How to Start Seeds for a Tower Garden
Learn how to choose crops, start seeds successfully and grow strong, healthy seedlings for your Tower Garden.
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Starting your own Tower Garden seeds isn't difficult, but those first few days after germination can make a big difference in the quality of the seedlings you eventually put into your tower.
You start your seeds, sit back with a cup of coffee and wait for the magic to happen. A week or two later, you've got seedlings — but instead of being short, stocky and healthy, they're pale, stretched and droopy. They look like they partied a little too hard.
So what happened? In many cases, the problem started right after the seeds sprouted.
How to Start Tower Garden Seeds: Quick Answer
- Start your seeds in rockwool cubes.
- Keep the rockwool moist, but don't leave it soaking wet.
- Plant the appropriate number of seeds for the crop you're growing.
- Provide strong light as soon as the seeds sprout.
- Allow seedlings to develop a few sets of true leaves before transplanting.
- When your Tower Garden contains all new seedlings, start with half-strength nutrients — 10 mL each of Mineral Blend A and B per gallon of water.
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Follow the process from rockwool to a healthy Tower Garden seedling.
The #1 Tower Garden Seedling Mistake
One of the most common mistakes we see Tower Garden growers make is not giving seedlings enough light immediately after they sprout.
When young seedlings don't receive enough light, they begin stretching toward the available light source. Instead of developing short, sturdy stems and compact growth, they become tall, thin and leggy.
What you're looking for are compact, healthy seedlings that are strong enough to make the move into your Tower Garden.
Step 1: Prepare the Rockwool Cubes
Tower Garden seeds are started in rockwool cubes rather than traditional potting soil.
Mix approximately one gallon of water with 10 mL each of Tower Garden Mineral Blend A and B. Soak the rockwool cubes in the solution for about 20 minutes, then remove them.
The cubes should be thoroughly moist, but you don't want them sitting saturated with excess water when you plant your seeds. Too much moisture can contribute to seed and root problems.
Important: Don't squeeze the rockwool cubes to remove water. Let excess moisture drain naturally so the structure of the rockwool remains intact.
Step 2: Plant Your Tower Garden Seeds
The number of seeds you should place in each rockwool cube depends on what you're growing. A tomato doesn't need the same number of seeds as lettuce or basil.
Rather than putting a handful of seeds into every cube, use the recommended amount for each crop.
Our Tower Garden Seeding Cheat Sheet shows how many seeds to place in each rockwool cube for common vegetables, greens and herbs.
Once planted, keep the rockwool moist while you wait for germination. Don't allow the cubes to completely dry out, but don't keep them waterlogged either.
Seeds Not Sprouting?
Germination time varies by crop. If you've waited longer than expected and nothing is happening, see Seeds Not Germinating? 5 Common Reasons Why .
Step 3: Give Seedlings Plenty of Light
This is the step you don't want to miss.
As soon as your seeds sprout, they need strong, consistent light. Waiting even a day or two can cause seedlings to begin stretching toward the available light.
☀️ Outdoor Seedlings
When conditions allow, give seedlings plenty of outdoor light. Our seedlings receive at least about 8 hours of sunlight when they're being grown outside.
💡 Indoor Seedlings
When starting indoors, use a grow light rather than relying on a bright room or window. Aim for approximately 14–16 hours of light each day.
📏 Keep Lights Close
Young seedlings need the light close enough to provide strong, useful illumination. When starting seedlings under tabletop grow lights, we generally keep the light about 4 inches above them.
Once a seedling becomes severely leggy, simply giving it more light doesn't make the stretched portion of the stem short and sturdy again. Prevention is much easier than trying to rescue a weak seedling later.
If you need an indoor seed-starting light, see our Tower Garden Germinator .
For more information about lighting throughout the growing cycle, visit our Tower Garden Light Guide .
When Are Tower Garden Seedlings Ready to Transplant?
Don't move a seedling into the Tower Garden simply because the seed has sprouted. Give it time to establish first.
Once your seedlings have developed a few sets of true leaves and the growth looks compact and healthy, they're ready to move into the Tower Garden.
A Healthy Seedling Should Be:
- Compact rather than tall and stretched
- Developing healthy true leaves
- Strong enough to remain upright
- Established in the rockwool cube
Moving weak, leggy seedlings into the Tower Garden doesn't fix the underlying problem. Starting with a strong seedling gives the plant a much better beginning.
Moving Seedlings Into the Tower Garden
Place the rockwool cube into the net pot or securely onto the appropriate Tower Garden growing clip and make sure the Tower Garden pump is running and water is circulating.
Start With the Right Nutrient Strength
When the Tower Garden contains all new seedlings, begin with half-strength nutrients — 10 mL each of Mineral Blend A and B per gallon of water.
Nutrient needs change as plants mature and can also change with temperature. If you're adding new seedlings to a Tower Garden that already contains mature plants, follow the appropriate nutrient recommendations for the existing tower.
See the Tower Garden Nutrient Guide for complete instructions.
Keep Providing Strong Light
Your seedlings still need plenty of light after they're moved into the Tower Garden.
- Indoors: Keep Tower Garden grow lights approximately 6–8 inches from the tops of the plants and provide about 14–16 hours of light per day.
- Outdoors: Gradually acclimate seedlings to full sun, especially if they were started indoors or in a protected location.
Watch for Early Problems
If healthy seedlings suddenly begin struggling after they're moved into the Tower Garden, start by checking the basics:
- Is the plant receiving enough light?
- Are you using an appropriate water source?
- Is the nutrient strength correct?
- Is water circulating properly through the Tower Garden?
Common Tower Garden Seedling FAQs
Can I Start Tower Garden Seedlings in Front of a Window?
A sunny window may look bright to us, but it often doesn't provide young seedlings with enough consistent light to produce the short, sturdy growth we're looking for.
If your seedlings begin leaning or stretching toward the window, that's a good sign they need stronger light. Move them outdoors when conditions are appropriate or use a grow light indoors.
What If It's Too Cold to Put My Seedlings Outside?
If daytime temperatures are above about 50°F, seedlings can spend time outside, but bring them back inside when temperatures become too cold. A seedling heat mat can also help keep rockwool warmer during cold conditions.
Cool-weather crops such as lettuce, leafy greens, kale and broccoli are generally better choices during cooler growing conditions than warm-season fruiting crops.
Why Did My Seedlings Wilt After I Put Them in the Tower Garden?
If seedlings looked healthy before transplanting but decline after going into the Tower Garden, check your water source, nutrient strength and growing conditions.
City water containing chlorine or chloramine can cause problems for plants. Our Tower Garden Water Guide explains which water sources work best and when filtration may be needed.
Do I Need to Keep Watering Seedlings With Tower Garden Nutrients?
No. After the initial rockwool soak, use plain water while the seeds germinate and begin their early growth. The seed contains what it needs during this first stage.
I Planted Too Many Seeds. Should I Thin Them?
It depends on the crop. Herbs and some lettuces can grow with multiple plants in one cube, while larger fruiting crops need much more space. You definitely don't want ten tomato plants competing in one rockwool cube.
Use our Tower Garden Seeding Cheat Sheet to see how many seeds to use for different crops.
The Secret to Strong Tower Garden Seedlings
Starting Tower Garden seeds successfully really comes down to three things: consistent moisture, the right number of seeds and plenty of light as soon as they germinate.
Get those first few weeks right and you'll have short, healthy seedlings ready to make the move into your Tower Garden.
