How to Prevent Frost Damage on Non-Dormant Hardy Plants
Most of the plants we ship are dormant from cold storage. However some are potted and are growing. The following is how to handle those leafed out plants.
Sometimes you might receive non-dormant plants that would normally be dormant and ready to plant outside. Our hardy plant greenhouses are kept to a minimum of about 28-30°F at night, but by February the day time sun can warm them up well into the 70’s. The resultant new growth is tender and can be damaged by freezing weather, especially below 28°F for more than a couple of hours. Most plants will put on a second flush of new growth after early frost damage, in about 4-6 weeks. To prevent frost damage on non-dormant potted plants you have received here are a couple of options:
Keep the plants where they will receive bright light and remain cool, but above freezing, until danger of frost is past. If you can keep the plants cool (32-50°F) their growth will be slowed down, so they won’t stretch as much, and the leaves will be a little tougher. Fertilize them lightly with a low to medium nitrogen fertilizer, such as fish fertilizer with kelp to supply micro nutrients, or maybe compost tea. The kelp fertilizer may improve plant tolerance to cold temperatures.
As the day time temperature you are holding your plants at increases so will the rate of growth of your plants. Provide supplemental light if the plants seem to be stretching or getting leggy, fertilize lightly as above.
If you are expecting night time temperatures to be mostly above freezing, with an occasional frost still possible, then you could go ahead and plant outside. Be prepared to put some frost protection over your new plants if necessary. A paper bag, spun-bonded floating row cover (such as Reemay), or a blanket (with support) will provide a couple degrees of protection.
Plants that have been actively growing indoors need to gradually get used to being outside in the direct sun and wind to continue to perform their best. Put them outside in a partially sunny location for a few hours a couple of days, then over the rest of the week gradually increase the time and decrease the shade until they spend the full day outside. After a week you can plant following instructions in the Raintree Nursery Owners Manual.