“I would love advice on saving seeds off of heirloom bell peppers.” Question from Shelby of Greenleaf, Idaho
You are in luck! Peppers are some of the easiest seeds to save because they are dry, rather than fleshy, fruits with open interiors. What is important is waiting until the fruits are ripe to harvest the seeds. Green peppers have immature seeds that will not germinate. Once the fruits are fully colored and ripe, the seeds will be ripe.
Collect the seeds, place them in a labeled packet, and store them in a cool dry place through winter. I generally start my peppers in late winter or spring, at least eight weeks before the last frost date.
Please watch the video below for tips about how to grow peppers organically!
Spring will be here before you know it, and this means it is time to buy this year’s perennials, whether old favorites or new ones you haven’t tried before. The problem is how much they cost. To plant a modest new bed of perennials, you can expect to pay over $100 for just eight to ten plants. Growing them from seed is much more cost-effective if you know what to grow and how to grow them.
As a lifelong gardener and former perennial nursery manager, I am sensitive to the cost of these garden staples. Perennial plants seem to get more expensive year after year. For example, I planned to buy several butterfly weeds (Asclepias tuberosa) this season to help the struggling Monarch butterflies. But, even small pots are $8 to $10 per plant or more. Most designers recommend planting garden flowers in groups of three or more, so that is a minimum of $30.00 for just three plants, and more is always better. That is a lot of money! In turn, butterfly weed seeds are usually no more than $3.50 for a packet of 50 seeds. Wouldn’t it be nicer if you could grow them from seed and save a fortune? Here’s how to do it.
Perennial Seed-Starting Materials
There are a few essentials that home growers need if they are not fortunate enough to own their own greenhouse, conservatory, or sunroom. The items are low-cost and most can be used year after year. I do not recommend windowsill seed starting if you intend to grow seedlings to planting-sized plants because even south-facing windows don’t provide enough uniform light to keep seedlings from stretching and becoming spindly. Fancy seed starting racks or systems can be purchased, but I have always found the following materials to work just fine for all of my seed starting needs, and I’ve been doing this for nearly 50 years.
Then you will need special seed starter trays. It is a small investment, but quality starter trays can be washed and reused for many years. I recommend Delxo Seed Starting Kits with trays that have 48 individual planting cells for lots of seedlings and a watertight base tray. The kits also come with plastic covers with air vents at the top to control temperature and humidity, plus small tools, to help plant the seeds, and remove the seedlings. The kit even comes with its own labels, though I always like to have extra wooden planting labels because they are always handy.
If you reuse your trays or labels from year to year, be sure to scrub them out with hot water, dish soap, and a little bleach before using them again. Remember to rinse them well to remove any bleach residue.
Seed Starting Mix, Fertilizer, and Waterer
And lastly, you need a special seed starting mix, such as Black Gold Seedling Mix, which is extra fine for small or large seeds and lacks added fertilizer or salts, which can inhibit sprouting in some seeds. Our OMRI Listed Black Gold Seedling Mix also has an added organic wetting agent, to keep it from repelling water when dry, and it contains RESiLIENCE, a special silicon additive that is believed to promote better root growth, denser branching, and faster recovery should you forget to water.
Once seedlings start to put out their true leaves, you can start fertilizing them. I always choose quality, all-purpose, water-soluble fertilizer, such as Proven Winners Water Soluble Plant Food. Seedlings need gently water from the top in addition to bottom watering. Misters or small watering cans are very useful for seed starting.
Before addressing what to grow, there are two sources for perennial seeds that I always use and highly recommend. The first is Park Seed (visit their website to request a catalog). They have a huge collection of seeds, and I have been buying from them since the early 1970s. Their seeds are always fresh, well packaged, and germinate well. The other perennial source I adore is Select Seeds. They are the only company I know of that has heirloom flower seeds, some going back to the 1600s. Their packets are filled with many seeds, and they always do well for me. Swallowtail Seeds has lots of varieties and comes highly recommended. Finally, my oldest daughter grows lots of native perennials and has recommended Prairie Moon Nursery to me on many occasions for their quality seeds. You might also try your hand at seed collecting from year to year, if you feel adventurous.
