How early can we begin direct sowing outside?

I'm a huge advocate of starting some of my frost-tolerant crops very early. This isn't necessarily the best practice for all gardeners or farmers, but there are some practical reasons for group gardens to get a jump on the calendar for early crops, some of which will be harvested early to be replaced with another crop for succession planting.  These are all the frost-tolerant crops mentioned in other garden planning postings, such as peas, fava beans, radishes, arugula, turnips, spinach, etc.  As long as the garden is being planted, I would also start the frost-tolerant, full season crops like kale, collards, chard, beets, etc.

Here, I'm only referring to planting in the open with no row covers or hoop houses.  Using those for season extension is another subject that I'll discus in the future.

My opinion on early sowing is based more on human scheduling complications, rather than science, climate or gardening. While many gardeners or farmers in NYC will start their frost-tolerant early direct sowing around April 10 or 15, I like to start during the last week of March and have even started as early as March 15. I just see more upside and little downside in doing so. 

When working with groups of volunteers or classes at a school garden, sometimes the scheduling is based on peoples' availability, not the outdoor climate.  If we scheduled the initial planting for April 15, and any given delay was to occur, the planting may not happen for another week or two.  Some of my gardens are only worked on during the weekends, and some of the school gardens have classes that follow a strict day-of-the week schedule.  There could be rain outs, Spring Break, field trips, school assemblies, etc., so rather than risk a late start, I would err towards early.  New York City's public schools schedule their Spring Break around Easter, so I always try to schedule some of the planting before, and then some after the break.  If a few classes don't get outside until mid-April, most of the garden is already planted, so we're off to a good start.  If a school garden is ran by teachers that can just plant when the weather is fine, I would recommend a later planting date, but the gardens that I run rely on an outside coordinator (me) with specific times scheduled.  I hope these non-gardening complexities are clear(?).

Another upside to early sowing is that if we happen to have an unseasonably warm early-April, our crops will get a great head start. If we have a cold April, they'll probably linger and then not grow any quicker than the crops sown in mid-April. But, so what...?  We shouldn't be any worse off than the later starters.  I personally have had no crop losses due to early sowing. The only danger that I could foresee is that if it's unseasonably warm at germination time, and then after most seedlings have germinated, there's a small snow storm that crushes everything. It's not the frost, but the snow that I worry about. Or, very, very cold frosts, not merely dipping a little below 32. But, the typical scenario would be very little germination during the first week or so, and then by the time the seeds are emerging, it's already a bit past the risky dates. Those same risks are why I would not sow these seeds during a warm early March. The likelihood of a crop failure greatly increases if we start earlier.

Still, my opinion here is evolving. This is just how I have been doing things during the past few years. This March, two of my schools began sowing shortly before or after a small snow storm.  In years past, another one of my gardens did all the early sowing in late March when the thermometer registered 28 degrees.These  seeds didn't actually germinate until it was warmer, but we suffered zero casualties and had no regrets working on a sunny but cold (and thankfully windless) day.  Just not a huge head start, but good to get the work done and over with.

Just to add a contrary opinion...  I was told by one organic farming guru from Western Massachusetts, that we should start a bit later because the plants do better when they get off to a quick and strong start, rather than lingering. I'm still deciding whether that's important for smaller scale, non-money making operations, or if urban gardeners (but not farmers) should follow the schedule that I advocate, just to stretch our scarce land a bit more.  For now, I still believe that there's little to no downside in getting things started early.

One of my garden plans explained

In February I gave some quick tips on garden planning, using a simple 4' x 8' grid. Here I'll explain a few of my actual garden plans that have less regular, more complex shapes.

As for simple 4' x 8' gardens, last week I planted several with elementary school classes, and they didn't really require a drawn out plan. Rather, we just kept in mind where the warm weather crops would later be placed, so planted radishes, arugula, spinach or lettuce there...to be harvested and replace by mid-May or June.

Now...for more complex planting schemes. Below is the plan for a school garden that had to be carved up into 17 spaces for 17 classes. I wanted each class to experience more than just “planting lettuce” or any other singular crop, so I'm giving all some succession gardening, while also creating a plan that makes sense as a whole.

 Before I explain the details of this early growing plan, it's worth showing the warm weather plan, which really dictates where short season plants can be sown earlier during the cold months.  So, let's skip over to the next diagram...

