Garden Planning Part 3: How To Start Seeds Indoors

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This is part three of my garden planning guide. For part one all about deciding what to plant, click here. For part two, all about planning your garden layout, click here. For part four, how to companion plant, click here.

Today we’ll cover when to start seeds indoors, how to germinate seeds, my favorite seed starting supplies and more.

I love growing my vegetable garden from seeds. What could be more gratifying than watching your plants grow from one tiny seed into a full grown plant ready to harvest? It is so fulfilling to nurture and care for these tiny bits of life and bring them to maturity.

I also love to feel the tie back to my ancestors through this process of growing. I know that not too many generations ago, my relatives would have tended their own little garden to support their family and put food on the table. I have combed through old family photos endlessly searching for evidence of this connection, but so much was lost through time. Considering industrial agriculture is a fairly modern concept though, it’s safe to say that the vast majority of our relatives have grown food at some point in their past. I feel this connection and find my way back to these ancestral roots through the soil.

How to start seeds Indoors

Let’s start with the basics: For many plants, you don’t need even technically need grow lights to start seeds for your garden. You can use winter sowing in milk jugs outdoors, or try starting seeds in egg cartons and even toilet paper rolls. I’ve tried all of these with mixed results. My method of choice used to be soil blocking. Soil blocking is just compressing soil into cubes using a mold and planting directly into that cube without any additional containers. Then you can bottom water those seedlings and build nice strong root structures with zero waste. This method words great for producing strong plants, but it comes with a learning curve that can make it frustrating as you need exactly the right type of soil, and I find it really hurts my hands and is too strenuous.

I’ve been starting seeds using seed cells and trays, but often these are not built to last, and in order to keep plastic out of our landfills and reduce the frustration that comes with cracking cells and flimsy trays, I’ve upgraded my seed starting setup with these extra durable seed starting trays.

Each individual cell in these trays features an air pruning side slot on all four corners to discourage root circling and encourage better root growth.  The bottoms of each cell are also open providing air pruning at the lower end of each cell. Large, convenient finger holes in the bottom of each cell make it easy to remove seedlings when you're ready to transplant.

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If you’re growing heat loving crops like peppers and eggplant, you should also grab a heat mat for each tray.

So now that you have your tools, how do you know when to start planting seeds? Start too early, and your plants will outgrow their indoor containers before it is warm enough to move them outdoors. Start your seeds too late, and your plants won’t be mature by your last frost date. That last frost date is exactly where we will start our seed starting journey. This one is easy, I promise; you already know your grow zone from our previous post, so just Google “Last frost date + (your grow zone)” to find out when it’s safe to plant outdoors in your area, since this is the last date when all danger of a freeze has passed.

Next, go back to your list of everything you will be growing and open up Google. Search for each plant name + “when to plant”. For direct sown plants (that means we just put the seed directly into the soil outdoors) this will most often just be “after last frost” (unless it’s a cold hardy plant like spinach or kale which can usually be started a lot earlier) but for plants that need to be started indoors in order to mature before that last frost date, it will say something like “start indoors 8 weeks before last frost” Next to each line write down the planting timing. 

The benefit of using a spreadsheet when you are learning how to start seeds is that you can then sort the data in your list by the planting date instead of whatever order you had originally written them down in. This creates a planting schedule for starting plants from seed with just a click of a button. Otherwise you’re going to have to manually organize your list by planting date so you know what dates to do which tasks.

Should you use potting soil or seed starting soil?

Potting soil and seed starting soil are both designed to provide a suitable growing medium for plants, but they have some key differences based on the needs of plants at different stages of growth. Potting soil is a general-purpose mix that is formulated to support the growth of established plants, both indoors and outdoors. It often contains a blend of ingredients such as peat moss, perlite, vermiculite, pine bark, and sometimes added fertilizers. Potting soil may have added nutrients to support the nutritional needs of mature plants. Some formulations include slow-release fertilizers that provide nutrients over an extended period. Potting soil tends to have a coarser texture compared to seed starting soil. This coarser texture helps with drainage, aeration, and provides stability for larger plants.