Perennial Seed-Starting Steps
Read Your Seed Packets
Start by reading your seed packets from cover to cover. Some perennial seeds can be planted with no preparation, but some need to be nicked or chilled in the refrigerator for several weeks to properly germinate. Those that I highlight below are not challenging to start, but It is good to know that some seeds need a little more attention.
Gather Your Materials and Prepare Seedling Area
Next, gather all of your materials. Make sure to hang your lights and prepare your growing area. I like to put down a plastic table cloth to protect any tables from leakage and for easy cleaning. Fill up your watering cans and misters, and get going.
Prepare Your Planting Trays
Wash your hands before starting, to avoid any contamination. Put the seedling mix into a bowl, and wet it until uniformly moist. Fill the cells in the trays with the moistened seed starting mix, and be sure to leave a little space at the top for large-seeded perennials. (After reading the back of your seed packets, you will know if the seeds need to be covered or not.) I like to determine how big seeds are before I start planting. Some seeds are dust-like (Begonia seeds), while others are very large (perennial sunflower seeds), so some are simply sprinkled on the soil surface while others must be covered.
Sow Your Seeds
I like to sow two seeds per cell to make sure I get at least one seeding per cell. When working with small to medium seeds, I sprinkle two into the cell, making sure that they are separated, and then gently press the seeds down into the mix. (If both seedlings pop up, I either remove the weakest seedling after the seedlings have grown a bit, or I gently move one of the seedlings to an empty cell.)
Label, Water, Cover
Label the cells, either as groups or individually, marking each different flower you are growing and the date planted. Mist the seeds, but make sure that the soil is moist, not saturated. Saturated soil will cause seeds and seedlings to rot before they get a chance to grow. Put the cover on the tray, and lower the lights as close to the tray as possible. The plastic cover keeps the mix from getting dry, but aeration is also important. Sometimes I lift the cover for several hours in the day to let things dry out a little.
Once the seedlings have all popped up, remove the lid entirely. Too much moisture will cause damping off, or seedling rot. When you have removed the lid, keep the grow lights just inches above the small plants. This will encourage the densest growth and keep plants from becoming leggy. This is also the time to start feeding the seedlings weekly with a 1/2 strength solution of fertilizer. Fast-growing perennials may need to be upgraded into larger, 4-inch pots, some won’t. They will also require a little more water, so make sure you don’t let them get dry. Lightly moist soil is recommended. When your seedling is large enough to plant, usually 5-8 inches, and the spring weather allows, it is time to harden them off and get them planted.
Harden Seedlings Off
When the threat of frost has passed, it’s time to move the seedlings outdoors for hardening off, which reduces shock and helps perennials acclimate them to a sunny, outdoor environment. Start by bringing the trays outside, starting with a couple of hours, and increasing it until they are well adapted to the light, wind, and temperatures of the outdoors. After a week or so of hardening off, you can plant your perennials in the garden!
New plants always grow best in a prepared bed (OMRI Listed®Black Gold® Garden Compost Blend will increase organic matter and drainage) or container filled with quality potting soil. Be sure to plant your seedlings in locations with the right sun and soil for their needs.
At planting time, be careful with your little perennials. When removing one from a cell never pull it out from the top. Instead, tip the tray partway over and push up from the bottom to release the roots. A butter knife can also be used to lift small plants from cells or loosen perennials from a 4-inch pot. fertilize time-released fertilizer for easy summer feeding.
What Perennials to Grow from Seed
There are lots of easy perennials that will bloom in the first year from seed. I have grown and enjoyed ‘Gay Butterflies’ butterfly weed, black-eyed Susans (Rudbeckia spp.), phlox, catmint (Nepeta spp.), asters (Symphyotrichum spp.), perennial geraniums, salvias, blanket flower (Gaillardia x grandiflora), and many other wonderful, easy perennials from seed. Over the years, they have brought me much joy and saved me lots of money! Here are growing details for a few of these.
Purple Coneflower (Echinaceapurpurea)
First, I recommend growing varieties of coneflower (Echinacea spp), which is one of the easiest perennials to grow from seed. I especially recommend the AAS award-winners, ‘Pow Wow Wildberry‘, which has large, bright pink flowers, and ‘Cheyenne Spirit‘ with its mixed coneflowers in lovely sunset colors. Both will sprout in no time and bloom in the first summer. Bees and butterflies will cover the blooms. (Click here to see more varieties.)
