Planting Asparagus Crowns

Asparagus may just be one of those things that it is impossible to have too much of - those tender, juicy, tasty shoots that emerge as one of the earliest vegetables of spring are pretty hard to beat.  I know some people claim to not like asparagus, but I am always suspicious that is only because they've never tasted it.   When one of my nephews was about six years old, Mom had prepared a huge batch of creamed asparagus for supper.  My nephew adamantly insisted he was NOT going to eat any "sparegress".  His dad told him this was not "a-spare-a-gus" but instead was "az-pa-raagus".  He ate his first helping of "az-pa-raagus" and asked for more.  Not only is it tasty, asparagus is highly nutritious, with an abundance of the B vitamins, vitamin C, calcium and iron. 

In Tuesday's blog I talked about soil preparation for transplanted asparagus crowns.  The same preparation to create a loose, well-drained soil is critical for new crowns.  A soil that is light and well-ammended will warm up more quickly in the spring, bringing those wonderful shoots to the dinner table that much sooner.

The variety of asparagus planted makes a difference in the type of harvest obtained.  Asparagus plants are male or female.   The male plants don't have the responsibility of producing seed, so they put their energy into producing fatter, more abundant spears.  The absence of seeds also assures they don't become pests when the birds spread the seeds to places where they aren't wanted. 

The Jersey Knight and Jersey Giant varieties are all male or nearly all male plants.  Jersey Supreme is also a primarily male variety that produces spears much earlier each spring than other varieties.  The heirloom varieties, such as Martha Washington, Mary Washington, and Purple Passion, are varieties that have both male and female plants, but tend to be long-lasting good producers.  Purple Passion will produce thicker, meatier spears than the other male / female varieties.

If planting all male varieties, it's recommended to plant six plants per family member.  For male / female varieties, the recommended number is 12.  I like to have enough asparagus to freeze or can for off-season use, so I plan to plant about three times that many.

Asparagus can be started either from seed or from divided crowns.  Starting an asparagus patch from seed is only for people who are more patient than I - it takes three to four years of growth before harvesting any significant quantity of asparagus from a seed- started plant.  Crowns can be purchased as either one or two year crowns and will produce within one to two years.  Crowns should be firm with plump, succulent roots and free of any evidence of disease, such as mold. 

Asparagus crowns are best planted in trenches about a foot wide and six to eight inches deep.  To give the crowns a little bit of a boost, they can be soaked in compost tea for 20 minutes before planting, but this isn't required. Place the crowns in the trenches 1½ to 2 feet apart and top them with about three inches of soil.   Every couple weeks, add another inch or two of soil, until the soil completely covers the crowns and is slightly mounded above surface level to allow for settling.  It is important to plant the crowns deep enough so that as they naturally rise from root growth, the crown does not become exposed.  Planting them deeper also helps anchor the asparagus plant so wind and rain doesn't affect its stability in the ground.

Keep the asparagus moist and weed-free.  Asparagus should not be harvested in the first year after planting.  If using two year crowns, small amounts of asparagus may be harvested in the second year after planting.  Only spears that are the size of a lead pencil or larger should be harvested.  Two year crowns should only be harvested one or two times the year after their first full growing season, and then left to grow for the rest of the summer.  Generally, year three and on, asparagus can be harvested for the full season.

 The harvest season for asparagus is eight weeks from the time of first harvest to last.  Harvesting for longer than that can weaken the plant and decrease production the following year.  The spears should be harvested by cutting about one inch below the ground with a sharp, serrated edge knife, or by holding the spear close to the ground and snapping the spear free of the crown.  If using a knife, caution is required to avoid damaging the crown. 

Asparagus spears should be harvested when they are about six to eight inches tall.  Longer spears may be tough and stringy.  In cooler temperatures, asparagus will usually be ready to harvest every other day.  As the temperatures become warmer, harvesting will likely be a daily event - asparagus spears can grow up to six inches in one day.

At the end of the eight week harvest period, leave the spears to grow into fronds.  These fronds will help nourish the root and get it ready for next year's harvest.  When the fronds have dried off in the fall, remove the dead foliage and destroy it to prevent spreading diseases in the bed.  I recommend top-dressing the bed with one to two inches of compost each fall to give the plants a boost up for next year's production.

