Several pots of young pepper seedlings, some with green leaves and some with purple.

Starting Vegetable Seeds Indoors: Why, What you Need and How

In recent weeks, many of us have transitioned from having a vague awareness of something bad happening out there in the world, to other people, to realizing that we ourselves need to make serious changes to how we live our daily lives, including how we get our food, how we cook and how we eat. As I placed my first grocery order in this new reality, my usual meal planning strategies of checking the sales and searching cookbooks for inspiration gave way to selecting ingredients that would store well, be versatile, and might be picked over by other shoppers. I filled my virtual cart with dried beans, canned sardines, relatively unpopular root vegetables like beets and fennel, and whatever flours were available.

The order took hours to complete due to unusually high traffic on the grocery store website, and I could feel a sense of panic setting in as I repeatedly refreshed the page. I placed the order and stepped into my pantry to find, tucked under grow lights, several seed trays of freshly germinated cold-hardy vegetable seedlings I sowed the week before. Mustard greens, bok choy, peas, and broad beans. In the midst of collective panic and uncertainty were the beginnings of what would be, in only a few weeks, sustenance. Growing food from seed has always felt like magic, but now it felt both vital and calming.

We’re unlikely to reach a point where everyone needs to grow their own food. There is enough food. But as our food supply chains clumsily adjust to rapid changes in the nature of demand, there will be gaps and inconsistencies in what is available. That said, nothing is certain, especially when our food system relies on exploiting the labor of its workers who - from farm laborers to supermarket employees - have suddenly become even more vulnerable.

Whatever happens, we will need to cook and eat more flexibly. We can’t rely on having the things we normally have, whenever we want to have them. Growing some of our own food is one way to manage this uncertainty if only through some small measure of self-reliance. If you are lucky enough to have the resources, time and energy to spare, now is the time to give it a try.  

Direct Sow VS Transplants

There are two ways to grow vegetables from seed: direct sowing and transplanting. The best method to use depends on what you are growing, your climate, the size and conditions of your garden, your budget and the amount of time and effort you have to give.

Direct Sowing

To direct sow seeds you simply plant them into your outdoor garden soil. If you live in a warm climate (between USDA Zones seven or eight and 13) it’s possible to direct sow pretty much anything, as long as you’re willing to wait for warm enough weather to begin your garden. If you live in a cool climate (between USDA zones two and six) there are some vegetables - like tomatoes, peppers and onions - that cannot be direct sown. They need a longer period of warm weather than you will have available, so you will need grow them from transplants.

Direct sowing is easier than transplanting; with minimal supplies and fewer steps, it’s beginner friendly. But, it gives you less control over the growing conditions of your seedlings, making it a less efficient, less productive, and riskier growing method. Direct sown, fewer seeds will germinate, and those that do will take longer and will be more vulnerable to pests and poor weather conditions.

Transplanting

To transplant, you plant small seedlings, that have already been growing for several weeks indoors, into your garden soil. You can either purchase transplants, or start them indoors from seed yourself. Though some plants prefer to be direct sown (like squash and cucumbers), almost anything can be started indoors as transplants, if done right, including root crops like beets, radishes and turnips. The main exception are vegetables with long taproots like carrots and parsnips, which need to be direct sown.

Unless you purchase your transplants, transplanting is more challenging than direct sowing. There are more steps to follow, and a long period of time during which you need to care for seedlings. If you are a brand new gardener, I recommend direct sowing as much as you can, and adding in a few transplants (like tomatoes) that you either buy or start yourself. Unless, of course, you anticipate enjoying the process of growing and caring for seedlings. Growing transplants from seed is one of the most rewarding parts of gardening and it greatly increases your garden’s potential for productivity.

Why You Should Consider Starting Seeds Indoors

Gardening is unpredictable. Starting transplants indoors gives you more control over your results. If done well, you can grow more food, more efficiently. In my garden, I start almost everything - with the exception of carrots - from seed. It can be an intimidatingly steep learning curve, but these are some of the reasons why I think you should consider starting more of your vegetables from transplants.

Extend your Growing Season

For the most part, vegetables don’t grow in freezing weather. If you live in a cold climate, your growing season is limited to the number of days between the first and last frosts of the year. Starting seeds indoors allows you to extend the length of your growing season, so that you can grow more food. In spring, seeds can be started indoors several weeks earlier than they can be planted outside. When air and soil temperatures warm up, you can transplant weeks old seedlings into your garden at a time when you would otherwise be sowing seeds and waiting for them to germinate.  

