Most plants can handle a good amount of stress until they give up the ghost, but they’ll never flourish to their full potential if they are stressed. Annuals, in particular, will seem to freeze in the state in which you buy them (or even decline) during periods of stress.
There are things you can do to help your plants through that transition, decreasing their stress and making sure that they get on with the growing as soon as possible.
If you are shopping for perennials and they were already outside at the nursery, you don’t have to do anything special for them. You can plant them as soon as you get home, but the best days for planting are overcast (and if there is some rain in the forecast for later that’s even better). A hot, sunny day is not the best for planting.
Annuals are almost always grown in greenhouses so they will be very unhappy if they are immediately thrown in the garden to fend for themselves. They need a few days to acclimate to being out of the cozy greenhouse before they are thrown in the garden or a pot to essentially fend for themselves. This is called “hardening off” plants and it is the single best thing you can do to ensure that you get the most out of your precious plants.
There are a few ways to harden off plants and a lot depends on the weather when you’re doing it. If cold is a problem (and I would say it is if nights are dipping into the low 50s or below), you’re probably going to want to move them into a garage at night and then pull them back out during the day. In a pinch you can also cover them at night with an old quilt or maybe several layers of burlap, but you’ll want to construct some kind of makeshift framework so the covering isn’t laying directly on your plants and crushing them.
During the day, the last place you want your new plants is in the blazing sun, even if they are plants that thrive in full sun. It’s quite bright outside, even in the shade, so start them in a shady spot. You can gradually move them into the sun. If you have no choice but to leave them in a spot that is shady part of the day and sunny at others, you can buy some shade cloth or row cover at any garden store or most hardware stores. This is white plasticy “fabric” that comes on a roll that has little perforations in it. You can cut a piece and just drape it over your plants (make sure it doesn’t blow away). It is light enough that it won’t damage them unless it rains on top of it.
Speaking of rain, it goes without saying that it’s really important to keep your plants watered during the hardening off period. That doesn’t mean soaking wet … just damp. Don’t let them dry out in between waterings, especially if you have a flat of small plants. Those can be nearly impossible to rehydrate.
Because I have so many plants (I buy annuals as I see them once I know what I need and keep them for up to three weeks before I plant them) to manage, I bought a mini greenhouse a few years ago. I got it at a local garden store for about $35. It’s just a set of shelves with a plastic tent, basically, but it acts as a less insulated greenhouse for all my annuals. I can vent the zipper as much as I want and close it completely at night to keep the heat accumulated during the day in. I have it in a relatively shady but bright spot outside the garage. I also employ the garden wagon for whatever doesn’t fit in the greenhouse.
|My hardening-off greenhouse filled to capacity.|
|Other plants, mostly perennials, go in a garden cart that I can easily move in and out of the garage when it is cold.|
The trick with hardening off is to gradually expose your plants to the conditions they will be living in. You can probably accomplish this in a week, but if you don’t have that much time, even a few days will help.
You might be thinking, “I buy plants and stick in the ground an hour later and nothing bad has happened.” That’s probably true. But I bet your plants didn’t do much growing for awhile and you might have even had a few crispy leaves. In other words, they survived but did they thrive?
So, yes, you CAN plant annuals (ones that are purchased, not ones you’ve grown from seed, which will most certainly croak if you don’t harden them off first) without hardening them off and yes, I’ve done it a few times myself. But for the next two weeks, when those plants seems completely frozen in time at best and pathetic looking at worst, I kick myself when I think that if I had just waited a few days to properly harden them off before I planted them, they’d be looking a heck of a lot better.