Indoor Seed Starting 101
A tray of mesclun microgreens on display at Gardener’s Supply in Williston, Vermont.
A Beginner's Guide to Indoor Seed Starting
This seed starting guide, originally presented at the Waterbury Public Library in April 2025, explores the basics of starting plants from seeds indoors. Whether you have a green thumb or not, this guide will help you get started on your gardening journey. Scroll through the slides above or read the outline below.
Why Start Your Own Plants from Seeds?
“To own a bit of ground, to scratch it with a hoe, to plant seeds and watch the renewal of life - this is the most commonest delight of the race, the most satisfactory thing a (person) can do.” -Charles Dudley Warner
Growing plants from seeds offers numerous benefits, from saving money to harvesting earlier. It can also serve as a fun, therapeutic hobby.
Earlier Harvests:
put fresh food on the table sooner
sooner you can pick, greater yield
Greater Variety:
choose the exact plants and varieties you want to grow
greenhouses and nurseries offer just a tiny fraction of all the possibilities
grow more disease resistant varieties
grow more heirloom or gourmet varieties
Stronger Seedlings:
do all the right things at the right time, you'll have the best starts
well-developed roots
grown in good soil without chemicals
organic seeds, organic growing mix, organic fertilizers
Healthier Seedlings:
minimize chance of introducing soil-borne disease to your garden
Cost Saving:
1 packet costs ~$3-$5 and you get between 25-250 seeds
nursery plants cost on average $6-$8 per pot/pack.
still need to factor in the price of materials (mix) and supplies (lights and mats)
Satisfaction:
ownership and pride associated with the loving care of growing your own plants
watching it start as a tiny seed, sprout, and then grow into a large, luscious productive food crop
Enjoyment:
cure for the winter blues
fun hobby
Therapeutic:
research shows working with plants has a positive impact on our mental and physical health
Seed Facts
Seeds are alive!
seeds contain living plants, but only the most rudimentary parts
they carry on respiration: they absorb oxygen and give off carbon dioxide
they absorb water from the air
Seeds are a ripened fertilized ovule containing an embryonic plant and a supply of stored food surrounded by a seed coat. Seeds possess enough food energy to carry them through dormancy and into their early days as seedlings. If you soak a bean seed in water for a few hours, the hard outer coat will slip off. The bean that you now see is composted of cotyledons, the “meat” of the seed. All seeds have cotyledons, the "meat" of the seed that stores all the food it needs to carry them through dormancy and into early days as seedling.
Selecting Seeds
Some plants are more forgiving than others, making them ideal for beginners. Some plants, especially root veggies, do better directly sown in the garden.
Consider your space and growing conditions
Choose plants that match your experience level
Popular choices for beginners:
Leafy greens: lettuce, arugula, kale
Herbs: chives, oregano, sage
Flowers: sunflowers, cosmos, zinnias, marigolds
Where to Get Seeds
Seeds are widely available at physical retailers like local nurseries and garden centers and online direct from seed companies. Some communities have seed libraries and host seed swapping events. Learning to save your own seed is an even more cost effective and satisfying method. When purchasing, always buy a reputable brand. Avoid GMO. Try to find organic.
Nurseries & Garden Centers
Food Shelves
Seed Libraries
Friends & Family
Seed Swaps
Hardware Stores
Grocery Stores
Seed Companies
Save Your Own!
Must-Have Supplies and Resources
To get started, you'll need a few essential gardening supplies and resources.
Growing medium
Water source
Pots or containers
Heat source
Light source
Air circulation
Choose Your Seed Starting Mix
Choose a mix that will nurture your seeds through germination and seedling stages. Seeds don't need rich soil. Physical conditions of their surroundings are more important for germination: temperature, moisture, air, and light. Don't use plain garden soil, it will pack and crust when used in shallow containers. The mix should be:
Sterile
Weed seed free
Disease & fungus free
Absorbent
Able to drain quickly
Fine textured
Organic & sustainable
Noncrusting
*Avoid peat moss which is not a sustainable soil amendment
Choose Your Containers
You can repurpose food and beverages containers (at least 2" deep) found around your house like:
plastic food containers: yogurt, cottage cheese
Beverage cartons & plastic gallon jugs
Aluminum disposable loaf pans
You can purchase new containers from garden stores specific for seed starting like:
Multi-cell plastic flat inserts & plastic flats/trays
Biodegradable CowPots & EcoGrow Pots
Soil blocker
Clay pots
*Avoid peat pots
Make Your Own Containers!