Increase Productivity with Succession Sowing

Vegetable transplants are normally available at garden centres only once per year, in early-mid spring. Such limited availability is based on the principle of growing vegetables as a singular, linear, process: you plant everything, watch it grow, harvest and then the growing season is over. Succession planting is a more productive approach that involves continuous propagation of seeds, and waves of transplanting, throughout your growing season.

When you grow your own transplants from seed, you’re in charge of when seedlings are available to be transplanted in your garden. You can plan for a garden with three main harvests instead of one - cool spring vegetables, long-season summer fruits and vegetables, and cold-hardy fall/winter vegetables - over a single growing season, and you can always have new seedlings waiting to fill spaces left by anything you harvest.

Pest resistance

Because they are so small, direct sown seedlings that have just germinated are easily eaten by pests - like slugs or birds - or damaged by unexpected poor weather conditions. Seedlings that are a few weeks old are less appealing to pests; they are stronger and more resilient, able to recover from a few nibbles. When you grow your own transplants from seed, and you learn to properly care for them, you can protect newly germinated seedlings inside until they are strong enough to fend for themselves outside.

Garden Planning & Design

Transplanting makes it easy to organize what goes where in your garden, which is especially useful if you are short on space. When spacing miniature plants, you don’t have to rely on your imagination to visualize where everything will go as much as you do when you are sowing tiny seeds. You can lay all of your transplants on top of your beds, move them around to get a sense of what you want to go where, and then plant. It might seem silly, but I find this strategy eases those feelings of overwhelm and uncertainty that can happen when you are learning to garden.

Supplies you will need to Start Seeds Indoors

Your seed starting setup can be elaborate or it can be scrappy, but you will need at least four things to start growing your own vegetables from seed indoors: seeds, growing medium, containers and light. A few additional pieces of equipment that, while not essential, increase your chances of success, are an oscillating fan and a heat mat.

Seeds

The best seeds to use are the ones you have, and seeds have become more challenging to find, so use whatever source you can. If possible, I recommend buying seeds from small local seed companies in your area. The varieties they sell are well suited to your climate. When deciding what seeds to buy, choose things you love to eat, and start with a relatively small number of mostly easy-to-grow plants. The easiest vegetables for you to grow will depend on your climate and garden space, but I recommend lettuce and most other greens, radishes, pole beans, summer squash, tomatoes and cucumbers for new gardeners.

Growing Medium

You need something to grow your transplants in. Seed-starting mix is the best option, but you can also use regular potting mix, though it tends to be much coarser and more difficult to work with, or you can even make your own. I use this PRO-MIX premium organic seed starting mix and this Fox Farm Ocean Forest potting soil. Under normal circumstances, you should never use soil from your outside garden to start seeds. Doing so risks bringing in disease and pests from outside. But if it is all you have right now, give it a shot.

Containers

There are so many options for materials and many sizes of containers, it can be overwhelming: plastic seed trays and cell packs, various biodegradable containers that can be planted with your seedlings, recycled or DIY containers, and soil blockers. For beginners I recommend using either the plastic seedling trays or recycled containers and inexpensive plastic or styrofoam cups. These are reusable year after year and save you the time required to make your own pots when you are already taking the time to learn to garden.

The sizes you will need depend on what you want to grow and how long they will need to be indoors before transplanting. The 6 cell packs are the most versatile for a minimal setup, most seeds can be started in them. If you are starting certain warm-season seedlings, like tomatoes or peppers, that grow indoors anywhere from six to 12 weeks, you will also need larger containers to pot them up into when they grow too big for the 6 packs. Three - four inch pots, or large plastic or styrofoam cups work well for this. If you’d like to save space, you may also want some smaller cell trays - I like these sturdy 72 cell plug flats - for cool season seedlings, like lettuce and kale, that only need to be indoors for three to four weeks.