Seed starting soil is specifically designed for germinating seeds. It typically consists of a lightweight and fine-textured blend, often containing ingredients like peat moss, vermiculite, and perlite. Seed starting soil is often sterile, which helps prevent damping off and other soil-borne diseases that can affect germinating seeds and young seedlings. Seed starting soil is formulated to retain moisture well, providing the consistent moisture levels necessary for seed germination. This helps seeds absorb water and initiate the germination process. Seed starting soil usually has minimal nutrients because seeds initially rely on the nutrients stored within them. As the seedlings grow and develop true leaves, additional nutrients may need to be provided through fertilization. Seed starting soil has a finer texture compared to potting soil. This fine texture allows seeds to make good contact with the soil, facilitating germination.

Use seed starting soil when germinating seeds in trays or small containers. The fine texture and sterile nature help create an ideal environment for germination. Once seedlings have developed a few sets of true leaves, you can transplant them into larger containers with potting soil, which provides the nutrients and structure needed for more mature plants.

What grow light should you use for starting seeds?

Don’t overcomplicate this. Grab some LED strip grow lights like these, and a couple of timers to turn them on automatically. Unless you are going to grow your plants indoors for their entire lifecycle and need them to flower/fruit without sunlight, you do not need to worry about the specific spectrum of light you’re using nearly as much.

How many hours of light do seedlings need?

You should set your grow light timer to give your seedlings 12-18 hours of light per day. I usually set mine for 16 hours.

What is germination?

Germination the development of a plant from a seed or spore after a period of dormancy. Most of the time, your seeds will germinate (or sprout) themselves simply by being activated through the process of hydration. So, you’ll put your seed into the soil at the recommended depth, cover with soil and keep damp, and this increase in the moisture content will trigger the germination of the seed. However, it’s important to check the germination requirements for any seed you haven’t grown before. Some, such as peppers, require a higher temperature in order to germinate successfully. Others like spinach and lettuce prefer a cooler temperature to germinate. Some seeds will just be duds and never germinate - that’s why you’ll often plant multiple seeds in one cell and thin them later, to hedge your bets. You can improve the rate of germination of certain plants like peas, beans, pumpkins and other winter squash by soaking them prior to planting. But, to be honest, since I have fatigue from my arthritis I don’t usually do this step and it’s usually just fine as long as you have quality seeds.

How do you prevent damping off?

Damping off is a common problem when starting seeds, and it is caused by various types of fungi that attack young seedlings, causing them to rot at the soil line. To prevent damping off, you can take several precautions. Start with a high-quality, sterile seed starting mix. Sterilized soil helps eliminate the presence of damping off-causing fungi. Ensure that the containers or seed trays you use are clean and have been properly washed or sterilized before planting. This reduces the chances of introducing harmful fungi. Overwatering can create a favorable environment for damping off fungi. Water the seedlings from the bottom to keep the surface of the soil dry. Use a tray underneath the pots and allow the soil to wick up water as needed. Adequate air circulation helps prevent the buildup of humidity around the seedlings. Use a fan on low speed or open windows to provide ventilation, especially if you are growing seedlings indoors. You should also aim to maintain a moderate humidity level. High humidity can contribute to the growth of damping off fungi. Proper ventilation and spacing between seedlings can help manage humidity levels.

By implementing these practices, you can reduce the risk of damping off and give your seedlings a healthy start. If you notice any signs of damping off, remove affected seedlings immediately to prevent the spread of the fungus.

Thinning seedlings

Thinning seedlings is an important step in the early stages of plant growth to ensure that the remaining seedlings have enough space, nutrients, and sunlight to develop into strong, healthy plants. Allow the seedlings to grow to a height where they have at least two sets of “true leaves”. True leaves are the leaves that follow the initial seed leaves (cotyledons) and have the characteristics of the plant species. Identify the strongest and healthiest seedlings. Look for seedlings with vigorous growth, a good color, and well-developed leaves. This does not necessarily mean the tallest - a short, stocky seedling is a better choice than a thin, leggy one. Instead of pulling out the excess seedlings, which can disturb the roots of neighboring plants, use clean scissors or small pruners to cut the unwanted seedlings at soil level. This ensures minimal disruption to the roots of the remaining seedlings. If you are thinning edible plants like lettuce or carrots, you can eat the thinned seedlings. Thinning can be a way to enjoy some early greens from your garden. Otherwise, just toss them in your compost.

