Put compost or aged manure in the planting hole, along with a balanced fertilizer

The hole itself is your chance to give tomato roots an when ready advantage. Before you set the seedling in, fill the bottom 3 to 4 inches with finished compost or aged manure — material that has broken down completely and will not burn roots. This layer gives roots something nutrient-rich to grow into right away, rather than forcing them to search through plain soil.

On top of that, add a handful of balanced fertilizer — something like 10-10-10 or 5-10-5, mixed into the compost layer so it does not touch the stem directly. The middle number (phosphorus) matters most at planting time because it encourages root development. If you use a granular fertilizer, work it into the compost so it dissolves slowly as you water. If you use a liquid fertilizer, you can add it to your first watering instead of putting it in the hole.

Key Takeaways

  • Fill the bottom 3 to 4 inches of the hole with finished compost or aged manure to give roots when ready nutrition.
  • Add a balanced fertilizer (10-10-10 or similar) mixed into the compost layer, never touching the stem directly.
  • Bury the stem deeper than it was growing in the pot — tomatoes will root along the buried stem and develop a stronger plant.
  • Water thoroughly after planting so the compost settles and makes contact with the roots.
  • Avoid fresh manure, peat moss alone, or fertilizers touching the stem, all of which can damage young roots.

Why the stem can go deeper than the pot

Tomatoes have an unusual ability: they will grow roots all along a buried stem. This means you can plant the seedling deeper than it was sitting in its container — even up to the first true leaves. The buried stem becomes additional root tissue, which means a stronger, more stable plant that can pull water and nutrients from deeper in the soil.

This is one of the biggest advantages of the planting hole method. You are not just setting the seedling at the same depth it came in; you are using the hole to anchor the plant better and expand its root system. Bury the stem at least halfway, or even all the way up to the lowest leaves if the seedling is leggy (tall and thin).

How to layer the hole for best results

The order matters because you want roots to encounter nutrition gradually, not all at once. Start with 3 to 4 inches of compost or aged manure at the bottom — this is your base layer. Mix a handful of balanced fertilizer into this layer so it is distributed, not concentrated in one spot. If the hole is deeper than 6 inches total, add another inch or two of plain soil on top of the fertilizer layer before you set the seedling in.

This buffer layer prevents the roots from touching concentrated fertilizer when ready. Once the roots grow into the compost layer below, they will find the nutrients they need. Fill the rest of the hole with the soil you removed, water it in thoroughly, and the compost will settle as it absorbs water, creating good contact between roots and nutrition.

What not to put in the hole

Fresh manure is too hot — it will burn roots and can introduce pathogens. Use only aged manure that has sat for at least six months and has turned dark and crumbly. Peat moss alone holds water but provides no nutrition and can become hydrophobic (water-repellent) if it dries out. If you use peat, mix it with compost so it stays moist and adds some food value.

Do not put high-nitrogen fertilizers directly in the planting hole — they encourage leaf growth at the expense of roots and flowers. Avoid putting any fertilizer where it touches the stem; always mix it into the compost layer or add it to your first watering. Do not use synthetic potting soil alone in the hole — it drains too fast and does not hold nutrients. Save potting soil for containers; use compost or aged manure for in-ground planting.

Adjusting the hole for your soil type

If your native soil is heavy clay, the compost layer becomes even more important because it creates a pocket of better drainage around the roots. Use 4 to 5 inches of compost in a clay hole, and consider mixing a little perlite or coarse sand into the compost to keep it from compacting. If your soil is sandy and drains too fast, use aged manure instead of compost — manure holds water better and breaks down more slowly, feeding the plant over a longer season.

In either case, the principle is the same: you are creating a transition zone between the planting hole and the surrounding soil. The compost or manure is richer and holds moisture better than plain soil, giving the young roots time to establish before they have to work in the native soil around them.

Watering after planting to settle everything

After you fill the hole and set the seedling in place, water thoroughly — not a light sprinkle, but enough water that the soil darkens and settles. This accomplishes two things: it removes air pockets around the roots, and it activates the fertilizer so it begins to dissolve and become available to the plant. The compost will compress slightly as it absorbs water, creating better contact between the roots and the nutrition you added.

Water again the next day if the soil surface feels dry. For the first week, keep the soil consistently moist but not waterlogged. After that, tomatoes prefer to dry out slightly between waterings — this encourages deeper rooting and stronger plants. Mulch around the base with 2 to 3 inches of straw or shredded leaves to hold moisture and keep the soil temperature steady.

Frequently Asked Questions

Can I use kitchen compost from my bin?

Yes, if it is finished — dark, crumbly, and no longer hot to the touch. If it still smells like fresh food scraps or has recognizable pieces in it, let it sit another month or two. Unfinished compost can introduce mold and pests, and it will heat up as it breaks down, which can damage roots.

What if I do not have compost or aged manure?

You can plant without it, but the seedling will grow more slowly at first. If you have nothing else, dig the hole, add a balanced fertilizer mixed into the native soil, and water in well. The plant will survive, but it will not have the head start that compost provides. Plan to side-dress with compost or fertilizer once the plant is established.

Should I add lime or sulfur to adjust pH in the planting hole?

Not in the planting hole itself — it will not mix evenly and can create pockets of wrong pH right where the roots are. If your soil pH is off, amend the whole bed before planting, or add lime or sulfur to the surface and let it work in over time. A soil test from your local extension office will tell you what your pH is and what you actually need.

Can I use slow-release fertilizer pellets in the hole?

Yes, slow-release pellets work well in a planting hole because they feed the plant gradually over weeks or months. Mix them into the compost layer so they are not concentrated in one spot. Follow the package rate — usually a tablespoon or two per hole — and do not exceed it, because slow-release fertilizer still burns roots if too much is present.

How deep should the hole be if I am planting a very tall seedling?

Make the hole deep enough that you can bury the stem up to the lowest true leaves, even if that is 8 or 10 inches deep. A leggy seedling actually benefits from deep planting because the buried stem will root along its length, creating a much stronger root system than a shallow plant would have. The extra depth is an advantage, not a problem.