Light

Save money with recycled containers, use inexpensive potting mix or garden soil if you must - but your transplants will not be successful if you do not use an indoor light. Don’t be fooled by pictures on the internet of seedlings growing in sunny windowsills. While you might be able to get away with starting some cool weather crops that will only be indoors for 3-4 weeks, like lettuce or kale, in the light of a window, that won’t be enough light to produce strong, healthy seedlings. Especially not for warm-season plants that will need to be indoors for 6-12 weeks, like tomatoes or hot peppers. If you want to grow your own transplants, you will need indoor lights.

You don’t, however, need to invest in expensive and complicated grow-light setups with lights produced specifically for indoor growing. Relatively inexpensive fluorescent or LED shop lights will work fine. Fluorescent lights work, but you need to be careful with them. They are dangerous if they break and are difficult to dispose of. I switched to LEDs a few years ago and am very happy with them. I currently use these lights.

Oscillating Fan

One of the biggest threats to indoor seedlings is damping off - a disease that causes them to suddenly flop over and die. The best thing you can do to prevent damping off is reduce the humidity and moisture around your seedlings. Allow the tops of your seed cells to dry out before watering and keep air circulating around the seedlings - as the wind would do if your seedlings were outdoors - with an oscillating fan. You can buy a mini fan and clamp it on the shelf holding your seedlings, or you can set one up you already have around the house, pointing towards your seedlings.

Heat Mat

Optimal germination temperatures for most seeds are higher than those needed for seedlings to grow. Room temperature is sufficient for germination of many seeds, and most seeds will germinate at room temperature eventually, they will just take longer. But the optimal germination temperature for warm season vegetables - like tomatoes, peppers and eggplants - is higher than room temperature. Using a heat mat speeds up the germination process and increases the germination rate of these warmer season crops. I’ve used this heat mat for years and love it. If you don’t have the budget for a mat, try using a warm place in your home - like the top of the refrigerator, on the dryer or above a radiator.

HOW TO PLANT VEGETABLE SEEDS

1) Moisten your potting mix.

2) Fill your seed trays or containers with potting mix. Scoop the moistened potting mix into the containers, filling them to the top. Then pack down the soil with your fingers - it should decrease in volume significantly - and fill the containers back up to the top with more potting mix. Make sure the containers are completely packed with potting mix so that there is plenty of growing medium to make contact with the seeds and provide enough nutrients for your seedlings.

3) Using a small dibber or pencil, poke holes in the soil of each cell or container. Drop seeds into the holes and cover with potting mix. Check the seed packet for information about the depth of the holes, the number of holes to make per cell, and the number of seeds to put in each hole. In general, though:

Depth: the optimal depth for most seeds is two-three times their   diameter. So, larger seeds should be planted deeper than smaller seeds. In my experience, most seeds will germinate eventually, even if sown too deeply, but sticking to this general guideline speeds germination time and increases germination rate.

Number of Seeds: Aim for 1-2 plants per cell. You can either cut the weaker plant off at the soil line after they germinate, or separate them when it comes time to pot them up or transplant them out. I always sow more seeds than I need. Germination is not always 100%, and it feels like a waste of time to wait for seeds to germinate, only to have to sow more if there aren’t enough. Individual seeds are cheap, and excess seedlings can easily be composted or given away.

4) Label your trays.

5) Bottom water your seed trays/containers. Fill a seed tray half-way with room temperature water and set the seeded cells packs inside the tray so that the bottoms of the cells are sitting in the water. The potting mix will soak up the water. As soon as the top of the potting mix appears dark and saturated, remove the cell packs from the water and drain away any remaining water. I like to empty the water back into my watering can to use later. Try not to leave the cell packs sitting in the water for longer than necessary.

6) Set seed trays aside to germinate. How you store your trays for germination depends on the seeds they contain. Check the optimal germination temperature of the seeds you are sowing on the seed packet. In general, cool season vegetables are fine to germinate at room temperature, and warm season vegetables prefer warmer temperatures, so put them on a heat mat if you have one; but most will germinate eventually at room temperature.

If possible, fill each seed tray with seeds that have similar temperature requirements, and will take roughly the same amount of time to germinate, so that the seedlings are easier to care for. I sow cool season crops like lettuce and radishes in separate trays from warm season crops like tomatoes and peppers.

7) As soon as seedlings emerge from the soil, remove them from any heat mats you are using and place them directly under your lights. Keep the grow lights 2-3 inches above the seedlings at all times (hanging your lights from adjustable clamps makes this easy), and leave the lights on for 16 hours a day, turning them off at night.

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