Starting a GArden Checklist

1. Pick and order your seeds (don’t forget to check out this blog post if you get stuck)

2. Plan your garden layout (see this post for my tips)

3. Write down the planting dates for every plant on your list - both the seed starting date and the date to transplant

4. Gather your supplies; soil, seeds, cell containers to grow in or a soil blocker and trays, a trowel, a tarp to keep your work area clean, and your light source

5. Work down your list of seeds from the first planting date to the last

6. Presoak any seeds that require it for germination

7. Plant your seeds at the recommended depth

8. Keep the soil moist at all times - you can cover with any clear material to keep the environment damp until the seeds sprout

9. Build strength in your seedlings stems by gently running your hands across the surface of your plants daily, and keep a fan on to prevent damping off/mold

10. Harden off your seedlings by bringing them outdoors to a protected spot out of direct sunlight and wind (up against your house will do). Start with one hour for the first few days, then increase it by an hour every day until they are able to stay outdoors for all daylight hours

11. Transplant your mature seedlings into the garden when it is safe to do so, usually after your average last frost date

What else do you want to know about starting seeds indoors?

Garden Planning Part 2: Designing Your Garden Layout

The Cottage Peach is reader-supported. When you purchase through links on our site, we may earn an affiliate commission at no additional cost to you. All opinions are our own.

Planning your first garden can feel intimidating, but I want to show you a simple process that I use in my own garden design that breaks each step down into manageable pieces. This is a project I typically work on over the course of a few weekends here and there - it won’t necessarily take hours to complete, but it’s nice not to rush the process so you can modify and tweak things after giving yourself time to mull it over.

How to decide what to plant in your garden

I cover this in depth in my seed selection post which you can read by clicking here, but the key is to identify what foods your family eats the most of, that will grow well in your particular garden climate. This list is your starting point - all we have to do is assign each plant on the list to a particular spot in your garden layout based on a couple important factors, including what plants grow well together, what plants are natural “enemies”, the location of the sun on the land, and how many of each type of plant you will be growing. But I’ll cover all of that in a minute. First let's decide where your new garden should go.

How to decide where to put a garden

The best time to choose the location of your new garden bed is after about a year of careful observation, because this gives you a full year of seasons to notice and document the weather patterns (if an area tends to flood or dry out quickly for example) as well as the positioning of the sun throughout the spring, summer and fall. But if you’re reading this with the intention of beginning your new garden in a few days, weeks or months don’t fret! Some educated guesses can be made based on just a few days of observations. 

First, note the direction of the sun. In a perfect world a north-south orientation is best for low-growing crops, allowing direct sunlight to reach both sides of the bed. For taller crops such as pole beans, cucumbers and tomatoes an east-west orientation works best. The sun rises in the east and sets in the west, so just pay attention to your sunrise and sunset locations and you’ll be able to orient yourself based on that.

Next, throughout the day you’ll want to pay attention to shade and shadows. For instance, is there a tall treeline that means a certain area of the land does not get full sun throughout the day? If you have a choice to plant in full sun, you absolutely should - however, this doesn’t mean that your shady yard is inhospitable to planting. You’ll just need to modify your list of crops you plan to grow to include only those who thrive in lower light conditions.

Finally, notice the slope of the land. Unless your yard is perfectly flat, you probably have areas that will be easier to transform into a garden than others. We’ll talk about what to do if all the land available to you is on a slope next.

QUESTIONS TO ASK YOURSELF WHEN GARDEN PLANNING:

What is the purpose of the garden? Is it for aesthetics, food production, or a combination of both?

What is the climate and soil type of the area? What plants are suitable for this type of environment?

What is the size and shape of the garden space? How much sunlight does it receive? What is the orientation?

What type of plants do you want to grow? Do you prefer perennials or annuals? Do you want to grow edibles or ornamentals?

What is your budget for the garden? How much money do you have to spend on plants, materials, and tools?

How much time and effort are you willing to devote to the garden? Do you want a low-maintenance garden or are you willing to put in the work to maintain it?

What is the style of the garden? Do you want a formal or informal garden? Do you prefer a wild and natural look or a more structured appearance?

What is your level of gardening expertise? Are you a beginner or an experienced gardener?

Raised beds vs in-ground

Now that you’ve picked the location for your garden, it’s time to decide if you want to grow food in the ground or in raised beds. Each method has its pros and cons. I chose to switch to primarily all raised beds this year because fighting weeds in-ground and bending over the soil was not working for my back any more with my arthritis. The downside is that this means I have to pay for the beds themselves as well as the soil/compost to fill them. If you’re on a budget and don’t have the same physical limitations as I do, gardening in ground allows you to benefit from the pre-existing ecosystem within your soil including worms and beneficial bacteria and also means your plants won’t need to be watered as often.

