First, what's this determinate vs. indeterminate stuff? Does it matter?
Yes it does. You need to know what kind you have before you plant.
- Determinate tomatoes are smaller plants, bear fruit for a shorter time, and sometimes don't need staking to hold them up. (The no-staking part isn't always true, depending on how prolific they are and how big their fruit is.) You can plant these in slightly smaller pots and not suffer too badly for it, but you do still need to give them space.
- Indeterminate tomatoes tend to be much larger - they grow bigger and bloom for a longer season than their determinate cousins. They definitely need staking, and they can only be grown in really large pots. Most of the great varieties seem to be indeterminates.
What do the numbers mean?
When someone describes a variety as "indeterminate, 75 days", that means that it will bear ripened fruit about 75 days after transplant. So even if it's been in your dining room window sill for a month, the clock doesn't start ticking until you've got it in its pot.
It's good to get a mix of early season and late season tomatoes. Early season tomatoes will have numbers ranging from 55 - 70. Late season tomatoes will be more towards 85 or 90 days from planting. Middle is, um, in the middle. Get a good combination and you'll have something ripening from July through the end of October.
Is there any advantage to getting them in the ground earlier rather than later?
Doesn't seem to be, at least in Seattle. (I suspect this is different elsewhere in the country.) They'll survive being planted a little early, as long as there's no frost, but in my experience it seems like they just go dormant until about the second week of May anyways and don't grow, bear, or ripen any sooner than tomatoes planted mid-May. I plant mine about the first week of May - right now.
How do you plant a tomato in a pot?
1. Get a big pot, at least fifteen gallons. If your varieties are determinate, you might be able to go a little smaller, but for big, sprawling indeterminates, you need large pots. I use medium-sized half-barrels for most of mine, and a few specialty pots from Gardeners' Supply.
2. Get a good soil mix - nothing fancy, just half compost, half potting soil, one handful of a good tomato fertilizer. I use this one.
3. Carefully strip the branches off the lower half of your tomato start so that you have a long, skinny stem.
4. Add the plant, burying it up to its little neck:
- If your pot is deep rather than shallow and wide, dig a deep hole and insert your tomato plant so that only its top few inches are above ground. All of the stem that's below ground will sprout roots, giving you a great root system, and the above ground stalk will shot back up in no time.
- If your pot is shallow and wide, it's a little trickier. Dig your hole to the bottom and then sideways, and set your plant in almost on its side and off center, gently angling it so that the stalk emerges from the soil at about the center of the pot. Be careful or you'll end up snapping it in half! Place the plant in at an angle and then brush dirt up against it to help return it to an upright position rather than actually trying to bend the stalk.
At first it will look like it's growing crooked, but it will straighten up in a few days as it finds the sun, and again you'll get a great root system.
- Water deeply.
Any other tips for success?
- Pull off suckers religiously for potted plants. For one, this keeps your plants to a more manageable size, and for another, you want your plants to focus on growing fruit, not growing many, many leaves. Here's a great guide to pruning to help.
- Don't fertilize too much -- fertilize when you plant, and maybe a light topdressing once more when they start to set fruit. If you add much more, your tomato plant will grow huge, beautiful, dense foliage that will be the envy of all your neighbors... but much less fruit. We don't care about the leaves. We want tomatoes. Right?
- Water twice a day when it's hot - August and September for sure. Tomatoes in pots need more watering than tomatoes in the ground. I soak each pot twice in a single watering. More than that and they tend to crack.
- Don't water too too much in late spring and early summer, especially here in Seattle where it rains on and off through June. Let them dry out just a little between waterings, then water again.
- Don't wait too long to put your stakes or cages in. Last year I put it off for much too long and couldn't get all of them properly caged. This year I put them in the day I planted, even though the tiny little plants won't need them for some time. Better safe than sorry.
- If you're using red plastic mulch (which I like), don't put it in until mid-June. Here in Seattle, it rains so much prior to that that I've had pots grow fuzzy white mold underneath the plastic if its set out prior to that. I don't know if it hurts them or not, but that year wasn't my best season ever so I think it had an effect.
I'll add to this list as I think of more.