Your seedlings have served their time and it’s time to start your own seeds but you may be wondering “how many seeds should I use?” Don’t worry, I’ve got you covered!  When seeding in rockwool for the Tower Garden it is important to have a good quality seed.  As we often use just one seed per rockwool cube we immediately notice if they fail to germinate (unlike traditional gardening where we sprinkle a whole row of seeds and thin them out later)



When seeding most lettuces you will use just one seed.  Yep, hard to believe that teeny tiny seed will produce that big luscious head of lettuce.  There are a few exceptions to this rule.

Head Lettuce
1 seed – Lettuces like Bibb and even Iceberg (did I just say that out loud) need just one seed. Using multiple seeds is not a good idea as you will have multiple heads trying to grow out of one tiny piece of rockwool.

Leaf Lettuce
1 seed – For red leaf, green leaf, romaine etc use just one.  HOWEVER, during the summer months I recommend using 2-3 seeds.  Why?  Lettuce is a cooler weather crop and has a tendency to bolt in the heat.  If you use 2 or 3 seeds you will have more lettuce growing, even though you harvest it a little sooner.  WINNER!

Spring/Mesclun Mix
6-8 seeds is the norm for mixed lettuce.  Personally, I like to use a few more (up to 12 seeds) as I prefer to harvest my lettuce as baby lettuce.


20+ seeds.  The more seeds, the bigger the bunch but do not use more than 50 seeds!

All Other Herbs
6-8 seeds for every other common herb I can think of.


Leafy Greens
1 seed – Kale (all varieties), Chard, Collards, Mustard Greens etc.  You can use 2 if you like but bear in mind that the stalk on chard gets HUGE and you will have more produce with two plants but you will have to replace it sooner as it simply out grows the hole.  WATCH OUT WITH CHARD.  It will break the shower cap if you leave it in too long.  I’m talking from experience here. 😉

2-3 seeds – Spinach etc

6-8 seeds – Arugula

Fruiting Vegetables 

1-2 seeds – Beans, Peas, Cucumbers, melons (all varieties).  You can use up to 2 seeds for these crops.  They do not get large stems, large leaves and single bean and pea plants do not produce a great deal so having two plants growing from one rockwool cube can be beneficial.  Just be careful when pruning and training the bean plant.  You do not want to over prune and remove too many leaves from one of the plants.  It can be difficult to distinguish between the two separate plants.

1 seed – Squash, Tomato, Pepper, Eggplant, Okra etc.  Just one seed is enough for these guys for a number of reasons.  Many have large leaves and/or grow like weeds.  More is certainly not better when it comes to the number of seeds per rockwool cube for these crops.  You will have so much foliage the air flow is reduced and fungus’ can become a bigger problem.


We do not recommend starting strawberries from seeds.  They do not produce well until their second year and they grow extremely slowly.  All they do is take up valuable real estate space in your Tower Garden.

As we often use just one seed per rockwool cube it is important to use a good quality seed.  When using just one seed per cube we immediately notice if they fail to germinate (unlike traditional gardening where we sprinkle a whole row of seeds and thin them out later).  Not sure where to get good quality seeds?  Check out this post to learn about some of my favorite companies.

Having trouble getting your seeds to germinate?  This post may provide some answers! “Why didn’t my seeds Germinate?”

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