But, in the meantime, enjoy that delicious asparagus.

Asparagus Dividing and Transplanting

As seems to be par for the course in our part of the world, once the rain started it can't seem to stop.  Not that I'm complaining, but it is causing me to fall way behind on my spring chores.  And this is a year when I really wanted to get a good running start to the season.  The house and yard needs to be in tip-top shape for our daughter's wedding on July 5.  Well, actually, it needs to be in tip-top shape for her garden party bridal shower three weeks earlier that that.... oh my!  I'm running out of time!!

Fortunately, I did get the major job of re-locating the asparagus bed finished before the rain started again.  My old asparagus bed has produced well for about 15 years, but as the trees grew taller and shaded the area more, and as the asparagus clumps started to become crowded, my patch started losing some of its "oomph".  The spears were getting skinnier and fewer, so the old bed has been re-located and some new plants started in an area that should be good for the rest of the asparagus' life.  At least I hope so, because moving asparagus is not a pleasant job. 

Asparagus develops a huge mass of thick, tuberous roots that spread everywhere in the patch.  Most gardening experts, when asked how to transplant asparagus, are likely to tell you to just buy new crowns and start over.  Yes, it's that much work to transplant them.  But, there is enough of my frugal mother in me that I just couldn't bear to see that old bed go to waste.  Plus, I have a sentimental attachment to those asparagus plants - Mom and I dug them from some overcrowded clumps in her garden all those years ago.  So, last fall I began the process of getting ready to transplant asparagus this spring. 

Those preparations started with preparing a new bed area in a nice, sunny location that isn't likely to become too shaded anytime within the next 50 years or so.  Asparagus likes rich, loose, and well-drained soil.  To accomplish that with my clay base, I added an extra helping of peat moss and well-composted manure to an area that had already been heavily ammended annually for the past several years.  We tilled those organic ammendments in last fall and then tilled it again this spring to loosen it up and make sure they were well mixed into the soil.

I also left the old foliage to dry in place last fall, rather than cleaning it off as soon as it was dry as I usually do.  That assured I could see where to dig this spring.  Ideally, asparagus should be moved while it is dormant, but it is pretty tough stuff.  Some of mine was growing nicely before I got it moved, and it's hardly complained a bit since it's in its new location.   In warmer climates, asparagus can be moved in the fall, but here, by the time it goes dormant, we are pretty near to the time when soil temps are too cold to allow good root establishment before winter freeze-up.

The important thing is to not damage the crown of the asparagus as that is the part of the plant that sends up those tasty, succulent asparagus shoots.  You'll almost always need to sacrifice a few of the roots in the moving but the asparagus will survive nicely if the crown is lifted intact. 

Start the process of moving by looking for where the old foliage is most closely clustered together - that is where the crown is located.   Then go about 8 to 10 inches further out from the edges of the old foliage to get the best clump of roots.  Do the initial digging with a spading fork or potato fork.  The tines of the fork will slide between the fat roots and loosen them before using the shovel to begin digging.  Once things are loosened up a bit, start digging down to the bottom of the root mass. 

Dig a circle around the clump, to the depth of the spade.  Then dig under the root system until the clump is free and can be lifted out of the hole.  There is no way to get all the root system so the objective is to get as much of it as possible.  The more root transplanted with the crown, the better chance of survival the plant will have and the sooner the crown will be able to produce large enough spears for harvesting.

Some of my clumps were about two feet in diameter and felt like they weighed 100 pounds.  I worked these out of the hole and onto an old plastic child's sled to move to their new location.  I've found that asparagus generally tells you where it can be divided - once the soil is loose, the crowns will often separate themselves and you can tease the roots apart and move an intact piece of crown to a new planting hole.  Smaller clumps were able to be moved and transplanted without dividing.

The transplants were planted in rows that are approximately 30 inches apart and each plant within the row is about 18 inches from its neighbor.  This should give my transplants ample room for many, many years without being divided and transplanted.  Asparagus plants can live up to 50 years, so it pays to plan ahead.

The roots should be nicely spread in the planting hole.  Begin covering the roots by gently sifting soil over the top of them by hand.  Don't use a shovel to dump a large amount of soil over the top of them at this point.  Once the roots all have a layer of soil to hold them in place, continue covering with a shovel until the crown of the asparagus is covered with approximately three inches of soil. 

