Hello! This is what I posted in my local facebook group and someone recommended to ask here. Thanks a lot for your time! P.S. We’re in Hereford Zone “ I have a gardening question, I hope someone with experience can answer. I planted morning glories in the window box containers on Friday and left them out on the deck, remembering the “no frost” rule and now I’m getting conflicting information online. I soaked them for 24 hours prior to planting, just fyi. With these couple of nights in low thirties did I already kill them? Should I still bring them inside the garage? Leave them out? Any practical advice would be helpful. Thank you!”
Baltimore County Maryland
We're uncertain as to whether or not you planted Morning Glory seeds or pre-started plants (which are often not available at nurseries quite this early). Seeds can benefit from soaking to kick-start germination if recommended on the seed packet, but if you soaked a rootball, this is risky for root health. While Morning Glories consist of several species with a range of tolerances, it's likely these seeds (if that's what was planted) will be fine. While the parent plant often dies during winter, seedlings are known to reappear in following years in our area, having survived the winter. (Sometimes they are tenacious enough to be weedy.) Seed packets give guidelines as to when to sow the seeds in relation to a last-frost date (around mid-May in central MD); this can be done earlier if started inside until that date.
Containers are susceptible to more drastic temperature (and moisture) swings than in-ground soil, so in that sense, extra protection for the containers the Morning Glories were planted in may be sensible. Even so, a brief overnight dip into the low 30s is unlikely to cause any problems. If we see colder temperatures or a prolonged period below freezing, then protection in a garage wouldn't hurt.
If you planted pre-started plants, these are often greenhouse-grown and less tolerant of freezing temperatures; in that case, they would benefit from a bit of protection during the same conditions mentioned above. Frost-damaged foliage tends to show symptoms quite quickly for tender plants such as this, so if they were already singed, you would be able to tell and know to protect them going forward.
Thank you very much for your response! I pre-soaked and planted seeds from the packets. There was a variety of colors in each packet a as well as moonflowers mixed in in each container. Out of extra caution I decided to place containers in giant storage zip bags that I usually use to store bedding in. Thanks again!
You're welcome. If the bags are intended to provide a couple degrees worth of cold protection, that may help, but they also may rise in temperature too much if left out in the light. Opening them to promote airflow would be important to avoid mold, of which some fungi can kill germinating seedlings. (They cause what is known as "damping-off.") Instead, simply moving the pots indoors during sub-freezing nights should be all that is needed.