The Ultimate Guide to Seed Starting for Beginners: Seed Starting 101

It is finally time to start thinking about starting your seeds for the coming year's garden. There are a few things to pay close attention to as you start planning and planting for your garden:

What is my hardiness zone?

The USDA hardiness zones are based on average coldest temperature in a location. As the climate has shifted over the last 20 years, the hardiness zones have been updated and were just recently changed. You will want to be familiar with your hardiness zone as it is often referred to on seed packets and on plant tags. You can easily look up your zone here. Once at the site, input your zip code at the top of the screen; this will give you the zone you are in. My zone is listed as 7a, however I know that this is based on zip code and may not be entirely accurate. Because I am located on the foothills or bench of a mountain, I know that my specific climate is more like a 6b - meaning the temperature where I am located, or in my microclimate, is slightly cooler than the general location.

When should I start my seeds?

Timing for starting seeds depends on the average last frost date for your area. For example, mine is May 11th. This means that I likely will not have temperatures lower that 32F after that date. Temperatures can vary from year to year, so placing plants into the garden may be earlier or later than the average date.

Plants are categorized into groups based on hardiness, or the lowest temperatures they can withstand.

• Cold hardy vegetables can be placed in the garden about a month before the last frost date (for me this is April 11th). These vegetables include peas, brassicas (broccoli, cauliflower, cabbage, kale, and related plants), onions and leeks, radish, turnip, mustard greens, spinach, and fava beans.

• Semi-hardy vegetables include beets, carrots, endive, lettuce, parsley, potato, and Swiss chard and can be planted out two weeks prior to the last frost date (around April 28th at my location).

• Tender vegetables are those that cannot withstand freezing temperatures and should be planted on or after the last frost date (May 11th). These include celery, cucumber, beans, squash, and corn.

• Very tender vegetables are those that must be protected from temperatures below 50F and are planted two weeks after the last frost date (May 25th at my site) or they can be planted earlier with season extension such as Wall O' Water or row covers. These include melons, eggplants, peppers, tomatoes, and winter squash.

Directions dictating the number of weeks to start plants prior to the transplant date are found on the seed packet. For example eucalyptus should be started 10-12 weeks prior to the last frost (May 11th for my area), giving me a sowing date of February 17th. You simply need to look at the plant hardiness category (cold hardy, semi-hardy, tender, very tender) and the expected date of transplant and count backward the number of weeks to calculate your sowing dates.

What equipment is needed to be successful?

Basic equipment needed to start seeds successfully includes:

• Clean, durable containers. Whatever container you choose to start seeds in, make sure it is clean by rinsing with a 10% bleach solution. Soil born pathogens that can cause problems such as damping off and root rot can lurk in retained soil and in dirty containers. You can choose to start seeds using container-free soil blocks, and we will discuss this at length at a different time. When starting seeds, I like to start in a four or six cell pony pack and then as plants grow, I will bump up (or pot up) my seedlings to a 4-inch container to establish larger roots and plants.

• Seed starting soil or growing medium. This is actually a soil-less medium, meaning that it is composed of materials like coconut coir, peat, perlite, and vermiculite and no actual soil. The mix should be light, composed of small particles (no big hunks of wood), and should hold moisture well. I like to moisten my growing medium before sowing as it can be difficult to fully wet without mixing and agitation.

• Heat mat. A heat mat is exceptionally helpful to get seeds to germinate at an even rate. Most seed packets will suggest germination temperatures, usually somewhere between 65-75F. You can get a thermostat that connects to your heat mat to help set the temperature at the correct degree. I have found that 70F is a good all-around temperature for multiple seeds germinating on the same mat. A heat mat isn't entirely necessary if you have a warm environment, but it will even out germination and help your plants be more uniform. Once your seeds have sprouted, take them off the heat mat. Prolonged heat can cause leggy growth and can promote disease growth.

• Full-spectrum lights. The biggest question I get about seed starting is "is the light from a window enough to start seeds from?" The answer is "yes, but..." If you want strong, well-formed seedlings, you should utilize lights. Seeds germinated in a window will sprout and grow, but your seedlings are likely to be leggy and elongated (what we term as etiolation), giving you plants that can struggle to produce a thick, straight stalk and stand on their own, even when mature. You do not need "grow lights" instead you need a full spectrum bulb that provides light in wavelengths from red to blue. I set my lights to a timer so that they are on for 12 hours during the day and automatically turn off - one less thing for me to remember. Lights should be placed as close to the plants as possible - ideally an inch or two above. You should have a way to raise and lower the light to match plant height and I have found a simple metal chain that I can shorten and lengthen with s-hooks works for me.

• Viable seeds. Germination of seeds declines with age, so I recommend that you plant new seeds as often as possible. Older seeds can be used, but you may need to plant seeds several per cell to ensure germination. Make sure to source seeds from reputable companies with good customer service.

