University of Maryland Extension

Seed Starting by Allegany County Master Gardener Brenda Gross

Allegany County Master Gardener Brenda Gross
tray of seedlings

Indoor Seed Starting

By Brenda Gross, Allegany County Master Gardener

It is the time of year to start seeds indoors to grow our favorite plants to transplant later outside in our garden. It may be our favorite vegetables or flowers we can’t buy locally, or maybe we just want the satisfaction of growing them ourselves.

First, decide what seeds you want to purchase. Consider the number of seeds in the packet; how many plants do you want to grow? Check on the planting zone for when it is safe to plant outside. The package will tell you many weeks before that frost date to start the seeds indoors.

There are several seed starting videos available on the web site that will be helpful to watch.

It is best to start seeds in small individual containers. Plant a single seedling per container to avoid the seedlings roots from growing into each other. The containers should have drainage holes in the bottom. There are plastic “cell packs” with multiple “cells” for individual seedlings. These are generally reusable if they are cleaned and disinfected each year.  Some of these cell packs have a clear plastic dome that can be used to retain moisture and warmth when first starting seeds. There are fiber pots made of peat, shredded wood, or cow manure. Pots can be made from folded newspaper, see HGIC’s a demonstration on YouTube:  The fiber or paper pots will break down in the soil when planted in the garden.

Soil-less seed starting mixtures are recommended for starting seeds. These mixes are sterile, lightweight, porous and free of weeds. Fill the planting containers with the potting mix and water it before planting the seeds.

Plant the seeds according to the package directions.  Be sure to label your flats or pots!  Use plastic sticks and mark with a permanent marker to label. Some seeds need light for germination, some need darkness.

Most seeds need consistently warm soil to germinate. Cool soil temperatures can lead to seedling death. Excess heat can dry out the potting mix, causing seedling death. Windowsills are not the best location due to variations in cold, heat and light. A location with adequate space, air temperatures above 60°F are adequate if bottom heat is provided. Seeds of most plants started indoors germinate sooner and produce healthier roots when the potting soil is warm. Electric heating mats specifically for seed starting are available.

It is better to grow seedlings under fluorescent lights than to rely on natural light. Two “cool” white fluorescent tubes provide adequate light. Keep the lights 1to2 inches above the tops of the seedlings. Plants need 12 to 16 hours of light daily. Use chains to hang the lights so that the height can be adjusted as the seedlings grow.

Keep the potting mix moist while the seeds are germinating. Add water to the tray to allow moisture to be drawn up into the mix. No standing water! Seedlings don’t need fertilizer until they have several sets of true leaves. Those grown in a soil-less mix may benefit from water soluble fertilizer at ¼ strength once a week.

Plants started indoors will need to be “hardened off” before planting them outdoors. Start by putting them outside in the shade for a few hours in the afternoon. Each day, leave them out a little longer, gradually exposing them to direct sunlight. By the end of two weeks the transplants the seedlings can stay outside until they are planted in the ground.


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