The soil should be gently tamped down into the planting hole and the plant should be watered in well.  Asparagus is a pretty care free plant, so other than keeping the bed weed free, giving the plants a good, healthy drink of water every week, and a top-dressing of compost or manure over the top of the bed each fall after the bed goes dormant, asparagus doesn't ask for much to reward you with many tasty meals over the years.

Thursday we'll talk about planting the new crowns I bought this year.

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Caring For Strawberry Beds

Well, on Tuesday we planted the strawberries.  Now, how to take care of them.  Shortly after planting, you should begin to see new leaves emerge, followed fairly soon by flower buds.  Hard as it is for me to do, it is important to pinch off those first flower buds to allow the plant more energy to put towards strong root and plant development.  For june-bearing strawberries, this means you sacrifice the entire first season's crop, but you will be rewarded with much greater production in the following year.  For day-neutral and ever-bearing varieties, pinch off the blossoms for about the first six weeks of growth.  If the plants seem to be growing vigorously after that, it is ok to allow them to produce berries.

Strawberries need at least one inch of water per week.  It is best to water them deeply once a week, rather than giving them small amounts more frequently.  During very hot, dry, windy weather, your strawberry bed may require up to two inches of water per week to keep the soil consistently moist.  Always water your strawberries in the morning, if using overhead watering systems.  Strawberry plants are prone to fungal and bacterial diseases that thrive on wet foliage.  Watering in the morning gives the foliage the opportunity to dry off quickly.  Using a drip irrigation system gives you more flexibility in when you water because the water never touches the foliage, but it is important to not ever have water standing in your strawberry bed.  Not only will that foster diseases, but the strawberry crowns can suffer rot very quickly if the soil is not well-drained.

It is also important to weed diligently in the strawberry bed.  Beds can be quickly overtaken with weeds or renegade grasses, especially quack grass.  Berry production will be significantly inhibited if the plants need to compete with weeds for moisture and nutrients.  Laying mulch between the rows of the strawberry bed can help with this.  I use several layers of newspapers, covered with clean straw and this keeps the weeds down with very little cost to me.  You can also use landscape fabric or any other type of weed blocking substance.  It is not recommended that you use a pre-emergent herbicide, such as Preen, on your edibles.  There is a form of Preen that is formulated for use on edibles, made with corn gluten.  I personally have not seen much difference in weed production in those areas where I've tried the corn gluten products and those where I haven't used any type of pre-emergent herbicide, so I've decided to just save my money.

Runner plants will begin to emerge in early to mid-summer.  These can be left and allowed to fill out the spaces between plantings, but for ease of picking, it is a good idea to keep the rows open.  Any plantlets that crawl over the mulch between the rows can be gently lifted and place back into the row or snipped from the runner and moved to a new location.

Strawberries are prone to fungal diseases, such as root rot, gray mold, powdery mildew and botrytis.  Keeping your bed clean of weeds, allowing for good air circulation, watering appropriately, and keeping the area free of old plant debris will help.  In very wet years, sometimes it is hard to keep the bed healthy, in spite of your best efforts.  If you must, you can use a copper based organic fungicide to control the disease and not sacrifice your entire strawberry crop.  It is always important to follow the instructions for use and not use the produce any earlier than the recommended time frame.  Just because the copper fungicides are "organic", does not mean that they are safe for humans to consume.

I have very few problems with insect pests in my strawberry bed.  The same cannot be said for bird pests.  Some weeks, I am very fortunate to find a single berry that does not have "bird pecks" in it.  I don't begrudge the robins and the orioles, the cedar waxwings, and assorted other fruit eating birds a few of my berries to share.  But, I do get irritated when they peck holes in every single berry and then leave the rest of it to rot.  To add insult to injury, they then go to my pond to drink and use my furniture there as their own private outdoor bathroom.  Arghhh!!!! 