Seed Starting: Cover seeds lightly with seed starter, and keep them lightly moist. average room temperatures between 65º and 70º F encourage good germination. Seeds should sprout within three weeks.
Blanket Flower (Gaillardia x grandiflora)
This tough, North American native blooms through summer with deadheading and can take the heat. Perennial blanket flower is also very easy to start from seed. There are lots of pretty varieties available, just be sure that the ones you choose are G. x grandiflora cultivars because most others are annuals. The sunny peach-flowered ‘Mesa Peach‘ is a very pretty one to try as is the red and gold ‘Arizona Sun‘.
SeedStarting: Cover seeds with a little seed starter, keep lightly moist, and maintain a fairly warm room temperature. Germination often takes one to two weeks.
Salvia (Salvia nemorosa)
Purplish salvia flowers line the upright stems of this salvia through summer with deadheading deadheaded. If plants are started in February or March, they should bloom in the first year. (Click here to see lots of seed options!)
SeedStarting: Lightly cover the seeds with seed starting mix and keep slightly moist. Place seed pots 4 inches from grow lights for best results. A heat mat can also be useful. Germination should take three weeks or more.
“I bought Black Gold potting soil with fertilizer for my herb, tomato, onion, and pepper seedlings. Do I also need to use liquid fertilizer once the seedlings grow their true leaves?” Question from Kim of Hiram, Ohio
Answer: It is important to be timely when fertilizing seedlings to give them the best head start. With that said, fertilizer in the soil can actually inhibit the germination of some seeds. (The salts in fertilizers disable the uptake of water in some seeds, which reduces or stops germination.) So, we recommend starting seeds in a mix that does not contain added fertilizer. Black Gold Seedling Mix is perfect for all types of seeds, and Black Gold Natural & Organic Potting Mix is a little coarser and great for starting larger seeds, like sunflowers, squash, and beans.
From there, start feeding seedlings with a 1/2 dilution of water-soluble fertilizer formulated for vegetables after they have begun to develop their true leaves. As they become larger, you can graduate to a full-strength dilution. I recommend waiting until they are 4-5 inches before feeding them fully.
“In seed starting, which plant benefits the most by having a grow mat under it?” Question from Tim of Burton, Ohio
Answer: Some seeds need supplemental heat for germination, and these are almost always seeds for warm-season crops that naturally sprout when the outdoor temperatures heat up. Summer flowers, like cleome, cosmos, coreopsis, gomphrena, marigolds, salvias, and sunflowers, sprout better and grow faster with added heat. When it comes to herbs and vegetables, think of anything that thrives during the warmest times of the season–basil, corn, eggplant, okra, peppers, rosemary, and tomatoes all germinate and grow best with bottom heat.
“Hi, I have the worst time starting seeds and am not sure what I’m doing wrong. Do I need to put a heating pad under the tray and a light on top? If so, can I use a regular heating pad for under them? Can I use a regular shop light above them? I cover them with plastic wrap until the seeds sprout, which hasn’t been happening, and then it gets all moldy. I just tried a tray of rock wool with 50 seeds! All I’ve got so far is mold, no sprouts. Every year I end up giving up and buying plants from the garden center. I have a lot of seeds, I collect and trade and I’d like to be able to successfully start and grow them. Thanks for your help.” Question from Lucia of Huntington Beach, California
Answer: Seed starting takes patience. The most common mistakes that gardeners make are that they plant the seeds too deeply, they overwater them, or both. Too little water is another common problem, especially when they are just beginning to sprout. A little dry soil can mean instant death to a tiny seedling. Here are my recommendations for each of your questions followed by some excellent seed-starting resources we have.
Do I need to put a heating pad under the tray and a light on top? Yes, to both, though not all seedlings require bottom heat. It is best reserved for warm-season vegetables and flowers, such as tomatoes, peppers, marigolds, cleome, and salvias.
Can I use a regular heating pad under them? No, regular heating pads cannot be wetted and may short out and start a fire. Seedling heat mats are not too expensive, they are safe, and just the right size for a seedling flat. (Click here to learn more.)
