In my cool Pacific Northwest climate, plants that belong in the cucurbit (squash) family, including melons, cucumbers, summer squash like ‘Costata Romanesco’ and ‘Trombocino’ and winter squash, grow best when planted out as seedlings. Seedlings grow faster and produce fruit sooner than plants directly seeded into the garden with one caveat: you must plant small seedlings. If you buy seedlings, do not be tempted by plants that are beginning to vine. It turns out bigger is not always better. These larger plants tend to transplant poorly, grow slowly and underperform.
I have much better luck with very small seedlings. When cucurbit seedlings germinate the first “leaves” that appear are the spoon shaped cotyledons (also called seed leaves). The plants “true leaves” (the leaves that look like the plants regular leaves) emerge next. The best time to plant squash family seedlings is when the first true leaf is beginning to poke up between the cotyledons. This goes for store bought and homegrown seedlings.
Cucurbits really resent having their roots disturbed. Instead of separating seedlings growing in a clump, I ease the plants out of their pot and plant the whole group of seedlings in the ground (or container). I then give the plants a week or so to grow before I cut off the weakest plants at the soil line with scissors, leaving the strongest one to grow on. I like to pour about a cup of diluted liquid organic fertilizer around the newly transplanted seedlings, and I also set a cloche over the plants for a couple of weeks to keep them toasty warm.
I’m getting a bit of a late start on my summer garden, but I’m planning on getting some squash, tomatoes, peppers, and eggplants into the ground this weekend! I’ll let you know what I end up planting. So far I haven’t been able to find seed or seedlings of my favorite cucumber ‘Satsuki Midori’, so I might have to try something new!