To deter those little feathered devils, it works best to use bird netting over the entire bed. I place stakes around the bed for the netting to rest upon so that the berries are beyond the reach of the beaks.  Then I stretch two layers of net in different directions.  I've found that a single layer does not deter them - they find a way under it or peck their way through the plastic netting until there is a hole large enough for them to get through.  If they manage to peck their way through the first layer, they usually get caught in between and have to stay there until I take mercy on them and let them free.  In the interim, they raise such a ruckus that it deters other birds from heading that way.  The net gets tacked down with landscape staples to keep them from getting underneath.  It is a pain to have to uncover the bed each time I need to pick berries, but those sweet, juicy, bird-peck free berries are usually worth it! 

Someday, though, I am going to build an enclosed, covered fence around the entire berry patch.   Then I'll sit inside it and laugh at the birds while they are forced to watch the berry juice running down my chin!

Planting Strawberries

Yummy!

Last week we were in a fairly severe drought with high risk of fires from hot, dry and windy conditions.  This week, it is wet and soggy everywhere and many parts of the state are experiencing flooding from the heavy rains of the last few days.  I have a hard time ever complaining about rain, though.  I'm not sure there is such a thing as too much rain in North Dakota - the old saying "Even on its wettest day, North Dakota is only two hot, windy days away from a drought" rings too true.

Unfortunately, I didn't get all my seeds planted before the rain came, but I can live with that because we needed the rain that badly.  Last week, I tilled an area to plant some new strawberry and raspberry starts.  By the time I was done tilling, I think I'd inhaled enough dust to start a garden in my lungs.  Now, my new berries should get a good start with warmer weather and refreshing rain.

Strawberry plantlet formed along stolons

I've grown strawberries for several years but it was time for some new plants.  Strawberry beds need to be reujuvenated every three years or so.  The plants may still look healthy after that time, but they stop producing the quantity and the quality of fruits that they should.  You don't necessarily need to invest in new plants every two years, though.   The new plantlets that form along the stolons or runners can be gently snipped from the parent plant and transplanted to a fresh location. 

When rejuvenating your strawberry beds with the plantlets, you simply take the freed plantlet and set it gently into a soft part of the soil.  There may already be tiny roots forming at the base of the plantlet that can be gently covered with soil, watered in, and left to grow.  If you do not need to move your strawberry bed to a new location, you can simply tap the bottom of the plantlet down into the soil and let them grow.

If you are planting in a new location, starting with the proper conditions will lead to much greater success.  Strawberries need full sun - six to eight hours of bright, direct sunlight each day.  They also require well drained soil.  You should stay away from locations where you've recently grown strawberries, tomatoes, peppers or eggplants, as these all harbor the same diseases that can decimate your strawberry bed.

Choosing a strawberry that does well in your location is also important.  The local University extension services usually have good information as to which varieties have done well in trials for a variety of conditions. 

There are three types of strawberries which bear different quantities and sizes of berries at different times.  Day-neutral varieites are those that don't care about the length of the day and produce fruit and plantlets the entire time that temperatures stay between 35 and 85 degrees.  While they produce for a long period of time, the berries are smaller and fewer than other types of berries.  They will begin producing their first year of planting, which is a real plus for an impatient gardener like me.

Everbearing strawberries aren't really "ever" bearing.  They usually produce a harvest in the spring and then again in the late summer to fall.  The buds they produce in early summer produce fruits in the later summer and fall.  Buds produced in late summer and fall will produce the next season's earliest fruits, so while all strawberries benefit from winter mulching in cold climates, it is a must with these to protect your early crop of the following year.  Even though the plant is hardy to zone 3 in most varieties, that bud that will produce the next season's crops is vulnerable to freeze damage that will keep it from producing the next year.  You may get a small late summer / fall crop from these the first year they are planted, but their most prolific year will be the year after planting.

June-bearing strawberries set their buds in the fall, then produce flowers and fruits for a short time the following spring, usually in the month of June.  They stop producing after that flush of berries and put their energy into producing stolons and plantlets for the rest of the summer.  It is necessary to mulch these in cold climates, also.  June-bearing strawberries generally produce larger berries prolifically for their short production time.  They will usually not produce berries their first year of planting.

