Ask a Master Gardener: Grow geraniums from seed at home
Get a jump start on your geraniums this winter.
Q: Can I start geraniums from seed indoors? I put out lots of pots of geraniums every summer and I was wondering if I could save money growing my own. Any tips for doing this?
A: You can indeed grow geraniums at home from seeds, and it’s a fun late-winter project.
Whether you’ll save money is another question. It depends a bit on whether you invest in some of the tools most likely to bring you success.
One of the master gardeners in our group has had great luck starting geraniums near a sunny window in her dining room. But you may have better success starting seeds if you grow them under lights.
Geranium seedlings want bright light, but a sunny window may be too hot — or too cold — and a Minnesota winter window does not offer as many hours of light as geraniums prefer. If they don’t get enough light, they can become leggy and spindly.
If you choose to use lights, you’ll also want to buy a timer you can plug the lights into so the seedlings get eight hours of darkness every day. You’ll need some containers, some trays, and a soilless seedling mix. And if the room you plan to grow them in isn’t 70-75 degrees, you may get better germination and growth if you invest in some seedling heat mats. You can find these in garden catalogs.
That means you may spend more than the cost of several geranium plants from the greenhouse on your seed-starting equipment, but you can use this equipment for many years — and for starting other seeds. And the lights and containers you get don’t need to be pricey.
You can just set up a fluorescent shop light or two. Hang the lights from chains that you can raise as the plants grow. You can use many things for containers, such as empty milk cartons or plastic salad mix tubs, as long as they have been cleaned and sanitized and have drainage holes.
In our region, geraniums need to be planted in mid-February — much earlier than most vegetables you might want to start from seed — so you’ll want to start gathering supplies and ordering seeds now.
Wash any dirt off of your planting containers and trays and then soak them in a solution of one part bleach to nine parts water. It’s a good idea to wipe down your shelf with that bleach solution, too, especially if it has been used for other plants or garden pots. You’re trying to prevent “damping off,” a fungus or mold that can wipe out your seedlings.
Rinse the bleach solution off the containers and fill them with moistened seed-starting medium. Get the kind that does not have fertilizer added; plants should not be fertilized until they have begun to grow true leaves. (The first two “leaves” are not really leaves, but cotyledons.)
Sow the seeds a couple of inches apart and cover with about 1/8 inch more soilless mix. Set the containers in a tray of warm water to wick up moisture, then lift them out of the water and seal them in plastic bags to hold the moisture in. Put these bagged containers under your lights. The lights should be hung so that they are just a few inches from the tops of the containers, and then moved up as the plants grow so they are always just a few inches from the tops of the seedlings.
The seedlings should appear after a week or so. Once they do, remove the container from the bag and set it in the tray. From here on out, you want to water by pouring water into the tray and letting the potting medium wick it up. Let the surface dry out a bit between waterings. Don’t leave the plants standing in water. Once they have two true leaves, you can transplant the seedlings to individual containers.
Before you set the plants outside this summer, you will need to harden them off by gradually exposing them to outdoor conditions. Start with an hour a day in a shaded, protected spot and work your way up over a week or so to placing them in full sun. They’ll develop a tough cuticle that plants grown indoors don’t have.
It’s a bit of work, but growing geraniums is a delightful project, adding a splash of green to the last months of winter. Good luck!
Written by U of M Extension Master Gardeners in St. Louis County. Send questions to firstname.lastname@example.org .