Warm weather plan....

 So... above I have in the red font, all plants that will be planted after the last frost.  There's also plants in blue font.  Those are the frost-tolerant plants that were direct sown earlier in the season, but they have long growing seasons so will occupy the space for the entire season, rather than making room for succession planting.  You'll see a lot of the brassicas such as kale, collards and kohlrabi.  Also, beets and chard.  Those just consist of two species.  Then, there's also potatoes, and nasturciums. 

Now, backtrack to the early planting plan....

All of the frost-tolerant plants that I previously mentioned are also in this plan.  The big difference is that the warm weather plants that were in red font, are now replaced by frost-tolerant, short season plants in blue font.  These all will be harvested before the warm weather plants are planted.  Or, sometimes they grow side-by-side for a short time.  

Another difference in the early and late planting plans, is that some of the companions in the early plan just drop off for the late plan.  One such common planting scheme is to plant radishes next to beets or chard (two varieties of the same species).  The radishes germinate quickly, produce quickly, while the beets or chard emerge more slowly.  The beets and chard don't really need the extra room until it's time to harvest the radishes.  In a school garden, it's important to tell the kids and teachers to be very careful to harvest only the radishes and be careful to not damage the small chard or beets seedlings.

Here are some explanations of good succession pairings, where one crop is completely harvested to make way for the next.  It's good to understand that all "short season" and "warm weather" plants aren't harvested or planted at the same time.

Radishes, arugula and spinach early; nightshades (eggplants, tomatoes, peppers, etc.) late.  Those first three are the quickest grown and harvested.  Radishes happen to be a bit quicker, but all could be harvested quite

early.  All will bolt (or go to seed) pretty early if left in the ground, so there's not even an option of keeping them in the ground for longer.

Lettuce early; nightshades late.  Lettuce takes a little longer to reach it's full potential relative to the radishes, arugula and spinach, but it can still be harvested ahead of schedule, or perhaps grown side-by-side with it's successor.  But, don't feel you need to save the lettuce, as a good looking plant will taste bitter by the warm summer months.  It will also eventually bolt, but just a bit later than the arugula.

Turnips early; okra late.  Turnips sometimes take a bit longer to produce, when compared to the other short season crops.  I've had some in the ground until early July, which is too late to plant the nightshades.  Okra is a perfect fast growing hot weather crop that can be planted as late as early July...although I would still try to plant them early.  It's just nice to know that there's a good option to use that space.  Fava beans would be another "longer of the short season crops" that can be succeeded by okra.

Eggshell Seed Starting

A very simple and fun way to start seeds and reduce waste at the same time, is to use eggshells for seed starting.  Rather than starting seeds in a conventional way, we can use egg shells filled with soil.  Seeds can be started in the shell, and then the entire thing can later be planted in the ground.

Steps
1.    Collect eggshells, trying to keep around 2/3 intact.  This is easy but just takes a small amount of effort.  Rinse eggshells and store them in an egg carton.

2.    Poke a drain hole in the bottom of eggshells.  (not necessary if they'll be watered gently, but remember to later break a hole if transplanting outside or to a larger pot).

3.    Fill eggs with moist soil or seed starter mix.




4.    Sprinkle soil with seeds.  Some planting options:
   
    - Indoor sprouts or micro-greens, if you don't plan to replant these.  Lettuce, arugula, watercress, beets, chard, kale, kohlrabi, etc.

    - Plants intended for transplant, tomatoes, eggplant, peppers, kale, kohlrabi, marigolds, zinnias, beans, etc.  Basically, any plant that you would start indoors...so the list is infinite.

    - Cute decorative plants, such as grass or wheat.

5.    Keep watered.  If you did not poke the hole, make sure you don't over-water.





6.    Harvest micro-greens, or later transplant into the ground or a pot, eggshell and all.

 

Notes on eggshells
Eggshells are a great source of calcium for the garden, and these intact eggshells will be a slow-release mechanism.  Eggshells on top of the soil are a great slug deterrent, so crush all other eggshells and add them to your soil.

