Winter is a great to time to start planning your indoor or outdoor edible garden for the year ahead. After you decide what to grow, the next step is to choose and then sow your seeds–tasks that can sometimes seem daunting to first-time or less-seasoned gardeners. We asked Matthew Hoffman, owner of Northern California’s The Living Seed Company, for his troubleshooting tips and recommendations for planting an edible garden that flourishes, no matter what your space or experience level . Read on for his expert advice on choosing, sowing and transplanting seeds and seedlings.
What seeds do you recommend buying for an indoor edible garden?
Grow what you love to eat! And don’t be afraid to experiment. Many herbs such as basil and cilantro will do great. Leafy greens such as, lettuce, spinach, kale, etc, are also very easy to grow and well suited for indoors. A vining bean or pea is a great decoration as well as an edible. Run the vines around a shelf or window. Kids love picking the green beans and peas and popping them in their mouths. Roots can do well indoors too. Try shorter varieties of carrots, beets and radishes. Tomatoes and peppers will work as well but need a larger pot, more space and more light. Of course I would recommend The Living Seed Company’s Urban Collection.
Starting in the early winter, the freshest seeds for that year become available. Seed packets will state which year they are packed for, but most will live a few years beyond. Over time, seeds will lose some of their viability. Seeds are alive–they should be kept in a cool, dark and dry place to extend their life. You could keep them in the refrigerator in an airtight container. If you do this, when you take them out make sure to leave the container out at room temperature until it warms up, before opening, to avoid condensation on the seeds.
What are the ideal conditions for growing seeds indoors?
Plants, especially vegetables, need sunlight. While leafy greens, carrots, peas and beets do not need a lot of direct light, they will grow faster the more they get. Tomatoes and peppers really need 6-8 hours minimum to produce fruit. A windowsill by the sink with sunlight can be a perfect place for some herbs or lettuce. A bay window can become your own miniature indoor dream garden. You can even hang pots to increase growing space. South facing windows will receive the most light. Be aware in the middle of summer that your plant friends will need more water if in full sun. If its really hot and intense pull them (especially the greens) back from the window a bit until it cools down. If lack of light is an issue, indoor grow lights can be used.
If you are using saved seeds, or seeds given to you by a friend, how do you determine the ideal depth for planting them?
Small seeds like carrots, lettuce, basil and kale should be planted just below the surface of the soil. You can place the seeds on the surface of the soil and sprinkle a little more soil (1/8 to 1/4 inch) on top. Larger seeds like beans, peas, squash and corn, can be planted about three times their width (a 1/2 inch bean about 1 1/2 inches deep). Make sure to keep the soil moist but not waterlogged as young sprouts are very delicate.
Yes! Saving seeds is one of the most rewarding activities a gardener can do. Not only do you benefit from having more seeds to plant, the seed will adapt to your particular climate and bioregion over time. Just imaging your favorite varieties doing better and better over the generations. Plus, it is truly amazing to be part of the miracle of plants producing an abundance of seed and completing their life cycle! Seed saving can be simple or complex depending on the type of seed you are saving. Self pollinating perfect flowers like those on beans, peas, lettuce, tomatoes and peppers can be very easy to save, with out worrying too much about cross pollination. For beans and peas just let some of the pods dry down completely on the vine. You can then shell the seeds and plant again next year.
Be sure to save seeds from numerous plants to avoid inbreeding depression, which will weaken you plants vigor and resilience over the years, do to genetic bottlenecking. Let lettuce flower (also known as bolting) and once the pretty little yellow flowers are dried out, looking somewhat like a miniature dandelion, shake the flower heads into a paper bag every few days until you have the amount of seed you desire. Pepper seeds can be removed from the flesh and placed on plate or cookie sheet to dry in a warm (not over 95 degrees F), dry place out of direct sun. When the seed snaps between your finger nails, it is dry enough to store. Tomatoes benefit from a fermentation process that treats the seed for seed borne diseases. Cut the tomatoes in half at the equator. Squish the seeds and juice out into a jar. Place jar in a warm area (on top of the refrigerator is great). After two to four days a mold (that co-evolved with the original wild tomato) will appear. The seeds are then ready to be cleaned. Fill the jar with water and stir. After a few moments the good seeds will sink to the bottom and the bad float to the top. Carefully pour off the bad seeds, any skin or flesh and the mold. Repeat until water is mostly clean then pour the seeds into a strainer. Remove any remaining debris by hand. Empty seeds onto a plate or baking sheet and place in a warm, dry place. When seeds are dry, using the finger nail snap test, you can safely store the seeds.