Can I use a regular shop light above them? There are lots of lighting options, with shop-light fixtures being the most economical. Some shop-light fluorescent bulbs are specially designed for plant growth and cover more of the spectrum–up to 94%. These are the bulbs to use. In general, fluorescent bulbs are not very strong, so they must be placed just inches above seedling flats or plants for best light reception and growth.
I cover them with plastic wrap until the seeds sprout, which hasn’t been happening, and then it gets all moldy. Your soil and seeds are too wet, so the whole lot is rotting before any growth can happen. Wash your pots well before you try planting again to remove any mold spores. Then fill the pots with fresh, moistened Black Gold Seedling Mix, sprinkle the seeds on top, add a light sprinkling of the mix over the seeds, and then keeping the tops lightly misted daily. (Click here to see a nice plant mister.) The soil should be kept lightly moist, never wet. For larger seeds, plant them 1 to .5 inches down, no deeper. Most seed packets recommend that you plant seeds too deeply.
From there, try reading a couple of these great articles about seed starting. We also have a video about starting tomato seeds below.
Are you low on cash but want a summer garden? No worries. Seed starting can be very inexpensive if you know where to shop, when to plant, and how to succeed with as few resources as possible. Fancy seed-starting flats are not needed, reuse instead. Pricy grow lights can be bypassed if you have sunny window sills. Some quality seed vendors are more reasonably priced than others. Here are these and more tricks for seed-starting on a budget.
Some seed vendors sell high-quality seeds for less–for me “less” means between $1.50 and $2.50 per packet. My all-around favorite seed vendor for quality and price is Pinetree Garden Seeds. I’ve purchased from them for over 20 years, and their prices, selection, and seed quality are always outstanding. Another great, reasonable seed source is Botanical Interests (their flower seed collection is especially nice).
Other seed sellers offer lots of seeds for less. High quantity is especially useful for gardeners that grow lots of row crops, like carrots, beets, and beans. Franchi Sementi (also called Seeds of Italy) is one the best for low-cost bulk seeds. (They also have fun European vegetable varieties.) Packets may cost $4.50 each, but most contain hundreds of seeds per packet! It’s a super value. Pagano Seeds is another source that provides lots of seeds for a good price.
Plants for Indoor Sowing: Small-seeded, warm-season vegetables, herbs, and garden flowers, such as tomatoes, peppers, eggplant, salvia, petunias, impatiens, and basil, are best sown indoors in containers. I also start cabbages, kales, and lettuce indoors because they germinate better. I generally wait until plants are 6-inches tall or more before planting them.
Plants for Outdoor Sowing: Large-seeded, fast-growing plants, or those that are sown in rows, are best planted outdoors. Cool-season vegetables, like peas, carrots, beets, and radishes, can be sown outdoors in rows in early to mid-spring. Warm-season, large-seeded crops, and flowers, like beans, corn, okra, sunflowers, and zinnias, can be directly sown in fertile garden soil. I tend to start my cucumbers, melons, and squash in 4-inch pots of Black Gold Natural & Organic Potting Mix outdoors in late spring. They germinate fast, and I let them develop several sets of leaves before planting them in the ground. (Click here to learn more about preparing vegetable garden soil.)
3. Reuse and Recycle
Frugal growers can cut corners by starting seeds in reused containers. Saving pots from the previous year’s nursery purchases is always an option if you have space, but, reused containers are also useful and educational for kids (reuse, recycle!). Clear plastic ventilated clamshell containers with lids and holes for aeration are especially useful. The lids can come in handy, and once they’ve served their purpose, I just recycle the cleaned containers.
When it’s time to upgrade seedlings into their own pots, there are lots of options, such as yogurt cups, cut plastic bottles, plastic cups, or washed tin cans with holes punched in the bottoms. Be sure to wash containers with hot, soapy water and rinse well before use. Halved toilet-paper tubes, paper egg trays, or eggshell containers are options for those who prefer paper or natural containers.
4. Choose Cheap Stakes and Labels
Every kid in grade school started beans or sunflower seeds in a plastic cup labeled with a Popsicle stick. You can still save the sticks as free planting labels. (These, or any wooden label, are best marked with a heavy graphite pencil.) Another option is cutting up large plastic yogurt or cottage cheese containers into strips and trimming them into 3-inch labels. Simply using a sharpy to mark the outside of a cup or container is another option, but it’s always nice to have a label that you can transfer into the garden at planting time.