Get creative with materials and supplies you have around your home for an even more sustainable, cost-effective approach.
Newspaper pots
Wooden Flats
Paper snail rolls
Choose Your Light Source
Plants absorb energy from light and use that energy to make food they can store. It is critical to provide seedlings with sufficient light to grow and thrive. Seedlings should get 16 hours of light a day.
Natural sunlight
choose a south facing window
not sufficient for most vegetable plants
Fluorescent lights
duplicate the color spectrum of sunlight
need a double row of tubes to give enough light for a tray up to 16 inches wide
need to put the light as close to the plants as possible and move it up as the plants grow
LED grow lights
more efficient than fluorescent bulbs
produce little heat
combination of colors more closely duplicates the light plants need to grow
many tiny bulbs which produce a single color of light
need to be further away from the plants to prevent scorching
cost more than fluorescent but last twice as long and use less electricity
Ideal Temperatures
For germination, most seeds require soil temperatures of:
75 degrees to 90 degrees F
Heat mats use less power than heating the whole room
OR safely place pots on a high shelf near a furnace, water heater, wood stove or heat register
After germination, seedlings will grow best when the air temperatures are:
70 degrees to 75 degrees F during the day
55 degrees to 65 degrees F at night
Set Up Your Indoor Growing Space
Arrange your space based on:
How much space you have to dedicate to seedlings as they grow
The type of light source and distance from light
Heat and air circulation sources
Seed Starting Timetable
The date you start seeds depends on:
Plant variety
Indoor location & lighting
Average spring frost-free date in your area (May 18th for Waterbury, Vermont)
The right time to start your seeds indoors varies significantly, ranging anywhere from 2–16 weeks prior to transplanting outside.
Check your frost-free date at Farmer’s Almanac: https://www.almanac.com/gardening/frostdate
Sowing Checklist
Now that you have all of your supplies and know when to start seeds, it’s time to sow!
Gather your equipment
Prepare your workspace
Review your seed packets
Prepare your containers
Prepare your seeds
Plant the seeds
Cover the seeds
Label the container
Cover the container
Set the containers in a warm place
What Seedlings Need
Plant sprouts are like babies, they must have their needs met to thrive. Check on them and nurture them regularly!
Light & Heat
Moisture
Space
Air Circulation
Transplanting
AKA “potting up”
Why transplant?
Stimulation of feeder roots
Room to grow
Richer soil
Easier selection and evaluation
Best time to pot up seedlings is when they have their first “true leaves”.
How to transplant:
Prepare the container
Prick out seedlings
Replant seedlings
Watch your seedlings
Hardening Off
You’ve coddled your plants indoors now it’s time to toughen them up for the “real world”. Before planting out, seedlings must be gradually introduced to outdoor elements:
Sunlight
Wind
Cold
How to harden off: Two weeks before your planting out date, move your seedlings outdoors to an area protected from strong wind. Leave them out for 1-2 hours on Day 1, 3-4 hours on Day 2, and so on until they spend the whole day and night outside.
Pro Tip: Help prevent transplant shock by mixing fish emulsion fertilizer into the water you use when planting out
Troubleshooting Common Issues
Even with the best care, your seedlings may encounter some problems.
Leggy stems
reaching for light, move light closer
temp too high
Leaf curl or yellowing of lower leaves
over fertilization
Mold
poor drainage
lack of air circulation
Insect damage
Bud drop
air too dry
Leaf discoloration
Root discoloration
Damping off (fungus)
stem withers at base
Failure to sprout
Resources
To aid you in your seed starting and gardening journey
Gardening Advice
Ask Rachel, your personal garden coach: www.goldenroddesignvt.com/contact
Ask a UVM Extension Master Gardener: go.uvm.edu/gardenquestion
Books
The New Seed Starters Handbook by Nancy Bubel with Jean Nick, Rodale, 2018
Seeds & Supplies
Seed Library at Waterbury Public Library
Evergreen Gardens, 15 Cabin Ln, Waterbury Center, VT 05677
Let’s Get Planting!
Remember, indoor seed starting is a rewarding and enjoyable hobby. With a little patience and care, you can create a beautiful garden with plants you grew from seed!
Happy Gardening!
