Light key to keeping geraniums in winter

I have about seven geraniums outside and have decided to save them this winter and replant them in the spring. I can put them on a table in a room with a large window with bright, indirect sunshine.

How should I care for them through the winter? Do I water them monthly or just when dry? Do they ever bloom in the winter? If I can get them to bloom over the winter, will they still bloom next spring? I’m just wondering what I can expect from these plants.

— Phyllis

The biggest challenge to wintering over geraniums is providing enough light for them. It’s surprising how much less light there really is in a brightly lit room indoors compared to even a shady spot outside.

That’s even more true in the winter when the sun’s angle is lower and less light gets through the atmosphere. You also lose some light through the glass of the window, plus you don’t get all the reflected light a plant gets sitting in the open outside.

Geraniums really, really, really need a lot of light. Contrary to the advice I usually give people about growing houseplants, you probably want these guys in the direct sun for a good part of the day.

Even though a geranium is a perennial plant (just not cold hardy for us), it will go through a semi-dormancy over the winter. It will keep its leaves, but may lose a few and it slows its growth down a lot. You may get some bloom, but it is usually sparse and sporadic (and don’t worry, they’ll bloom just fine next spring).

The second important thing about keeping these guys going over the winter is to modify how you water them. Indoors, you’ll have to water them a lot less often than you did outside. Part of that is because of the dormancy of the plant, but it’s also because of the change in environment. Temperatures are more moderate in the house than outside, and humidity can be greater.

All this adds up to watering the geranium deeply and thoroughly, just don’t do it nearly as often as you did outdoors. Poke your finger into the potting soil around the plant and check for some dryness before soaking it again. Fertilize them once or maybe twice a month with a good soluble houseplant type fertilizer as well.

Even doing all this right, you’ll often end up with a leggy, spindly plant toward the end of winter. Sometimes, the plant looks so bad that people will throw it away.

Providing it with the light and the care needed will help a lot in this, but you’ll want to pinch back the plant (or even cut it back if it needs it) three or four weeks before you plan on putting it back outside. This will encourage the plant to push out new sprouts, thickening the plant and giving it a running start on spring.

Our trumpet vine is finally growing beautifully this summer. I noticed it has seed pods on it. My question is, when the pods are mature can we plant the seeds? I didn’t know trumpet vines grew seed pods.

— Priscilla

Trumpet vine can be prolific producers of seed pods. Wait until the pods start to turn yellowish or brown before picking them. You can then let the pods dry thoroughly and harvest the thin papery seeds. 

The seeds will germinate better and more consistently if you give them a period of cold treatment called scarification. They need about two months of temperatures below 40 degrees to germinate well.

Most people harvest seed in the fall and store the seed in Ziploc bags in the refrigerator over the winter to plant in the spring.

Dennis Hill is the nursery manager at Bookcliff Gardens, bookcliff
gardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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