighted cover, use something that gives even pressure (like another tray or a board that covers the whole tray). People have gotten creative: some use a sheet of cardboard cut to tray size under the weight to distribute it. As soon as seeds germinate, uncover fully so all sprouts get light at the same time.
6. Address Micro-Environments: If you suspect a draft or heat source on one side, adjust your setup. For instance, don't place half the tray over a heating mat and the other half off it. Or if one side faces a cold window, maybe put some insulation between the tray and window or just rotate more often. Aim for uniform temperature around the tray (most times this isn't huge, but in some cases it can matter).
7. Different Varieties - Best to Separate: If your uneven growth is because you mixed varieties with different speeds, the solution is to sow them in separate trays or sections that you plan to harvest at different times. For example, don't mix radish (fast) with parsley (slow) in one tray expecting uniformity. If you want a mix, combine seeds that germinate and grow within a day of each other. Otherwise, accept the unevenness or harvest in parts (nothing wrong with harvesting one side earlier than the other if needed). But it's easier to grow each type to its perfection then mix post-harvest if you desire a mix.
8. Harvest Smart: If despite best efforts you still get a bit of unevenness, you can manage it. Harvest the ready parts and give the slower areas a tad more time. In one Reddit case, a grower did exactly that: cut the tall edges of pea shoots that were ready, then watered a bit more and let the center grow longer. It worked - after removing competition and giving attention to the stunted area, those caught up and were harvestable a bit later. Microgreens are quite forgiving; as long as there's no disease, you can often nurture a slower section to finish.
Conclusion: From Patchy to Picture-Perfect
Uneven growth can be frustrating when you want that Instagram-worthy even canopy. But once you identify the cause - be it light, water, or seed distribution - it's usually straightforward to correct. The key is uniformity in what you provide: uniform light, uniform moisture, uniform seeding. The plants will do their thing once conditions are consistent.
Don't be afraid to make small adjustments mid-grow: rotate trays, re-moisten a dry patch, maybe trim an overcrowded clump. Each batch teaches you something. Keep notes if you like (e.g., "south side of shelf gets less light - rotate!" or "add extra mist in center at sowing"). Soon enough, you'll be routinely churning out even, beautiful microgreen trays.
At Deliseeds, we test our seeds for reliable, even germination - a crucial factor in uniform growth. Starting with vigorous seeds means each one sprouts around the same time, giving you that nice even start. Combine that with the techniques above, and your next microgreens tray will be evenly lush. No more half-empty trays or lopsided growth - just a satisfying, uniform "micro-green carpet" ready to harvest. Happy growing, and may all your future trays be full and even!