Multi-sowing is just as it sounds, sowing more than one seed per cell or planting module.
Now, I have done this for quite a while but for different purposes. I generally sow extra seeds in cells to make sure I have enough seedlings should a seed not germinate.
Then, when seedlings get their first set of true leaves, if not slightly earlier, I'll prick out the extra seedlings and transplant them to their own private cell. I hate thinning (i.e. killing) seedlings and this practice has saved me from doing that most times.
However, with multi-sowing, you purposely leave a certain amount of plants to grow in the cell together AND then you plant them into the ground together.
Why would you do this?
Several reasons, in fact:
- To grow more plants in one space (whether that's in a seed cell or out in the garden)
- To get a higher yield of a plant in a small area (this is especially helpful if you have limited growing space)
- To use less seed starting mix, potting soil, compost & other seed-starting resources (in other words, fewer resources used = less money spent)
- To save time growing two or more seedlings at once (you'll also save time fishing out the extra seeds your drop OR thinning them later)
- The Companion Effect: Charles Dowding has observed in his 40 years of gardening that some plants enjoy having companions to share their space. Who knew?
When space is at a premium in your seed starting or propagation space, it makes sense to grow more plants in the same area.
While not all plants can benefit or handle sharing their space with close companions (for example, larger plants like tomatoes, peppers, and eggplant), other plants quite enjoy have a companion.
Additionally, some plants not listed below do fine multisown with their comrades. The question is, however, how do you plan to use them?
For example, if you're growing cabbages and lettuces for the entire plant (versus just the outer leaves), you will want to sow them singly so they will produce a nice, big heart.
However, if you are growing lettuces for their outer leaves, you could feasibly grow two or three plants together to achieve that goal.
Likewise, mustard and arugula do well planted in clumps of two or three and their outer leaves are relatively easy to harvest in that fashion.
While radishes, beets, and turnips all grow well in clumps, rutabaga and celeriac will not produce as large of a root as you may desire.
Similarly, carrots and parsnips will likely develop "forked roots" if sown in clumps, which is why it is best to directly sow them into the ground in rows and then thin down to one plant per space.
There are limits, however, to how many seeds you will want to plant in one cell.
If you overcrowd root crops, like beets and radishes too much, you will most certainly grow smaller roots, though their leaves will be abundant for harvesting. On that note, beet and radish leaves are completely edible and great to add to salads, stir fries and more.
So then you may be wondering how many seeds per cell should you sow? Well, let's get into it, shall we?
The 5 Best Plant Groups & Seed Numbers
Below are the "plant groups" that I find work best sown in multiples, as well as how many seeds you'll generally want to place in each cell. NOTE that the "SEED" amount differs from the "PLANT" amount and that is to account for germination.
If one or two seeds don't germinate, then you're set. But if all the seeds germinate, thin out a few seedlings to keep the number of plants in each cell manageable.
Also NOTE differences within the Leafy Greens category. "Salad" greens refer to harvesting smaller leaves for "baby greens", typically used in salads; while the larger leaves are usually used for cooking. You will want to account for this when deciding how to grow these specific plants.
As with anything in gardening, some of this comes down to preference. You will decide over time what works for you and what doesn't. But in general, this reference chart is a great place to start practicing multi-sowing seeds.