It has been absolutely beautiful out for the past several days- the average high temperature has been around 68F, and the overnight lows have only dipped into the high 40’s once! My crocuses started blooming during the first week of the month, the first of my daffodils popped open on Friday, and my lilacs are swelled up with new buds. These, to me, are the first real signs of spring, and I wait for them expectantly every year. An inexperienced gardener might think that with all of this activity, it’s now safe to just get those plants outside and into the ground. The more experienced gardener knows better, though, and this week’s weather forecast is a perfect example of why. For my area, temperatures are expected to drop into the 20’s for the next few nights, and there’s potential for snow tonight!
I am in Zone 6B. You can find what zone you are in by going to the following site and entering in your zip code: USDA Hardiness Map
The reason you need to know your zone is because it gives you important information on your first and last frost dates, and when you need to be prepared for the dreaded ‘hard freeze’. Seedlings are delicate things, and few will survive extreme temperatures without some help.
Knowing that I am in Zone 6B tells me that my last frost date is between March 30 and April 30, in the fall, my first frost date is between September 30 and October 30, and the coldest it’s likely to get in the winter is -5 to 0 F. (The cold temperature is useful knowledge if you’re looking to plant trees or other perennials.) Plugging my zip code into the PlantMaps site narrows it down further for me- my average last frost is April 21-31, and average first frost is October 11-20. That means that I should not be surprised by the cold snap we are entering into right now, and I should be prepared for more cool weather at least through the first week or 2 of May.
So what can you do to protect those fragile seedlings out in the garden? You have a few options, and all of them involve covering them to give them protection against the chill. The seedlings and the earth put off a bit of heat, and the idea is to trap some of that heat in the seedling’s environment.
You can go buy row covers for them- an easy, though potentially expensive option.
You can buy cloches for them, but that can be very expensive if you have a large garden.
You can mulch them up with old leaves, grass clippings, straw, or hay- if you have access to this stuff at this point in the year.
You can cut the bottoms off of clear or translucent plastic milk, soda, juice and water bottles to create little greenhouses for each of the seedlings. This would be a bit time consuming and not practical for things that get planted super close together like beans and peas, but uses something that would be destined for the recycle bin, and they can be nested together and stacked in the garden shed (or where ever you keep your supplies) for repeated use.
You can make your own row covers- it requires a little work, but these can also be used to extend your growing season if you want. Most of the DIY instructions I’ve seen involve making a frame out of PVC pipe or somesuch, and then covering it with special row cover fabric, but you could achieve the same results by lashing branches together and using plastic sheeting or tarp, which would bring the cost down substantially. How-to info is all over the web. I found pages with good info here and here and youtube videos here and here.
The nice thing about the floating row covers is that they can be used as a greenhouse, too. That means you’ll have more space for starting seeds, can get the seeds started earlier, and can extend your growing season beyond the standard frost date recommendations.
So there you have it. Why you need to know your hardiness zone and frost date info, and some options to protect those tender young seedlings. If you have any tips, I’d love to hear them!