Every fall now for several years I have dug some of the rosemary in my garden, potted in growing medium, and brought it indoors.
Invariably, soon after I have brought it in, the leaves start to get covered with powdery mildew.
I can usually keep it alive by washing it frequently but it doesn't thrive.
It has been suggested that I should open a window every day and let it have fresh air but this is impractical as the temperature gets well below frreezing.
Could it be that I am keeping it too wet? When I pot it I soak it well to set the roots into the potting medium.
My two rosemary plants grow outdoors all year round (going on 8 years.) I keep them trimmed looking like little Christmas trees, no extra water, no fertilizer, they seem to grow well on neglect. They don't mind freezing temperatures. Rosemary doesn't grow well indoors, the more sun the better it grows. If growing indoors watch for spider mites.
Many people have asked how to overwinter Rosemary. A friend of mine, a fellow member of the New England Unit of the Herb Society of America, put this in our recent newsletter, the Pennyroyal Papers. I hope it helps someone :o)
Success with Rosemary by Deb Peterson
Rosemary can stay outside until the temps stay below 45°. It can withstand some frost (Don't let the pot freeze in the ground, though, so you can't dig it out).
Bring it into the coolest part of the house. Rosemary is happy with night time temperatures in the fifties or even the forties.
Give it as much light as possible.
A DRY ROSEMARY IS A DEAD ROSEMARY (not shouting, but emphasis). Don't let it dry out, but don't keep it too wet. Texas potting is the secret to this dilemma. (It is remarkable drought tolerant in the summer out in the garden) Texas potting is explained below.
If your rosemary should develop powdery mildew, spray lightly with a mixture of one tablespoon alcohol to a cup of water. Give it a chill outside on a warm winter day. Powdery mildew is due to a lack of air circulation.
Heat the steak fork and make a double row of holes around the bottom of the pot.
Make another row of holes just below the watering lip.
Put the perlite in the bottom of the pot to just cover the double holes around the bottom.
Pot up your plant with regular potting soil. Water well.
Put the potted plants in a water tight container and fill the container to any height to just above the bottom row of holes (this is a great way to leave plants when you travel).
The secret of this system is the upper row of holes. These holes supply air to the roots. Clay pots are porous and can be used without making air holes. If you use clay, put at least 2" of perlite in the bottom. This system also works well with cyclamens.
The main problem is that you are trying to grow something that is quite unsuited to your climate. If you must grow rosemary, treat it like an annual and replace it every spring.
The rosemary bush in front of my house is about 30 years old. It survived the "Great Freeze of '07" this past January, when temperatures turned my wax-leaf begonias to mush and killed my statice (sea lavender, Limonium perezii). Besides that record-breaking chill, we had a generally cold winter, with frost as early as the end of November. However, freezing temperatures here happen only at night. It's round-the-clock freezing for several days that kills rosemary.
Thanks for the suggestions - I do plant new rosemary every spring but I like to try to keep some going indoors over the winter, or for as long as I can.
For the person that suggested spraying with an alcohol mix - would that be ordinary rubbing alcohol?
In all the years of being a professional greenhouse grower did I ever experience a Rosemary plant which thrived indoors. Each year we'd buy rooted cuttings from a vendor and grow them for several weeks to establish roots and we carefully timed it so they were only in the greenhouse for about a month before being moved outside.
It's best to just buy a fresh plant each year. Rosemary does not get near enough air flow, sunshine or anything it needs to thrive indoors.
I agree. When I read about people who made it work, I think "pure luck".
The other issue with bringing plants indoors is bugs. Unless you drown the soil in some hideous chemical, you have NO idea what's living in it. A friend of mine liked to move houseplants outdoors for the summer and in for the winter, claiming she'd never had a problem. This year, her luck ran out. She's got mealybugs all over the place, not just on the plants that lived outdoors, but also on the ones that didn't.
It really all depends on the level of stress put on houseplants outdoors. Most of them are overwatered and that leaves them open for insect infestation. I have a few plants I put out for summer, my ficus trees and some others, but I carefully inspect them before I bring them indoors.
The only problem I've ever had an enormous infestation of were fungus gnats. Oh, and spider mites inside the greenhouse on the Brugmansia's. That is where I learned they do not like seaweed; that or the plants vigor got better andd weren't prone to spider mites to the point of major damage.
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