January caught many of us, including growers, off guard with an unexpected hard freeze. After weeks of warm winter weather, the temperature dropped 50 degrees in a few hours. Overnight temperatures dipped to 21 degrees in the Heights with a wind chill in the teens. The prediction was only to dip to 27 degrees. When I checked at 2am that Saturday morning it was 23 degrees and it was still 23 degrees at 9am. This is our fountain on Saturday. We should have drained it so it would not crack. Thankfully it is very sturdy and suffered no damage, perhaps the egg lights helped. The Giant walking irises behind did a death march turning completely brown over the period of two weeks. That was hard to watch!What was unusual about this freeze? Most winters we get freezes in Houston. The difference is we see more damage when the plants are not prepared. As temperatures traditionally get cooler in autumn and winter, plants get the message to go dormant, harden off and rest till spring returns. Even plants that we covered wilted in the sustained long cold. As the days went on this poor cyclamen turned in to a pile of mush. We saw more damage this year because the plants were still growing with all the spells of warmer weather we had in December. Now we need to see what survived and what is permanently gone. You may already be seeing regrowth from many plants by now. In the end, only time will tell.Until we are sure we are past the last frost for this year we recommend leaving the dead leaves and branches, unless they are soggy and rotting. The dry leaves and branches can help protect the roots during another freeze. Remember the roots need to continue to get regular water and oxygen. If the plant has turned into a mushy mess, you need to remove that part asap. You will find this with tropical and succulents. Unfortunately, many of those may not survive. Once you remove the wet plant matter put mulch on top of those roots to help protect them. We recommend using a mulch that will compost to help protect plants before winter and summer. Managing root health is key to having healthy plants. We recommend a seaweed drench on all your plants before a freeze to protect them or after one to help them recover.This is a picture of our Doritis orchid in recovery. I forgot about it and its juicy leave have been turning to mush so I have been removing them. Now almost a month later it has some leaves coming back so I know it is alive. Thankfully, all is not lost because many plants are root hardy. This means the roots are alive and capable of putting up new growth. With tender perennials and vines, it is like getting a fresh new plant. Keep in mind that some plants take longer before re-growing than others. I have seen plants wait till May or June before venturing out from the roots. Once we are sure we are past any chance of freeze you can cut off all the dead part of the plant. Below on the right is a picture after the freeze. We did remove all the dead leaves and branches of the Blue Sky Thunbergia vine because it was rotting and not dry. On the right is how it looked last fall. It has frozen to the ground twice before so we expect it to return. It will take two years to look this full. Grasses are a bit different, if you plan to cut off the dead you can do it as soon as you see them sending up new green blades. Larger woody perennials that we have enjoyed for their shape and structure and now suffer frost damage will take time and training to regain their former stature. You can check if they are alive by scratching the bark. If it is soft and green underneath the plant is alive. Once you are sure what part is dead you can trim that part off. Keep in mind pruning stimulates new growth so waiting till we are past all possibility of freeze is prudent. It is important to fertilize when you are done so the plant has the nutrients to regrow. We recommend an all-purpose organic fertilizer which can be used year-round here in Houston. If you live in the Gulf Coast and have questions you can email us though our website http://www.ravenscourt.us
Our Ablution, Red Vein Chinese Lanterns, dropped most of its leaves after the freeze. This is a picture I took today. It is working hard to put out new growth. We hope we don’t have another freeze that knocks it back again. The last frost date for Houston is usually between Feb. 21 and March 1oth depending on which side of the I-10 you live on. Zone 9a and 9b are more or less separated along the I-10. Here is a map of Texas with data on last frost dates. Personally we like waiting until spring to do anything radical. Patience will mean replacing fewer plants!