The most inexpensive stakes for holding up small tomato seedlings are twigs collected outdoors and then cleaned and cut to size. Wooden or plastic stirrers can also serve as small stakes. I usually secure plants with pipe cleaners or soft twine.
5. Soil and Fertilizer
If you want strong, happy seedlings, don’t skimp on soil and fertilizer. Good products will ensure good seedling growth from the start. Black Gold Seedling Mix is ideal for seed starting. If you’re starting very small seeds, it pays to purchase Black Gold Vermiculite to gently cover them. Not only does vermiculite hold water to keep the seeds from getting dry, but a gentle sprinkling also allows light to pass for seeds that require light to germinate, like lettuce. Diluted, all-purpose, water-soluble fertilizer is gentle enough for small seedlings. Fertilization is not needed until sprouts have begun to put on their second and third sets of leaves.
6. Water for Success
Using the right watering techniques, from start to finish, is essential to success. Use tepid water–seedlings don’t appreciate the shock of hot or cold water. Keep the soil just moist, never saturated, to avoid seed and seedling rot. To avoid saturated soils, mist the soil surface as needed until seeds have sprouted. Once they have sprouted and start growing, water from the bottom to encourage deep rooting and maintain dry surface soi, which discourages shore flies and fungus gnats. (Click here to learn more about these pests and their control.)
7. Use Natural Light
For indoor plants, the cheapest light is free sunlight that streams through south-facing windows. Ample light is required to keep seedlings from stretching towards the light and becoming long and leggy. Six to eight hours of sunlight should be enough. If you have too little sunlight, fluorescent lights in a shop-light fixture are the least expensive supplemental lighting option. Some fluorescent bulbs are specially designed for plant growth and cover up to 94% of the light spectrum. In general, fluorescent bulbs are not very strong, so they must be placed just inches above plants for best reception and growth. Shop lights are easily set up above a basement bench, along a shelf, or in an informal office space.
8. Always Harden Seedlings Off
Hardening off seedlings prepares them for the travails of the outdoors. (Hardening off means acclimating seedlings from their cushy indoor growing conditions to the windy, sunny outdoors where temperatures fluctuate.) Indoor-grown seedlings are tender, weak stemmed, and need time to adjust. If planted in a tender state, they may develop leaf burn, suffer stem breakage, and die. Harden them off for at least a week before planting. Place the potted plants in a protected spot that gets a few hours of sun per day. Then move them a little more towards the light and in the wind each day. After a week or so, they should be tough enough to plant in the garden.
9. Know When to Plant Outdoors
It pays to know when to plant what outside. If your timing is off, excess cold or heat can be deadly.
Spring and Fall Vegetables: Cool-season vegetables, seeds and starts, can be directly sown in the ground in spring as soon as the soil can be worked. Amend the soil with Black Gold Garden Compost Blend, label rows, and cover newly planted seeds with a light layer of compost before watering them in. Keep them just moist, and they should sprout as the soil gets warmer.
Seed saving is easy, saves money, and ensures that your seeds have come from a reliable source (your garden!). Smart seed saving requires that you (1) allow your seeds to fully mature, (2) clean your seeds properly, (3) store your seeds correctly, and (4) know exactly what you are saving and storing. Step 4 is essential. If you are collecting seed from a known heirloom plant, you can feel pretty safe that the seedlings will perform like the parent plants. But, if you save seed from a hybrid, expect the progeny to be mysteries awaiting discovery because they may look nothing like the parent from which you collected them. (Click here to learn more about heirloom seeds, and click here for more seed-saving tips from the Seed Savers Exchange.)
“How do you harvest and grow peony seeds?” Question from Mark of Barrie, Ontario, Canada
Answer: If your peonies successfully cross-pollinated and produced viable seeds that can be induced to sprout, then the plants will develop seed pods that should contain fully mature seeds in late summer or early fall. The round, tough seeds should be harvested as soon as the pods open and begin to turn brown. The seeds will be dark brown to black.
