Tomato (San Marzano) New · Sep 2026

San Marzano is an Italian heirloom indeterminate paste tomato that normally goes in after the Mar 28 last frost and fruits continuously to the Nov 12 frost, but the two plants Luke added Sept 13 are going in late with only about 60 days left before frost, so this guide leads with that late-season push: sunniest spot, hard pruning to focus energy, and picking anything colored before the cold hits.

1. 1

   Late Sept 13 Planting: Racing the Frost

   Transplanted Sept 13, 2026, with roughly 60 days left before the Nov 12 first frost

   You'll see A young transplant with 4-6 true leaves going into soil that is still warm from summer but with a shrinking daylight and heat window ahead of it.

   Do Put both plants in the sunniest spot available, a 15-20 gallon grow bag or pot each, or the east edge of Bed A, stake immediately, and pinch suckers hard from the start so energy goes to the first two flower trusses rather than new vegetative growth.

   Details
2. 2

   Sowing Seed Indoors (Normal-Season Timing)

   Late Jan to mid-Feb, about 6-8 weeks before the Mar 28 last frost, for a full-season planting in future years

   You'll see Seeds are flat, tan-yellow ovals. Within 5-10 days at 70-80F a pale hook-shaped stem pushes up, followed by two smooth oval seed leaves (cotyledons), before the true serrated tomato leaf appears.

   Do Sow 1/4 inch deep in sterile seed-starting mix under grow lights kept close to the tray, with gentle bottom heat if the room is cool.

   Details
3. 3

   Deep Transplanting Into the Bed

   In a normal season: after Mar 28 last frost, once soil has warmed

   You'll see A ready transplant is 8-12 inches tall with a thick stem and 4-6 true leaves.

   Do Strip the lower leaves and bury the stem deeply, either straight down or in a shallow trench, so most of the buried portion can root.

   Details
4. 4

   Vegetative Growth and Hard Sucker Pruning

   Weeks 3-8 after transplant in a normal season; from day one for the late Sept planting

   You'll see The plant sends up new shoots (suckers) from the crotch where each leaf branch meets the main stem. Left alone, every sucker becomes its own leader with its own leaves and flower trusses.

   Do Pinch out suckers weekly, training to 1-2 main leaders; for the late Sept planting, prune harder than usual, removing essentially all side growth so the plant's limited remaining season goes entirely into the first trusses that have already set or are about to.

   Details
5. 5

   Flowering

   Weeks 6-10 after transplant in a normal season; within the first couple weeks for the late Sept planting

   You'll see Small yellow star-shaped flowers form in clusters (trusses) along the stem.

   Do Let bees and wind handle pollination outdoors; hand pollinate by gently vibrating trusses in a screened bed or hydroponic setup.

   Details
6. 6

   Fruit Set and Racing the Frost

   For the late Sept planting: whatever sets over the following weeks, through the Nov 12 first frost; in a normal season, continuing from midsummer to frost

   You'll see Oblong, thick-walled paste fruit with a pointed blossom end swells slowly; San Marzano's classic shape is longer and narrower than Roma, with fewer seeds and thicker flesh.

   Do For the late planting, watch closely as frost approaches and pick any fruit showing color, even a blush, before a hard freeze; ripen these indoors on a windowsill or in a paper bag rather than leaving them on the vine.

   Details
7. 7

   Seed Saving by Wet Fermentation

   From a fully ripe fruit in a full season, or from the best fruit the late planting manages to ripen

   You'll see A fully ripe, elongated San Marzano fruit with no cracking is the right pick; the seeds inside sit in a gel sac that must be broken down before drying.

   Do Scoop seeds and gel into a labeled jar with a little water, let it ferment a few days until a mold film forms, then rinse and dry the sunk seeds thoroughly before storing.

   Details

Techniques — transplant, prune, propagate, divide, seed