When and how to start your seeds

Tomatoes, like many vegetables, should be started inside and allowed to mature into seedlings before being transplanted outside. Starting seeds indoors results in higher germination rates and allows you to select the strongest plants for transplanting, resulting in more abundant, heartier adult plans.

Seeds ideally should be started roughly 4-7 weeks before the final frost. Average frost dates for your area can be found on the Old Farmer’s Almanac, among other sources. We’ve had success starting plants later than this, though results (like so much in gardening) will depend on the geographic area in which you’re located, the weather, and more.

Planting your seeds

We’ve found that the two best options for the “culture” that you initially plant your seeds in are seed-starting soil and coco coir pellets.

A seed-starting soil is a mix of natural components that provide nutrients aimed at encouraging seed germination while avoiding compacting the soil too much, which limits airflow to the roots, and makes germination more difficult. Many mixes of seed-starting soil are available at garden shops and online, and it’s also possible to make your own (an 8:1:1 mixture of rehydrated coco coir:vermiculite:perlite is a good starting point).

Coco coir pellets are dried discs of fiber from the husks of coconuts. These are rehydrated and used as the medium in which to start seeds. These are especially sustainable and widely available online and in garden shops.

We have started seeds using conventional potting soil in the past and still had good results, but prefer the other cultures for their improved germination rates and better suitability when it comes to starting seeds.

Regardless of what option you choose, sow seeds roughly 1/4 inch deep into your culture, lightly filling the hole above the seed with your chosen medium. If you are using seed-starting soil or potting soil, sow seeds 1 inch apart. If you are using coco coir pellets, plant one seed per pellet.

Caring for your newly planted seeds

You’ll want to keep your seeds warm and moist as they begin to grow: 75–85°F and humid but not soggy. Covering your planter with plastic wrap or a clear plastic lid will help lock in heat and moisture (we’ve also left our plants on our radiator when things get cold, but make sure the starting culture doesn’t dry out if you do so). During this period, you’ll want to provide your seeds with a strong light source; if living in a low-light environment, a grow light can be helpful.

Your seeds should germinate, in about 7-14 days, at which point you’ll have very tiny tomato plants! You’ll want to continue to care for them until they are ready to be moved into a slightly larger pot, which is known as “potting up.” A good rule of thumb is to wait until plants are 2 inches tall or they have developed their first “true leaf,” meaning the first leaf to emerge after the initial leaves from germination.

Potting up your seedlings

After your seedlings have reached 2 inches in height or have their first true leaf, you should transfer them into a larger pot to encourage root growth and further development. Be careful handling them at this point as their stems and root structures are very delicate (coir pellets can be transferred without removing the seedling since the pellets and their cases will break down in the soil). Seedlings should be transferred to 4-inch containers filled with well-drained potting soil.

In there new pots, plants should be kept roughly 60–70°F and you should continue proving a strong light source for your seedlings. As you allow your plants to grow in their new pots, you can feed them with fertilizer if you choose to do so, but make sure it’s diluted to at least 50% of its usual potency (e.g. if your fertilizer calls for 1 tablespoon of fertilizer per 1 gallon of water, use 1/2 tablespoon or less of fertilizer per gallon at this stage).

Roughly two weeks before you plan on planting your seedlings outside, you’ll need to start a process called “hardening off,” which simply means acclimating them to outside conditions. This will allow the plants to slowly adapt to the harsher outdoor weather (e.g. swings in temperature, heavy rain, etc.) that would otherwise be a shock to their system after their relatively cushy indoor life.

Hardening off your plants

When you harden off your plants, you place them outside for a set period of time before bringing them indoors, and repeat the process daily, extending the amount of time they spend outside each day. You can begin hardening off your plants when overnight temperatures are 45°F but the warmer things are (ideally 55°F) the easier it will be for your plants to acclimate and the faster you can harden them off. 10-14 days is an ideal period of time for the process, though it can be accomplished in 7 or fewer days; however, the less time you take, the greater the risk of shocks that can degrade or even kill the plant.

A strict hardening off calendar isn’t necessary, as long as you generally allow the plants more time outside each day, but we usually follow the below schedule in New York. If your area has more temperate spring conditions, you can accelerate it; if it has harsher conditions, you should take things more slowly. Local university agriculture programs are an excellent resource for gardeners and will often have information and insights about your particular region.