Getting Peony Seeds to Sprout
It takes time and patience to get peony seeds to sprout. Some seeds will produce seedlings in a year and others can take up to three years. Fresh seed will yield the best results. The seeds require a process called stratification, which involves a chilling period of a few months before one can try to induce the seeds to grow. In the case of peony seeds, they need a warm period, chilling period, and warm period. Stratification can be done indoors or outdoors.
The outdoor method is a little less precise and may take longer, but it often yields the best results. As soon as you harvest your seeds, soak them for three to four days in water. Change the water each day. Unhealthy seeds will float, sink, and become soft. Healthy seeds will swell, and remain round and firm.
Collect the healthy seeds, plant them 1.5 inches down, and 3 inches apart in a flat of Black Gold Natural & Organic Potting Mix. It contains peat as well as composted bark–a combination favored by peony seedlings. Count the seeds and note their placement to keep track of their progress. Also, be sure to label the flat with the planting date, name, and any other essential information. Place the flat in a safe location in partial shade. Keep it moist through the warm days of fall, then cover the top of the flat with plastic wrap in late fall, and let it remain over the winter. Remove the plastic in early spring, and keep the flat moist through spring. The seeds should begin to sprout by mid to late spring. When they emerge, feed them lightly with a water-soluble, all-purpose fertilizer as soon as their second (true) leaves emerge. Once they reach a few inches, you can transplant them to pots or a location in the garden with good soil. You will need to baby them as they grow. It may be wise to protect them with chicken wire or plastic collars. Placing diatomaceous earth around them should also keep snails and slugs away.
Some seeds may not sprout in the first year. If this is the case, keep the flat in place, maintain moisture through summer, and repeat the stratification process in fall and winter.
Take your healthy peony seeds indoors, place a few in a 4-inch pot filled with Black Gold Seedling Mix. Moisten the pot, and place it under grow lights for a month and a half. Keep the pot moist and make sure the indoor temperature is between 70 and 80 degrees F. After a month, place the pot in an air-filled plastic bag in the refrigerator. The best temperature for stratification is 40 degrees F. Moisten the pot every couple of weeks while it is in the refrigerator–don’t let it get dry. After three months, remove and place it under grow lights. Keep the pots lightly moist, maintain a temperature between 70 and 80 degrees F, and the peony seeds should sprout in a month or two. A heat mat set to warm can help. (Please click here for more detailed information about how to start seeds indoors.)
“What is the best way to plant wildflower seeds. I am preparing a spot on a sunny hill, taking the grass and roots out down to the dirt. I know I have to mix the seeds with sand. Are there any other tips on making them thrive? I appreciate the advice. Thank you.” Question from Lexy of Weare, New Hampshire
Answer: There are some tricks to getting wildflower seed to become established when sown outdoors. For success, please follow these wildflower sowing tips from the western horticulturist, Maureen Gilmer.
Use new seed from local sources. Wildflower seed can lose its viability quickly, so use seed packed for the current year.
Apply the right amount of seed. Each seed mix will have its own designated application rate. A general rule of thumb is ¼ pound of wildflower seed will cover 500 to 1000 square feet. Make sure you get enough seed to produce the density of color you want.
Scar the soil. Annual wildflowers love the disturbed ground, so make sure yours is freshly tilled or hand-worked with an iron rake prior to sowing. Seed gathers in these furrows. (The first spring after World War I ended, the battlefields of France bloomed solid red with corn poppies that thrived in soils churned up by trench warfare.)
Cover seeds very lightly. Some wildflowers need light to germinate and remain dormant without it. Providing too much cover can spoil your efforts. Instead, sow the seed, then scatter Black Gold Garden Compost Blend in a thin layer over the top. It too will migrate into the furrows to keep seed lightly moist.
Weed to prevent competition. Spring weeds can devastate your wildflowers. As they begin to develop, pick out the grasses so they don’t compete for the same soil moisture as the wildflower seedlings.
Provide water during dry periods. If rains are poor, use a sprinkler to create rain-like irrigation every couple of weeks during the winter and early spring.
