top of page
  • Mary

How to Start Garden Seeds Indoors

Updated: Mar 9

It's that time of year again! It's time to start seeds for this summer's garden! Whether you are new to gardening or seed starting, here is how to start your own seeds indoors!

Amish Paste Tomato Seedlings

Why start vegetable seeds indoors?

  • Starting vegetable seeds indoors is a great way to get a head start on the growing season your plants will already be several weeks old once it is time to plant in the spring.

  • Starting your own seeds allows you to have more variety in your garden, rather than the vague "red onion" or "yellow onion" transplants you would otherwise buy at the nursery, since you can search for several different varieties of a vegetable from seed online these days.

  • You know what has happened to your plants from the start: their growth patterns, pest issues, diseases, whether or not it has been grown organically or not.

  • Starting your own vegetables from seed is cheaper than buying transplants, as seed packets contain tens to hundreds of seeds for only a couple of dollars. One tomato transplant from my local big box store costs $5.48 currently, while a packet of Organic Roma Tomato seeds is $2.99 at True Leaf Market.

  • It is a fun activity for you and your kids!


  • Seed starting mix

  • A bowl

  • A large spoon for mixing

  • Water

  • Seeds

  • An oscillating fan

  • Seed tray warming mat (not completely necessary but will help things, like peppers, germinate)

  • Surge protector

  • Seed starting tray or empty yogurt cups with holes cut in the bottom. You can also purchase seed starting cups on Amazon. I like these because they are sturdy enough to use year after year, and large enough that you will not have to repot your plants once they outgrow the standard seed tray size.

  • Seed Cell holding tray - This is a tray that does not have holes in the bottom and holds the tray with your seeds. (Most of the time when you buy a seed starting kit, this is already included, but in case you don't have one, I like these because they are very sturdy.)

  • Humidity dome - This also should be included in your seed starting kit, but if you do not have one then you can use several layers of cling wrap. This is really only required for germination.

  • Lights. I can do an entire separate post about grow lights and their requirements, but the short version is that you are looking for something that is between 5500-6500k, with at least 3000-5000 lumens per bulb. For every square foot of growing space you will need at least 3000 lumens, but 4000 or 5000 lumens is better. For example, if your seedlings take up 4 square feet of growing space, you will need between 12000 and 20000 lumens total, which you will get by buying several lights to add up to that amount of lumens. I have done hours and hours of research on lights for seed starting, and these are the ones I ended up getting. They are 4ft, 6500k Ultra High Output (Non-Dimmable) Daylight Deluxe shop lights, which offers 8,000 lumens per fixture. I have two fixtures for my 4 square feet of growing space. I like these lights because you can just unbox them and plug them in and they are ready to go! (You do not need to buy these exact lights as long as the lights you find are between 5500-6500k (6500k being daylight, which is preferred) and 3000-5000 lumens per bulb you should be set.)

NOTE: If you are considering starting your seeds indoors but do not have proper lights with the proper requirements, you should not start your seeds indoors. Seedlings are not like fully grown plants; they require A LOT of light. While you CAN put your seed trays in a south facing window for light, they will not get the proper start they need and will grow leggy and weak. When you go to transplant them, they are more susceptible to transplant shock, and if they happen to survive they will produce very little to possibly not at all. It will be a huge waste of time and resources. If you are unable to purchase good lights, I recommend buying healthy transplants at your local nursery to avoid disappointment later. You do not want to waste time!

How To Start Seeds Indoors

Step 1 - Decide what you want to grow.

Step 2 - Gather your seeds. Some of my favorite places to get seeds from are:

Here are some of the things I am growing this year:

You can also pick up seeds at your local nursery and big box stores. I like shopping for seeds online because there is often a higher selection of seeds, and you can read about and choose varieties that are disease and pest resistant. Many big box store seeds can be cheap and are not resistant to diseases and pests that may be a problem in your area.

Step 3 - Look up your average last frost date. This is a good resource; all you have to do is enter your zip code. Your average last frost date is the last day it is predicted to frost in your area. Knowing your average last frost date will help you determine when to start your seeds.

This date changes each year.

Planting the day after the average last frost date is the earliest you can transplant or direct sow most seeds. You can absolutely (and I highly recommend to) wait a few weeks after the average last frost date to plant your seedlings to completely avoid any surprise frosts that might happen (which happens a lot, in my experience).