• Day 1: Place outside for one hour during warmest part of the day; indirect sunlight

• Day 2: Place outside for two hours during warmest part of the day; indirect sunlight

• Day 3: Place outside for three hours during the warmest part of the day; indirect sunlight

• Day 4: Place outside for five hours that end at warmest part of the day; direct sunlight

• Day 5: Place outside for seven hours that include the warmest part of the day; direct sunlight

• Day 6: Place outside for nine hours that include the warmest part of the day; direct sunlight

• Day 7: Place outside for 12 hours with the warmest part of the day at the timespan’s midpoint; direct sunlight

• Day 8: Place outside where you plan to plant seedling as soon as you wake up and bring in just before you go to bed

• Day 9: Place outside where you plan to plant seedling as soon as you wake up and bring in just before you go to bed

• Day 10: Place outside where you plan to plant seedling as soon as you wake up and leave all day then overnight

Transplanting seedlings into your containers

Once you’ve hardened off your seedlings, they’re ready to be moved into their final homes in their containers. You should still handle your plants with care since their stems are still fragile.

Tomatoes should be planted in containers that are at least 18 inches deep and 15 inches wide. Dig a hole that is slightly larger than the root ball of the plant and gently break apart the root ball before placing in the soil to encourage root growth. In general, the larger a container you use, the more your plant will thrive as its roots will have more room to grow and more nutrients to access due to the greater volume of soil. If using fertilizer, a high-phosphate fertilizer applied when transplanting this variety has had particularly good results.

It is recommended to add a tomato cage or stake at the time you transplant instead of later in the season to avoid disturbing roots and to give the plant a frame on which to train itself.

Caring for your plants

Tomatoes, like other bigger vegetables, require lots of sun and nutrients. Plans should receive a minimum of six hours of direct sunlight a day. We’ve been able to produce fruit with less sunlight, but it’s been fare sparser, and smaller, than under sunnier conditions.

Keep your plants well watered, but not oversaturated. Your containers should have drainage holes or other features that allow excess water to escape. Keeping soil too wet will result in root rot and kill your plants. Containers, due to their limited volume, dry out quickly, so check your planters often; at the hottest part of the summer daily watering might be required. If you stick a finger one inch into the soil and it’s dry, your plants need to be watered.

If fertilizing your plants with a conventional product, try to select one that that is heavy in phosphorus; nitrogen-heavy fertilizers encourage leaf and stem growth but at the cost of fruit production, and we want tomatoes, not leaves. Follow manufacturers instructions for all fertilizers but remember that under-fertilizing is better than over-fertilizing. Fertilizing seems to have best results at transplant and just before the plant puts out fruit. A well-sourced compost applied monthly is another good options: add about half an inch over the top of the soil before watering. Remember that tomatoes are heavy feeders, and the finite nutrients in a container often need to be supplemented throughout the growing season for best results.

Your plants are open-pollinating, meaning that they are pollinated the traditional way that we think of plants being pollinated: bees visiting flowers, wind moving pollen, etc. While even in an urban environment we haven’t had much issue with pollination, if you'r plants seem to be dropping a lot of flowers (i.e. a flower appears, but no fruit is produced) you might want to consider manually pollinating them. To do so, take a soft-bristled paint brush and gently brush the inside of a flower; then brush the inside of another flower with the brush; continue moving around until all the open flowers on the plant have been brushed. A less labor-intensive way to encourage pollination is to gently shake the plant—this will cause the flowers to express their pollen and hopefully the pollen in the air will pollinate the flowers.

Harvesting and storage

This variety takes roughly 75-85 days to mature, meaning the time from being transplanted into containers until they’re ready to harvest; weather conditions, care, nutrients, and other factors can extend this period. Tomatoes are at their best when fully ripe but can be harvested before that point: As long as the fruit have begun to change color (from green to brick red) they will continue to ripen off the vine. If you’re not planning on using tomatoes for some time, need them to travel, or won’t be able to attend to your plant for a bit, early harvesting is an option, though these are rarely as good as fruits harvested at peak ripeness. Keeping the calyx (essentially the leaves and stem that connect the tomato the plant) intact when harvesting will also extend their shelf life off the vine. Store tomatoes at room temperature and never in the fridge; most will last 4-7 days without issue.

Fast facts and technical jargon

• Scientific name: Solanum lycopersicum

• Determinate/indeterminate: Determinate

• Germination rate: 85%

• Life cycle: Annual

• Days to maturity: ~75-85 days

• Average size: 4-7 oz.

• Pollination type: Open pollination

• Eco-consciousness: Organic, non-GMO

• Starting window: Feb.-Apr.

• Days to germination: 7-14

• Adult heigh: 2.5-4 feet