Tomato (Rainbow)

Big Rainbow is an open-pollinated heirloom indeterminate slicer that goes in after the Mar 28 last frost, climbs and branches all summer with light sucker management, and over a long 80-90 day season delivers huge 1-2 lb bicolor beefsteak fruit right up until the Nov 12 first frost cuts it down.

1. 1

   Sowing Seed Indoors

   Late Jan to mid-Feb, about 6-8 weeks before the Mar 28 last frost

   You'll see Seeds are flat, tan-yellow ovals. Within 5-10 days at 70-80F you will see a pale hook-shaped stem push up, followed by two smooth oval seed leaves (cotyledons), not the true ferny-edged tomato leaf yet.

   Do Sow 1/4 inch deep in seed-starting mix under grow lights kept 2-3 inches above the tray, with gentle bottom heat if the room is cool.

   Details
2. 2

   Seedling and Hardening Off

   Weeks 2-8 after sowing, roughly mid-Feb through late Mar

   You'll see By 4-6 weeks the plant has several sets of true leaves and a sturdy central stem about pencil width. Leggy, pale, stretched seedlings signal too little light.

   Do Pot up to a larger container once roots fill the starter cell, and begin hardening off outdoors 7-10 days before transplant.

   Details
3. 3

   Deep Transplanting Into the Bed

   After Mar 28 last frost, once soil has warmed and nights stay above 50F

   You'll see A healthy transplant ready for the ground is 8-12 inches tall with thick stems and 4-6 true leaves; the lower leaves may look slightly yellow if the plant has been in its pot too long, which is fine since they will be buried anyway.

   Do Strip off the lower leaves and bury two-thirds of the stem, either straight down in a deep hole or sideways in a shallow trench, so only the top rosette of leaves shows above soil.

   Details
4. 4

   Establishing and Early Staking

   Weeks 1-3 after transplant, roughly early to mid-Apr

   You'll see New growth at the top of the plant resumes within a week; leaves are deep green and turgor is firm in the morning. Wilting only in the hottest part of the afternoon that recovers by evening is normal, but wilting that persists overnight signals a watering or transplant-shock problem.

   Do Water deeply 2-3 times a week rather than a little every day, and begin tying the main stem loosely to its cage or stake as it grows.

   Details
5. 5

   Vegetative Growth and Sucker Pruning

   Weeks 3-8 after transplant, roughly mid-Apr through late May, and continuing all season

   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, quickly turning this large heirloom into a dense, sprawling tangle.

   Do Pinch out suckers weekly with your fingers while they are small (under 2-3 inches), keeping the plant trained to 1 or 2 main leaders tied to the stake or cage.

   Details
6. 6

   Flowering and Hand Pollination

   Weeks 6-10 after transplant, roughly late May through June, then continuing in flushes all summer

   You'll see Small yellow star-shaped flowers form in clusters (trusses) along the stem. Each flower has both male and female parts, and pollen sits inside a cone around the pistil until it is shaken loose.

   Do On calm days with little wind or bee activity, gently vibrate each flower truss by hand or with an electric toothbrush for a few seconds to release pollen onto the stigma.

   Details
7. 7

   Fruit Set Through Harvest

   Roughly 80-90 days from transplant to first ripe fruit, then continuing to first frost, roughly late June through early Nov

   You'll see Green fruit swells slowly into enormous globes, often reaching 1-2 lb, then ripens unevenly from the blossom end, developing a striking bicolor pattern of yellow and orange flesh with red marbled streaks, often with green shoulders remaining near the stem even when the fruit is ready.

   Do Harvest at good color development and full give when gently squeezed rather than waiting for the green shoulders to fully disappear, and keep tying the growing leader to its support as new heavy fruit sets continue up the plant.

   Details
8. 8

   Seed Saving by Wet Fermentation

   Peak season, when the best-looking fruit from your strongest plant is fully ripe, roughly Aug through Sept

   You'll see A fully ripe, unblemished Big Rainbow fruit with good bicolor development 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