Step 4 - Read each seed packet and find out when your seeds need to be started. Some seeds, like peppers, need to be started 10-12 weeks before your average last frost date, while other things, like cherry tomatoes, need to be started 4-6 weeks before your average last frost date. The seed packet will also tell you what you can directly sow into your garden without starting indoors, and what the growing requirements are (how deep to sow, spacing, etc.) for a particular seed.

For example, I want to start tomatoes and peppers inside. According to my seed packets, my tomatoes need to be started 6 weeks before my average last frost date, and my peppers need to be started 8-10 weeks before my average last frost date. My average last frost date is April 5, so I will look at my calendar and count back 8 -10 weeks for my peppers and 6 weeks for my tomatoes, and that is when I can start them inside.

PRO TIP: First, my recommendation is to count two weeks after your average last frost date and make that day your new "last frost date" in order to avoid any surprise frosts. Consider it a buffer.

Second, if you wish to plant all of your seeds at once despite them having different "start indoors" dates, take the longest start ahead date (which will usually be 8-10 weeks, so we will average that out at 9 weeks) and count back 9 weeks from your new "last frost date". By doing this, you can plant all of your seedlings at once, and when it is time to transplant the plants that require less time to be ready for transplant (your 4-6 week plants), it will already be at your area projected last frost date. (I wish that makes sense! The point is that you only have to take out all of your seed starting supplies once., and you will transplant seedlings into your garden as they become ready.)

Step 5 - Gather your supplies and set up your lights. The easiest way to set up your lights is to hang them from a wire shelf. If this is not an option, you will have to figure out a set up that works in your space. There are several videos on YouTube for different ways to set up a grow station. It is preferred that your lights are somewhat adjustable as you will want your lights about 1.5-2 inches away from your seedlings at germination, and about 3 inches away from them as they grow. This is also a good time to lay out your seed warming mat. Connect everything to the surge protector and plug that into the wall.

Step 6 - Start your seeds! You know which seeds you need to start, you have your supplies, you've waited for the right time, and now you are ready to start your seeds! Here's what you do.

1. Fill your big bowl with seed starting mix.

2. Add water until the soil feels like your towel after you have taken a shower. It should be damp but not dripping wet. The soil should at least hold together if you squeeze it.

3. Scoop soil into your seed tray and tamp it down gently; enough to where there are no air pockets. Leave about 1/4 inch of room at the top. Your seed tray should have two parts: the cell tray which will have holes in each cell, and a tray that holds the cell tray. This tray will not have holes. If you have individual cups that you put holes in yourself, place these cups into a hole-less tray.

4. Make your labels and put them in your seed trays. You can do this by row or make individual labels for each cell.

5. Place 2-3 seeds into each cell.

6. Place more seed starting mix on top of your seeds, tamp it down, and water it with a few tablespoons of water, just so that all of the soil settles in.

7. Cover your trays with a humidity dome or several layers of cling wrap and place them under your grow lights. You do not have to turn your lights on yet, unless light is required for germination. Check your seedlings for any signs of greenery, and once you see little plants poking through the soil, immediately turn your lights on. It is important that you turn the lights on as soon as possible to prevent leggy-ness in your seedlings. (Leggy-ness happens when your seeds are not getting enough light, so they continue to stretch and grow tall in search for that light. They think they are still burrowing through the soil!)

8. Once seedlings emerge, it is good to have an oscilating fan to blow air on them to encourage strength. This mimics wind, so that when you transplant them into the garden in the future, they will be strong enough to survive.

9. If soil on top of the tray gets dry add a tablespoon or two of water to each cell. Once seedlings are an inch or so tall, start bottom watering. Pour water into the bottom tray until it is a couple of centimeters deep. After 10-15 minutes, remove any excess water that was not wicked up by the plants. The soil should be slightly damp. It is good to wait for the soil to dry out a bit between waterings, as this encourages root growth downward in search of water. However, do not let the soil dry out completely between waterings.

(Be on the lookout for a future post about fertilizing and caring for your seedlings as they grow.)

9. Now, you wait! Go have yourself some scotch and relax, because before you know it, you will have a bunch of seed babies that you will need to plant in the ground! Consider it the calm before the storm!

One of the first little seedlings to pop up this year: Megaton Cabbage. In just a few months, this tiny little seedling will produce a cabbage head that is 15-20 lbs!

If you are planning on starting your own seeds this year, let me know what you are starting! I started mine last week, and have little cabbage, onion, pepper, flower, and tomato babies already!

I will keep you updated as my seedlings grow, and let you know what to do for each phase of the growing and gardening process along the way!

See you next Monday!



Related Posts

See All
bottom of page