“I have some milkweed seeds and wonder when I should plant them. Should I plant now or wait until spring?” Question from Lynda of West Warwick, Rhode Island
Answer: Start milkweed (Asclepias spp.) seeds indoors in mid to late winter. The seeds of these long-lived perennials can be a little tricky to start because they require a chilling period before they will sprout. (Keep in mind that this only applies to temperate species. Tropical milkweeds, like Asclepias curassavica, don’t need stratification at all.) Here is a materials list and timeline of the steps needed to get these seeds to germinate.
Mid-Winter: Soak your seeds for half a day in lukewarm water. Sprinkle several seeds over small (4″) pots filled with moistened Black Gold Seedling Mix, and lightly cover them with additional mix. (The seeds should be placed about an inch apart. I suggest planting at least a two pots up to ensure you get at least a few seedlings.) Stick labels into each pot with the plant name and date started. Put the pots in large, sealed plastic bags, and then refrigerate them for four to six weeks. Make sure the mix remains lightly moist during this time. (This can also be done in plastic bags of lightly moist potting soil, but I find that the seeds are easier to find and manage if they are pre-potted.)
Early Spring: Remove the pots from the refrigerator, place them in water-holding trays, and lightly water them with lukewarm water. Set them in a warm, south-facing window or beneath grow lights. I prefer to start seeds beneath grow lights. (Click here for an article with an overview of starting seeds beneath grow lights.) Lightly spray the surface soil to keep it moist. The seeds should germinate within two to three weeks. Then water intermittently to keep the pots just moist.
Mid to Late Spring: Transplant the seedlings into their own small pots or into cellpacks, allow them to grow to at least several inches, harden them off, and plant them outdoors.
“How can I prevent damping off when I sow seeds? That is my problem.” Question from Bev of Philadelphia, Pennsylvania
Answer: This is a problem that I have faced many times starting seeds in university greenhouses, professional greenhouses, and at home. Thankfully, the solution is pretty simple, and it all involves keeping everything clean. Let’s start by covering the sources of damping off disease.
What is Damping Off?
Damping-off is a disease of sprouting seeds and seedlings that is primarily caused by two soilborne fungi, Pythium and Phytophthora spp. They cause rot and death in developing seeds and seedlings, usually at the roots or base of tender developing stems. Damping-off is a problem when growers keep the soil too moist and the disease is present.
To keep damping-off from taking hold you need to start with good soil, clean pots, and follow up with smart care.
Sterilizing Mix and Pots
Disease-carrying mix is the biggest concern. I used to work in large-scale greenhouses where they used big heater/steamers to sterilize mix at a temperature just high enough to kill any soilborne diseases (around 180°F). This is essential for growers that reuse mix, but careful growers sterilize new mix, too. Why? Because the airborne spores of damping-off fungi can be practically anywhere –especially in places where plants are being grown.
Additionally, unused seed-starting mix, like Black Gold Seedling Mix, is typically produced in clean facilities and bagged pathogen-free. But, if bags tear in transport and/or bags are not stored properly, Pythium and Phytophthora spores can infiltrate. Bags of seedling mix should be lightweight (meaning no water from the outside has seeped into the bag) and without tears. Improperly stored open bags at home can also be a danger. If you are not certain of your mix’s cleanliness, then it’s time for home sterilization.
I sterilize seed-starting mix using this fast and easy method.
Ingredients: Seed-starting mix, a 9″ x 13″ cake pan, 1/2 cup water, aluminum foil, and an oven.
Directions: Preheat your oven to 180°F, fill your pan with seedling mix, sprinkle it with the water, cover the pan with the foil, and bake it for 30 minutes. After baking, remove the pan from the oven and allow the mix to cool before using.
These diseases can also hang out on dirty old pots, so in the greenhouse, we’d also wash used pots and trays really well in hot water with good dishwashing liquid and sometimes a dash of bleach. I do this at home as well.
Seed and Seedling Care
Aside from starting with clean soil and pots, it is essential to discourage wet soils when starting and growing seedlings. I generally keep newly planted seeds gently sprinkled with a bottle waterer (see video below), so the soil is never over saturated. Once my seedlings pop up, I bottom water by adding 1/4 to 1/2 inch of water to the water-holding trays every two to four days, depending on seedling size. It also helps to encourage airflow, to help soil surfaces dry more quickly, and keep trays warm with a heat mat.
These cultural practices will definitely kick your damping-off problem away for life!