Once you begin sowing seeds indoors, it doesn’t take long to figure out there are advantages to starting some veggies earlier than what’s suggested on the seed packet. Tomatoes, for instance. Starting them ten, even twelve weeks early will give you larger plants and, in some cases, earlier fruit.
But there are a few vegetables you don’t want to get started early. Doing so could mean disaster when it’s time to plant them outside.
The Green Itch
Every January, I get the Green Itch. The holidays have wrapped up, the New Year celebration has come and gone, and there is still an infinity of dark, cold winter weeks to go. (At least, that’s how it feels.)
That’s when I pull out my seeds and start planning my garden. It doesn’t take long for planning to turn into planting. And before you know it, I’ve got all of my seedlings started.
Even the ones I shouldn’t be starting so early.
I noticed, when I did this, that I always had trouble with specific plants. Cucumbers, for instance. They would grow so quickly, and their leaves were so big that they would shade out the other seedlings—the same for my zucchini.
Not to mention, their little curly-q tendrils would start climbing up each other, the stems of other seedlings and the shelves of my little indoor greenhouse.
When it came time to plant them outside, it was always a headache trying to untangle them without snapping stems and breaking off leaves.
By the time they were transplanted into the garden, they were in rough shape.
But, for years, I kept at this because, in my mind, it made sense: sow seeds early – plant huge seedlings – get zucchini faster.
(I’m sure Mother Nature is shaking her head at me.)
The Trouble with Cucurbits
While this practice works wonders for things like tomatoes, peppers and eggplants (Do you notice a theme here? All members of the nightshade family.), it can be a disaster for cucurbits.
Here’s a quick refresher for seasoned gardeners and new gardeners alike.
Cucurbits, or Cucurbitaceae, are plants in the gourd family. Everything from the pumpkins you carve in October to the cucumbers you slice over a salad to the watermelon you enjoy at a summer picnic – are all cucurbits.
Here is a list of the most commonly grown cucurbits:
- Squash, winter and summer
- Pumpkins (also squash, but deserving of its own mention)
- Cucumbers
- Luffa
- Bottle and other decorative gourds
- Watermelon
- Muskmelon
Unlike other vegetables you may start indoors, cucurbits do not have a robust root system. They tend to have shallow root systems. What’s more, those roots do not like to be disturbed. Once they are in the ground, they would prefer it if you leave them be, thank you very much.
Moving them around too much can lead to leaf loss, extreme transplant shock or losing seedlings.
Cucurbits are natural climbers. As they creep and grow, spreading along the ground, they will put down roots at the joints (nodes) of their stems. These adventitious roots help hold onto the ground and add more sources of water and nutrients. But if those roots are disturbed, that section of the vine usually dies off.
This is why they have such shallow roots. They rely on many different contact points along the ground rather than a robust root system like tomatoes have.
If you start them indoors too early, they quickly outgrow their space and pots.
If it’s too soon to plant them outdoors, you’re stuck with one of two decisions. Pot them up and risk severe transplant shock, or let them continue to grow, becoming rootbound.
Rootbound cucurbit seedlings also tend to suffer from extreme transplant shock when they’re finally planted outside. Remember, they don’t like having those roots disturbed!
In either case, you’re left with a plant that can take much longer to bounce back and even longer for the roots to settle in and the plant to start growing again.
I’ve often had severely rootbound cucurbit seedlings die once I planted them in the ground.
These days, I’ve stopped sowing my cucurbit seeds early. I start the harder-to-germinate ones indoors a few weeks before my last frost date, and the others get direct sown. Here are some tips that can help you decide what’s best for your growing season.
Tips for Starting Cucurbits Indoors
- Don’t start them too early. It’s best to adhere to the time suggested on the seed packet.
- Start them in a pot that’s slightly larger than what you would use for other seedlings. The idea here is you want to use a pot that’s big enough to accommodate the plant until it’s ready to be planted outdoors. You don’t want to have to pot up with cucurbits.
- Give them plenty of space and ensure that other seedlings (including neighboring cucurbits) are not shaded out by their large leaves.
- Add a bit of mycorrhizae to the seed starting mix. This will encourage healthy root growth, which will lessen transplant shock when you move the plants outdoors.
Tips for Transplanting Cucurbits
- Always allow 4-7 days of hardening off outdoors before you transplant your cucurbits.
- Choose an overcast day—full sun and stress newly transplanted seedlings.
- Add a bit of mycorrhizae to the transplant hole. These beneficial fungi will create a larger root system, helping the plant to bounce back faster.
- Water in the plant immediately after planting. Don’t wait until you’ve finished all your cucurbits or each one of a specific variety. As soon as you’ve gently packed the dirt around the individual plant, follow up with water.
- Plant towards the end of the day, after the strong afternoon sun has passed where you are planting.
Don’t forget that because they are so fast-growing, many cucurbits can be direct sown once your weather allows for it. It might even be the best option, depending on your growing zone.
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