Growing Potatoes

Potatoes are closely related to tomatoes and other members of the nightshade family, including eggplants, peppers, petunias and tobacco.  Unlike their warmer weather relatives, potatoes are from a cooler mountainous region of the Andes Mountains in South America, and after Europeans brought them across the Atlantic Ocean, they have become a food staple in many countries that do not have long and hot growing seasons.  Potato plants store energy in their roots, which form tubers, and these tubers also allow them to reproduce.  Rather than planting seeds, we generally plant smaller tubers to grow more potatoes.  This type of reproduction produces identical genetic clones of the parent plant.

 

Steps to grow potatoes.     

Step 1)    Purchase organic potatoes from your local grocery store or farmer’s market.  Conventionally grown potatoes are usually treated with chemicals that prevent eyes from growing; however we need these eyes to grow our potato plants.  When a potato produces little sprouts, those sprouts are often referred to as “eyes”.

Step 2) Place a few potatoes in a dark and cool place.  February or early March is the ideal time to do this.  Occasionally check to see if eyes are forming.

eyes starting to form

Step 3) After a few eyes have formed, and a month before the last frost, cut potato into several one or two inch pieces, each having at least one eye.  Let these sit in the same cool, dark place for a few days or longer, to form calluses on the exposed flesh.

Step 4)    Plant potato pieces on top of a few inches of compost or dirt, with the eyes facing upward.  These eyes will become the plants, not roots, so it is very important to not point them downward.  Cover with a few more inches of soil or compost.  It’s best to plant in a deep container or trench, so you can build layers as the plant grows.  Tubers will grow out of the stem as more of the plant is covered.

Step 5)    Soon there will be very unique looking little sprouts, and soon these will form leaves that seem more developed than the typical seedling.  The small plants will grow very fast during their first couple of weeks.

Step 6)  When the plant is eight inches tall, bury half of it with compost or soil.  Keep repeating until you run out of space or the plant blooms.  As mentioned above, we bury part of the plant so the formerly exposed stems will produce more tubers once underground.  This will greatly increase the yield of potatoes, as the roots and tubers to do not keep growing deep into the ground.  So, to create more layers of tubers, we have to keep raising the dirt level.

Step 7)  When the leaves start to wither and die, stop watering for a few weeks and then harvest.  Dig gently around the plant, being careful not to bruise the potatoes.  If potatoes are growing in a container, it’s easier to dump out all of the dirt and look for the potatoes, rather than dig for them.

Step 8)  Brush off excess dirt and leave potatoes in a root cellar or a dry, dark place for a few weeks.  This will allow the skin to cure and then the potatoes will be able to store for many months.

Growing Sweet Potatoes

Sweet potato vines have traditionally only been grown for food in warmer climates, while mostly only enjoyed as ornamental vines in the cooler north.  Now, due to global warming, more sweet potatoes are also being harvested further north.  These may require a few months to sprout, so it is best to begin indoors in January or soon after. 

The sweet potato (Ipomoea batata) is actually not related to the potato, but it is a family member of the morning glory and moon flower. 



Steps to grow a sweet potato.

1. Slice sweet potato in half lengthwise.  (Or ask your parents to do so, if you are too young to use a knife.) 

 

2. Poke three toothpicks in the upper half of each piece.

3.  Place sweet potato in a jar of water, and put this on a window sill. 

4.  Leave it there for a few months, adding water as needed.  Be patient, and only throw it away if it gets extremely moldy or rotten.  Try a few in case one does not succeed. 

5.  Eventually several shoots, which we call slips, will grow.  After the slips start to form roots and small leaves, you can detach the slip and plant in a pot with soil.  If the slips only have leaves, you can remove the slips and put them in another jar of water and they will soon grow roots, and then can be potted.  Also, if the slips seem to be growing upside down, then just flip over the sweet potato. 

6.  Place outdoors (or replant if desired) in May when it's warmer outside.  During the hot months, it should grow very quickly, and soon you will have a beautiful sweet potato vine!

Indoor Seed Starting

I try to grow nearly all of our our plants by seed. Many gardeners will rely on buying transplants, either from a lack of planning ahead, or else due to the misperception that indoor seed starting is difficult. As an urban gardener (and apartment dweller), I know that space is a valid excuse, although I still make do with my windowsills.

