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Getting ready for spring: A start-up guide for growing tomatoes indoors

The start of a tomato plant that will be transplanted in the garden at a later time is growing in the window.
AHPhotoswpg/Getty Images
Give your tomato plants a head start indoors. Put seeds in germinating soil under full-spectrum lamps four to six weeks before replanting them outdoors in spring.

Tomato plants need four to six weeks of indoor growing before they are hardy enough to be transplanted outdoors.

Back-time that to when the soil is warm enough in Vermont in mid to late May, and that means that late March or early April is prime time to start tomatoes indoors.

Begin to gather what you need now, though, so you'll be ready to go come seed-planting time in a couple of weeks.

You'll need 2-inch pots, some soil, tomato seeds, plant markers and a waterproof pen - to write down which variety seed is in each pot - and grow lamps.

If you still have some seeds from last season or even from years ago (perhaps you're hanging on to them because they are your favorite tomato variety and you want to replant), first, try a germination test. This will show if the seeds are viable.

To do the test, take about five or 10 seeds, and place them in a moist paper towel. Put the paper towel in a plastic bag and set it in a warm spot out of direct light and let them germinate for a week.

If fewer than 80 percent of those seeds germinate, throw those out and purchase some new, fresh seeds.

Next, fill several two-inch pots with moistened germinating soil mix. Germinating soil is finer, which makes it easier for small seedlings to germinate and push through. Place two seeds in each pot.

And in this case, sunlight won't be enough to help your tomato seedlings grow. They'll turn leggy, thin and spindly. For short, stocky and strong tomato seedlings, place them under grow lights.

Keep the lights directly above the seedlings and once each day, brush your hand back and forth against the seedlings 10 times to stimulate growth.

For added warmth, try placing a waterproof heating mat underneath the plants, too.

As they germinate and grow, thin each pot down to just one healthy, strong seedling.

Then, when the height of each tomato plant is about six inches tall, transplant it into a pot that is one size larger. This will give it room to grow even bigger and also help the tomato seedling get its roots established.

When the weather and soil in your garden or raised bed has warmed enough in mid to late May, transplant them.

Using these techniques will help ensure you have strong and sturdy tomato plants, ready for the weather and better able to produce fruit.

Q: I was recently given a clipping of a purple passion vine. I was wondering what the best soil and pot size to plant it in is. - Kyle, in Andover

A: Your purple passion vine will need a lot of sun. If you have a heated or unheated green house or sun porch, that would be an ideal starting place.

And passion vines tend to like a smaller pot or container. They are okay if they're a little root bound.

The vine will do fine with regular potting soil and good drainage. You can achieve that by adding in some extra perlite to the soil mix.

Once your passion vine is growing indoors and the weather gets warmer in the summer, try to move it outside in plenty of sun.

Place it near a stake or cage so the vine can climb. Then by late summer or early fall, you should get some beautiful purple passion vine flowers.

All Things Gardening is powered by you, our audience! Send your gardening questions and conundrums and Charlie may answer them in upcoming episodes.

You can also leave a voicemail with your gardening question by calling Vermont Public at 1-800-639-2192.

Hear All Things Gardening during Weekend Edition with Vermont Public host Mary Williams Engisch, Sunday mornings at 9:35.

Have questions, comments or tips? Send us a message or get in touch by tweeting us @vermontpublicWe've closed our comments. Read about all the ways to get in touch here.

Mary Williams Engisch is a local host on All Things Considered.
Charlie Nardozzi is a nationally recognized garden writer, radio and TV show host, consultant, and speaker. Charlie is the host of All Things Gardening on Sunday mornings at 9:35 during Weekend Edition on Vermont Public. Charlie is a guest on Vermont Public's Vermont Edition during the growing season. He also offers garden tips on local television and is a frequent guest on national programs.