If you’re gardening on a slope, I strongly recommend raised beds. With raised beds that sit on the earth you will be able to actually dig the base of the bed into the soil to make it even, effectively creating a level surface on which to plant. Just be mindful not to locate any plants that are sensitive to root rot at the lowest point of your slope since rainwater will collect most easily there.

How many vegetable plants do you need per person?

This is highly individual depending on your family and what you like to eat. You should definitely prioritize space in your garden for the foods you eat the most. For us, that means we grow a lot more broccoli, green beans and bell peppers than anything else. And no matter how much squash you THINK you will eat, one or two plants per household will probably yield more than you’ll ever be able to finish without sharing with your neighbors and friends. If you know you go through a lot of pesto, it’s a good idea to plant 20-30 basil plants. Refer to the chart below for some common amounts for popular vegetables.

What is companion planting?

Just as there are plants that do not grow well near each other because they compete for resources, there are many plants that get along quite well and actually offer benefits to their neighbors. You can harness this “companion planting” effect to grow more food in an even smaller space. You can also utilize taller, stronger plants to act as trellises for vining plants, prevent weeds by creating a thick overstory that will choke them out, planting certain herbs and flowers as a trap crop to repel pests, and benefit your neighboring plants with the addition of nitrogen fixing varieties such as snap peas or pull nutrients to higher levels for your shallow rooted plants with crops such as root vegetables.

Plants that grow well together:

There are countless companion plant combinations, but here are a few to get you started:

• For “trap crops” to keep pests away from your plants or repel them entirely, look into basil, dill, marigold, mint, nasturtium, sage and zinnias.

• Grow basil within 12 inches of tomatoes to increase your harvest. Basil also improves the flavor of lettuce.

• Growing chives near your carrots will improve their flavor. 

• Beans like to grow with Beets, carrots, chard, cabbage, corn, cucumbers, peas, and radishes.

• Strawberries like to grow with bush beans, chives, lettuce, onions, sage, spinach, and squash.

Plants you shouldn’t plant near each other:

Some plants compete with each other for resources or in the case of sunflowers for example, actively leech compounds into the soil that can cause harm to neighboring plants. Here are just a few common enemies in the garden.

Squash and potatoes

Tomatoes and corn

Zucchini and pumpkin

Asparagus and garlic

What is crop rotation?

Crop rotation means that you intentionally do not plant the same type of plant in the same exact spot each year, you “rotate” it to a new location. For example, nightshades such as tomatoes are prone to microbial diseases that live in the soil. For this reason it is recommended that you do not plant in the same spot for 4 years after the initial planting. Other nitrogen dependent crops such as corn suck so much fertilizer out of the soil that you want to give the earth a break before replanting the same variety in the same spot. This will be more important in your second and following years of gardening, so don’t worry about it too much right now!

how to design your garden layout

Now that you have your final list of plants, your garden location and type and an overall understanding of the basic concepts of companion planting and how many plants you will need, the hard work is done! All we are going to do now is effectively “fill in the blanks”.

All you will need is some paper and a pencil, but if you want to get really crafty with it, print out some graph paper and grab your highlighters too.

Start by drawing out the outline of the shape and size of the garden beds you will be creating. I like to do this to scale with graph paper where each square equals a square foot of the garden. You don’t need to get this precise with it - if you have a 4x4 area or raised garden bed, just draw a nice sized square on your blank paper and add your own grid lines or rows as you see fit.

Now go back to your plant list of everything you plan to grow this season. Assign each plant on the list a letter from A to Z. You should also write down the number of plants for each item on the list next to the plant name.

All you need to do now is just fill in your blank garden squares with the corresponding letter for each plant to assign it a location and the number of plants you will be planting in that square.

That’s really all there is to it! Once this is complete I like to go back and reorganize the plant list based on when I need to start the seeds and transplant into the ground after our last frost, but that’s a conversation for another day.

Need seeds? Tap here to visit my favorite seed company

Click here for part one: Choosing & Organizing Seeds

Click here for part two: Starting Seeds Indoors

Click here for part four: How to Use Companion Planting To Grow More Food