Is fancy equipment necessary? Definitely not. I've never used a grow light in my apartment, as most plants do pretty well with natural light. The school gardens that I run all have grow lights in the classrooms, and they do indeed speed up the process and make it even easier, but still not absolutely required. A little more care is needed without grow lights.

What and when do we start seeds? This varies by variety, and most seed packets will have instructions. In New York City, I tend to start many of the nightshades, cabbages and other warm-weather transplants around March 1, to be planted 8 to 10 weeks later (by early to mid-May). Wait until early to mid-April to start cucumbers and squash, as they are transplanted as young seedlings, otherwise risk being too stringy and delicate. Beans could also be started indoors a few weeks earlier, but I always direct sow them.

Supplies

Water tight trays. You can purchase a cheap seed starting tray system, or you can reuse some plastic household items, such as the take-out Tupperware containers or plastic salad containers.

Clear lid. These would be included in a seed staring tray system. The reusable containers can be covered with another clear container or plastic wrap. The salad containers are easiest because identical containers can be used for both the tray and the top.

Jiffy Disks

Jiffy disks or earth plugs. These are the easiest things to use, eliminating the mess and effort of mixing soil and filling little pots or cells.

Or, rather than using the above, you can purchase small peat pots or seed starting cells, and add seed starting medium, coconut choir or a fine and spongy soil. This is the most cost effective way for larger seed starting operations, and this is what we use in most classrooms.

Steps

• If using disks, put in bowl or tray, and fill with warm water and wait for them to expand.
• Place disks, plugs or filled cells/pots in tray.
• Add seeds, cover (as per instructions)
  • if using disks or plugs, just push the seeds in the required depth, or sprinkle with fine soil or vermiculite.
• Place plastic lid on top.
• Put in sunny window
• Keep the tray damp but not swamped. Add water before it dries out, watering from bottom, not directly onto seeds.
• After seedlings germinate, remove lid.
• As seedlings begin to outgrow their space, you may need to transplant them to a larger pot...if they are not yet ready to plant outside. Hopefully this step can be avoided.
• Harden off seedlings a week or two before they will be planted
  • seedlings will be shocked when planted outside, so need to be gradually acclimated to wind, sun and varying temperatures. Most importantly, planting in the ground (or large container) can cause a large amount of shock that can prove fatal for many seedlings.
  • If possible, you can bring seed trays to a sheltered, shady are for a few hours per day, gradually building up the amount of exposure. This is a lot of work so I only encourage people to do this if it's convenient.
  • More practical and realistic, you can leave them outside, away from too much direct sun and wind. Just keep seedlings monitored, and bring them in during any extreme weather changes (storms, early heat waves, late cold spells, etc.), but otherwise just leave them be, and after a week or two they will be ready for the ground.

A Few More Steps to Make Seed Starting a Success

Here are a few extra steps that may come in handy...

• Sterilize growing trays
  • With larger production greenhouses or farms, it is important to prevent blight, molds or any pathogens that can destroy entire crops. Thus sterilization is recommended.
  • A small school or home operation usually doesn't need this; I've been only rinsing my trays for years, and no problems.

• Option 1. Bleach bath (1:50 bleach:water) in warm water.
• Option 2. Run through dishwasher

• Pre-germination
  • Some types of plants are tougher to start and take longer to germinate. Even within the same species, certain heirloom varieties, or also older seeds, take longer to germinate. Others are prone to get stuck in their stubborn seed coats. Pre-germination speeds up the initial germination, and then sprouts will be planted in seed trays. I usually pre-germinate all nightshades, squash/cucumbers, Moon Flowers, sorghum, and others.
  • Step 1: Soak seeds over night.
    

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  • Step 2: Place a bunch of seeds in a damp paper towel, but make sure they're spaced an inch or so apart.
    
    
  • Step 3: Place paper towel in a ziplock or tupperware, and seal. I usually fold the towel gently so it fits. Place in a dark, warm area.
  • Step 4: Check every few days. It's important to transplant sprouts soon after they sprout, and also find and remove any moldy seeds.
  • 

    Step 5: Transplant to the growing medium. I usually use a toothpick or chopstick to make a small hole and bury just covering the roots but not stem. Don't be intimidated in handling delicate seedlings, but just do everything gentle, and if one breaks, discard and plant another. The pale seedling will turn green after a few days of light.