Other seed saving can be a bit more complex. Biennials such as carrots and beets take two years to produce their seed and may require removing the roots from the soil if being grown where the ground freezes. Other vegetables like squash, cucumbers and the cole crop family (broccoli, cabbage, kale, etc.) can cross pollinate with members within their species quite easily and measures need to be taken to prevent this if more than one variety is being grown and pure seed is desired. If you really get into seed saving, I recommend picking up a book on the subject as their are many wonderful techniques and tips for seed savers.
How do you really know when your seedlings are ready to transplant?
If starting from flats, transplant into a container when the first true leaves emerge when the seedling is still very young. These seedlings may then be transplanted again outside or into a larger container when they develop more but before they become root bound. When transplanting to the outside, you will need to toughen them up for the outdoors by hardening them off. Stop feeding them and water them less. Start putting them outside in a protected area out of wind and direct sunlight or in a cold frame. Start for a hour, then two, then a few hours in the morning, gradually building up time outside over a week or two avoiding extreme weather. Then they are ready to transplant.
Seeds do not need fertilizer or even soil. How cool is that? Once the baby plant emerges it will require nutrition. If using a soilless potting mixture, the seedlings will need regular fertilization after the first true leaves appear. Fish emulsion, compost tea or manure tea will work great. If using a soil-based potting mixture that has compost or other nutrients, fertilization may not be needed for several weeks.
Yes to composting! You can make your own in a compost bin or worm farm. It is so rewarding to take your vegetable kitchen scraps and leftovers and turn them into nutrient rich compost that you give back to your plants and garden! Add compost to the garden soil or containers before transplanting.
How do you estimate the last frost date?
For likely the most accurate information I would go to the National Climatic Data Center . They will provide frost probability levels at 10, 50 and 90%. 10 % probability will be the safest date. Some places, like where I grew up in Northern Wisconsin, can have frost almost year round, yes even in July! If you live in such a place, plant when frost is no longer a regular happening and pay attention to the weather. If it’s going to frost in July, cover your tender plants like tomatoes and peppers.
What type of soil amendment do you recommend for replenishing raised beds or in-ground garden plots?
It can vary greatly depending on your soil. If you really want to “dial in” your soil, get a soil test done to know what you are starting with and amend with what is recommended by a trusted testing company. Remember organic is healthier for you and your soil. Compost and worm castings are great. Apply liberally when transplanting and during the growing season as a mulch or side dressing. Another great way to build soil, while conserving water and suppressing weeds, is to mulch with straw (not hay) around your plants and turn it in at the end of the season.
Where should I put my sprouting seeds?
When sprouting seeds indoors keep them in a warm place in the house. Near a hot water heater or on top of a refrigerator is ideal. Make sure to check on them in 2 to 3 days. Lettuce seeds need light to germinate. Once the sprouts emerge from the soil the baby plants will need plenty of light. Seedlings need more intense light than full grown plants, 12 to 16 hours a day is best. If the seedlings a growing long, pale and spindly they need more light. Seedlings do not need as warm of temperatures as germinating seeds. Seedlings also need regular moisture and a reasonably high humidity. Do not over water seedlings, evenly moist but not soggy. A couple light mistings a day will help.
You could do a germination test but that would require you sacrifice some of your seed and take some extra work and time. If you want to make sure they are viable before you go through work of planting them, this is what I recommend. Different varieties have different average life spans under ideal storage. For instance, lettuce seeds are viable for about 6 years while onions are only viable for a year or two. These are just general guidelines not exact measures. There are plenty of stories of very old seeds still being viable, so take good care of them. The oldest verified seed to sprout was a Judean date palm that was 2,000 years old!
My seedlings died after transplanting. What could have gone wrong?
The seedlings might not be dead! Keep watering them regularly until you are sure they are dead or they come back to life. Sometimes plants drop off (look wilted or dead) after being transplanted and then come back in a few days. There are almost an infinite amount of variables when it comes to gardening. One major problem with transplanting is not “hardening off” (acclimating for the outdoors) the plants properly. Be sure to transplant on a cloudy or misty day or late in the afternoon to avoid being burnt by the sun. Be very careful with the fragile root system as well.
For most growing regions, it is best to start seeds in the late winter (to transplant) and spring if growing outdoors. If you are growing indoors and have a window with sunlight or indoor grow lights you can grow year round. If you are growing outside it really depends on your climate. If growing over the winter, you will want to plant seeds in the late summer through mid autumn to give your seedlings enough light to grow and survive through the darker part of the year. Here where I am in coastal northern California we are blessed with the ability to grow some varieties year round. Even though it frosts here, the varieties we grow are “frost tolerant” vegetables like beets, carrots, peas, spinach, broccoli, cabbage and lettuce that like it cool. Varieties like Red Russian Kale are even able to survive at 10 degrees below zero F! Picture digging through the snow to come upon some sweet, tender, green and purple leaves in the middle of January! I recommend gardening and growing as much as you can get away with!