Sowing or planting

Sowing seeds has it's own caveats. There are sometimes odd instructions on the back of the packets with words like scarify or stratify. Learning a few tips and tricks will help you carry out these sometimes cryptic tasks.

• Depth. Sowing depth is relative to seed size. Sow seeds at twice the depth of the width of the seed. If you are dealing with a very small seed like snapdragon or feverfew, the seeds will be planted on top of the soil versus a squash seed that will need to be planted an inch into the soil. Seed packets will often supply this information, so be sure to read.

• Light needed to germinate. Some seeds cannot initiate the germination process if they are covered with soil. These seeds must be surface sown. Surface sown seeds are often small and can easily be buried under soil when watered. You can bottom water by placing them in a solid tray without drainage holes and filling with water. Once the growing medium has absorbed the water, you will want to drain away any excess. You can also use a spray bottle to gently mist the top of the soil where the seeds are. Humidity domes or plastic wrap can help hold in moisture while seeds germinate. Occasionally instructions will say to place a layer of perlite or vermiculite on top of the seeds to help hold moisture. Make sure the layer is think and that light can still penetrate to the seeds.

• Stratification. This is a term used to describe climactic conditions that a seed must be exposed to before germination will begin. Most often these seeds require exposure to moisture and cool temperatures for several weeks. To stratify: moisten a paper towel, place your seeds on it, fold it up and secure in a zip top plastic bag. This bag should be labeled and placed in a refrigerator for the number of weeks recommended on the seed packet. Once you reach the required time, you can plant the seeds into containers and place on a heat mat and under lights (if required). Seeds will then germinate and the growing process will begin. Seeds that require stratification are often perennials such as echinacea, rudbeckia, chamomile, lavender, hops, solidago, and many more.

• Scarification. This is a process that mimics the seed being passed through an animal's acidic digestive tract or being hit with the hooves of traveling animals. This process breaks open the outer layer or exocarp of the seed so that water can move in, imbibing the seed contents and starting the growing process. I usually use a fine grit sandpaper for this task, although it can also be accomplished with fingernail clippers on flat seeds such as gourds. I carefully sand through the outermost layers of the seed so that water can penetrate. Once this is done, plant the seed as outlined in the instructions.

Watering

Once seeds have been planted it is important to keep the environment moist to ensure germination. Humidity domes can reduce watering frequency. I check my seeds daily, looking for any signs of drying or needing water. Bottom watering is ideal and can be accomplished by filling a solid tray with water and placing your containers in it long enough to absorb the needed moisture. Remove containers once the growing medium is wet and allow the medium to drain away any excess water.

Do my seedlings need fertilizer?

Seedlings do not need fertilizer until they develop true leaves. These are the leaves that look like the mature plant - usually the second set of leaves that develop. The first set of leaves are termed cotyledons and are remnants of the inside of the seed. They can carry out photosynthesis to some degree, but have stores of carbohydrates and nutrients in them to help the plant get growing. Once true leaves form, the plant will start to fully photosynthesize and uptake nutrients from the roots. At this point you can add a very light water soluble fertilizer every few weeks. I usually begin fertilizing once I have two sets of true leaves or plants look like they need a little boost. Fertilize at half the recommended rate for seedlings, as they are very tender and can easily burn from the salts in fertilizer.

Once seedlings sprout

Remove the heat mat and humidity dome once seedlings sprout. Make sure that the light is placed an inch or two above the seedlings and move it upward as they grow. Water as needed and the top of the soil starts to dry out. Keep a close eye on your seedlings as they do not have extensive root systems and can wilt quickly. Make sure that they are well drained and that they aren't sitting in excess water or being watered too often as this increases the incidence of root rots and disease. Once containers look like they are becoming too small and 50-75% of the soil is filled with roots, bump seedlings up into larger containers. I usually go from a pony pack size to a 4-inch container and this gives me plenty of room to grow until it is time to plant out into the garden.

Hardening off

Hardening off transplants is essential and without this process, you are likely to kill your tender, young plants. Two weeks before transplanting, move your seeds either outdoors or to a much cooler and brighter environment. This should be a gradual transition meaning that you place seedlings outdoors for and hour and then increase the time they spend outdoors each day. This gradual transition will help to toughen leaves to withstand both cold temperatures and the strength of the sun's radiation. At the end of two weeks, plants should be able to withstand day and nighttime temperatures and conditions. If you are at all concerned or it looks like temperatures are going to drop excessively, cover your plants with inverted pots or blankets to keep them from freezing or shocking. Utilize season extension such as cold frames or row covers whenever possible to minimize plant stress.

Still have questions? Leave a comment. Happy gardening!