Previously we discussed seeding and indoor growing to get a head start on the season. Next, we will identify when your plant starts are ready to go outside.
Growing in Cells
I personally like seeding into a 72-cell tray. Each cell is about 1.5”x1.5” which works well enough for most young plants. Brassicas, like broccoli and brussel sprouts fill the cells pretty well with their roots that they should pull out pretty easily when they are ready to plant. Alternately, if left too long, the roots will take over and the plug could become root bound and stunt growth when planted.
Other seeds like tomatoes will need to be repotted a couple times before they are big enough to plant in the ground, or container.
Root vegetables are usually not well suited to transplanting from cells. Radishes, turnips, carrots, parsnips and beets are best sown directly into the ground. Carrots and parsnips, with their long, thin taproots especially, can quickly get stunted by the restrictive size of the cells.
Frost Dates
When looking at what plants you want to start from seed, knowing your local last frost date is important. The frost date is based on historical weather trends and tells you when the chances for frost after that date drops to 30%. We all know Wisconsin weather, and since there’s always a chance of winter until June, you might want to wait another week past the frost date if you’re really worried about cold damage.
The frost date can also vary dramatically over a geographically small area. For example, the last frost date for Sheboygan is April 28th, while it’s May 14th in Sheboygan Falls.
Once you’ve figured out the final frost in your area, you can start planning where and when to start your seeds. Vegetables like beets can be seeded into the ground up to a month before the last start date, while more cold sensitive vegetables like tomatoes should be started inside 6-8 weeks before the final frost. Here is a list of commonly grown vegetables and when and where they should be planted based on the frost date. If you’re growing something not on the list, it will most likely say, on the back of the seed packet, when to plant relative to the last frost date.
Repotting
A lot of seedlings won’t need to be repotted, but if you have the time and desire, stepping up the size of the pot a seedling is in can give it a good head start when you’re ready to finally plant. Tomatoes are a good example of a plant that benefits greatly from repotting. If you can get the plant to around 1’ tall by the time it’s ready to plant outside, you’ll have a much longer and productive growing season from that plant. Repotting is also helpful if you just need to delay planting outdoors for a little longer and need to keep the plant from becoming root bound.
Brassicas don’t need repotting. If they are around 3”-5” in the cells, they should take off nicely when planted into good soil.
Like tomatoes – squash, pumpkins, cucumbers, and zucchini will all benefit from repotting until they are somewhere around the size of the tomatoes in pots 2 and 3.
Hardening Off
If you started seeds indoors, it’s best to “harden off” the seedlings gradually so they are not shocked by the volatility of outdoor weather conditions.
After outdoor temperatures are consistently above 45 degrees Fahrenheit, you can start hardening off plants.
-Two weeks before you want to plant them, take the starts outside.
Keep them out of direct sunlight and wind for one hour.
Every day increase exposure by an hour, while being mindful if the temperature dips too low, or it’s too windy outside.
Gradually increase sun exposure as well, moving from shade, to partial shade, to full sun just before planting.
If overnight temperatures are reliable over 50 degrees, you can leave them overnight towards the end of hardening off.
If you are growing seedlings inside, you can use a gentle fan or breezy window to help your seedlings toughen up their stems before taking them outside.
So, are you ready to plant your seedlings?
Check these conditions first:
The roots are sufficiently developed
You’re on the right side of the last frost date in your area
You’ve repotted your plant to the appropriate size
You’ve gradually acclimated the seedlings to outside conditions
Next up, Planting! Stay tuned for our next post!