Bury most of the stem, not just the roots, and if the transplant is tall and leggy, lay it sideways in a trench instead of a deep hole. Either way you are trying to get as much stem as possible underground, because that buried stem turns into root. The rest of this page walks through why that matters, when to do it, and how to avoid the mistakes that undo the benefit.
Why this matters
A tomato stem is not like most plant stems. Any part of it that ends up in contact with damp soil will sprout fine white roots along its length, given a little time and darkness. That means the depth you choose at planting is not cosmetic. It decides how large a root system the plant starts with, and a bigger root system means more capacity to pull water during a dry stretch and more anchorage once the plant is loaded with fruit and leaning against a stake or cage.
Skip this step and plant at the same depth the seedling was growing in its pot, and you get a smaller root mass than the plant is capable of building. In hot, dry weather that shows up as wilting by afternoon even when the soil isn’t fully dry, because the roots simply can’t keep up with what the leaves are losing. It also shows up later as a plant that rocks in the wind or topples under its own fruit load. The extra roots you get from burying stem are the difference between a plant that shrugs off a heat wave and one that sulks through it. This is one of the few places in tomato growing where doing more at planting time pays off for the entire season, which is why it’s worth doing properly before you move on to the rest of what’s in the tomato growing guide.
When to do it
This is strictly a transplanting-time job. You bury stem when you set the plant into the garden, not afterward, because once roots have established in place and the plant is settled, digging it up to replant deeper does more harm than good. The window is while the transplant is still young, flexible, and easy to lift without tearing its existing root ball.
Look at the plant itself rather than the calendar. A transplant that has stretched tall and thin indoors, with several inches of bare stem between the soil line and the first leaves, is telling you it wants the trench method rather than a simple deep hole. A shorter, stockier transplant with leaves close to the soil can usually just go into a deeper hole without any bending. Either way, the right moment is before the plant has flowered, since a plant that’s already setting blossoms has shifted its energy toward fruiting and doesn’t take well to having its root zone disturbed. If you’re working with a grafted tomato, timing matters even more, because there’s a second thing to watch for besides stem length, which the how-to section below covers.
How to do it
Start by stripping off the lower leaves and any side shoots along the section of stem that will end up underground. Leaves left on below soil level will rot in the dark, damp conditions down there, and that rot can travel up into the stem itself. Use your fingers or a clean pair of snips and pinch or cut each leaf flush with the stem, working from the base upward until only the top cluster of leaves remains.
The straight hole method
If the transplant is short and stocky, dig a hole with a trowel that’s noticeably deeper than the plant’s root ball, set the plant in so most of the stripped stem is below the surrounding soil line, and backfill around it, firming gently with your hands as you go. You want the soil in contact with the stem, not packed so hard it excludes air, and you want only the top leaf cluster showing above ground when you’re done.
The trench method
For a leggy transplant, dig a shallow trench instead of a deep hole, roughly the length of the buried portion of stem and just deep enough to cover it. Lay the root ball at one end and gently bend the stem so it runs along the bottom of the trench, then curve the top of the plant upward so the leaf cluster pokes out of the soil near the trench’s far end. Tomato stems are more flexible than they look, especially a couple of hours after watering, but bend slowly and support the stem with your other hand near the bend so it doesn’t snap. Backfill over the horizontal section, leaving only the top growth exposed, and firm the soil down.
Either method, finish with a slow, deep watering right at the base to settle soil around the buried stem and close up any air pockets. The plant should look a little squat and stubby compared to how it looked in the pot, with soil coming right up to the base of the top leaves. If you can still see bare stem standing above soil the way it did in the nursery pot, you haven’t buried enough of it.
- Strip every leaf and side shoot that will end up below the final soil line.
- Choose a straight hole for stocky transplants, a trench for leggy ones.
- Bend the stem slowly, supporting it near the curve, never forcing it.
- Backfill so only the top leaf cluster remains above ground.
- Water deeply right after planting to settle the soil around the buried stem.
What goes wrong
The most common failure is simply not burying enough stem, usually because the hole felt “deep enough” by eye. If you dig up a struggling plant later and find a short, shallow root ball with an obvious ring of stem sitting bare above the soil, that’s the cause. The fix next time is to strip more leaves than feels necessary and commit to a genuinely deeper hole or a full trench rather than a token dip.
The mistake that looks like extra care but isn’t is deep-planting a grafted tomato past its graft union, the visible knob or seam near the base of the stem where a productive top variety was joined onto a disease-resistant rootstock. Bury that union and the top variety will send out its own roots above it, which quietly cancels the entire reason you paid more for a grafted plant. Check the stem for that seam before you decide how deep to go, and keep it well above the soil line no matter which method you use.
Overwatering right after a trench planting is another one that masquerades as care. Soggy, waterlogged soil around a freshly bent and buried stem is an invitation to rot before new roots have had a chance to form, and it also draws in the soil-dwelling pests and pathogens covered on the tomato pest identification page. Water deeply once at planting, then let the soil surface dry somewhat before the next watering rather than keeping it saturated out of anxiety that the plant needs extra help settling in.
Doing it differently
Container-grown tomatoes still benefit from deep planting or trenching, but the limited soil volume means you should judge depth against the pot size rather than trying to match an in-ground trench. A five-gallon or larger container usually has room for a straight deep hole even with a fairly leggy transplant, since you can choose a bigger pot instead of bending the stem sideways.
Raised beds warm and drain faster than native garden soil, which makes them forgiving of deep planting because the buried stem sits in soil that’s less likely to stay cold and wet for long. That’s an advantage for trenching specifically, since the new roots along the buried stem form faster in soil that warms up quickly.
Spacing is where variety type changes the plan more than growing method does. Determinate varieties stay compact and can generally be set closer together, while sprawling indeterminate types left unstaked need considerably more room to spread than the same variety grown up a stake or cage, a difference worth sorting out before planting day by reading through the guide on staking and caging tomatoes. There’s no single spacing number that fits every garden, since it depends on the variety’s mature size, your support method, and the airflow your local humidity demands, so check the seed packet or your regional extension office for a figure suited to your conditions rather than copying a spacing you saw for a different variety.
Common questions
Can I bury a tomato plant too deep?
Not really, as long as you leave the top leaf cluster above soil and the plant isn’t sitting in waterlogged ground. The limiting factor is usually how much bare stem the transplant has to offer, not a risk of going too far.
Do I need to trench every tomato transplant, or only leggy ones?
Only the leggy ones need trenching specifically. A short, stocky transplant does just fine in a simple deep hole, and trenching a plant that doesn’t need it just adds extra digging for no real benefit.
What if my transplant already has flower buds when I plant it?
Bury as much stem as you comfortably can without disturbing the root ball too much, but don’t force a deep trench on a plant that’s already flowering, since the root disturbance can cost you those first blooms. A shallower deep hole is the safer call at that stage.
Will burying the stem cause stem rot instead of roots?
It can, but usually only in soil that stays cold and soggy for an extended stretch, or when leaves were left on the buried section to decay. Stripped stem in soil that drains and warms normally will root rather than rot.