Once you've decided on the type of strawberry plants, you'll need to decide which veriety to plant.  Day neutral and everbearing are sometimes used interchangeably.  They are different varieties but are probably close enough in growth and production characteristics that for most gardeners, either term works.  For day-neutral / everbearing strawberries, I've found Mara De Bois,  Evie 2, Tristar, Seascape, Quinalt, Ogalla and Fort Laramie are good strong varieties in my garden.  Of these, Mara De Bois is perhaps my favorite.  The berries are small but the flavor is like an explosion in your mouth - they are sweet, intensely strawberry flavored and scented.  Earliglow, Annapolis, and Honeoye are my best producing june-bearers.

Your new plants will either come potted or bareroot.  They should be planted as early in the spring as possible, in a planting hole wide and deep enough so that the roots can be contained in it without being cramped or bent.  Sometimes bareroot strawberries come with humongous lengths of root - these should be trimmed back to about eight inches or so long.  The roots should be fully covered but the crown of the strawberry plant should be right at the soil surface. 

Strawberries love to crawl along the soil surface, so they need plenty of room to do that.  Plants should be placed about 12 to 15 inches apart in rows that are spaced three to four feet apart.  The strawberry bed will look pretty sparse at first, but given room to sprawl, that is exactly what strawberries will do.

Once they are planted, they need to be watered in well and kept evenly moist.  We'll talk more about caring for your strawberry bed in the next blog installment.

Spring Pond Care

Wiese Acres Pond

I love my pond.  There is nothing quite so relaxing as listening to the water rush over the rocks while watching the fish lazily swim about.  The downside of being a pond owner is that along with ownership comes responsibility for care. 

I don't drain the pond or remove the fish in the fall.  The center of the pond is approximately three feet deep, so the fish go to the bottom and hibernate for the winter.  I pull the main pump and replace it with a small bubbler pump that sets on the perimeter of the deep part of the pond and use a small pond heater to keep an air opening in the ice. 

In the spring, serious pond maintenance is necessary to remove the winter debris and the nutrient load the pond receives from snow melt and spring rain run-off.  I skim all visible debris and algae out of the pond and drain about one-third of the water, then slowly replace the volume with fresh water.  It is important to replace the water at a slow rate to keep from cooling the water too much for the fish and to prevent too high a chlorine content from affecting the fish.  If you have a very high chlorine content in your water, you may need to add a water conditioner to dissipate the chlorine more quickly.  After the pond is refilled, I replace the beneficial bacteria, using the amounts and frequency listed for whatever type of bacteria I am using and start the big pump to begin circulating the water.  

About every other year, I temporarily remove the fish and place them in a large container I've pre-filled with water from the pond.  I place the container in a shady location with a net covering it to protect the fish from predators.  I also remove all the hardy water plants and set them in a bucket of water to keep the foliage and the roots moist.  Then I have my husband drain the pond completely and pressure wash the muck and the algae off the rocks (he gets the really fun job).  When he's all done mucking around in the mess, I add fresh water and beneficial bacteria and let that circulate for a day or so.  Then I move the fish back to their nice, clean home and get set to enjoy my pond. 

I check plants for any signs of decay, clean any old foliage off them, and divide them if necessary.  I insert a pond plant food tablet in the container and gently lower it back into the deep part of the pond.

Each spring, I check the waterfall hose for kinks or leaks, make sure the cord for the pump is intact, and clean the skimmer and filter boxes.  I wash the biological filters well and replace the old pads with new ones to avoid re-introducing non-beneficial bacteria into my cleaned pond.

Doing the proper spring start up care will make it easier to care for the pond the remainder of the season.  Starting with a nice, clean pond and adding beneficial bacteria on a regular basis (just how often depends on the type of bacteria you use) will help keep things in balance in the pond.  Hitting algae blooms with the appropriate algaecide and keeping the right number of fish and plants for the water volume of the pond will help your pond provide far more enjoyment than work.

More Spring Work

Wiese Acres North Yard

This is the only time of year that I kind of wish I didn't live at Wiese Acres.  Just a little bit.  Cleaning the winter debris off the gardens is my least favorite part of gardening, but doing it right is so critical to the success of the gardening season.   I'm taking today off from work at my job to finish up the cleaning work in the gardens so I can start on things I like to do - like planting, dividing, getting the garden decor out, and firing up the water features.

One of the first things I will do after the cleaning is finished is divide any summer or fall blooming perennials that are getting overgrown.  These were marked last fall because I don't always remember when that cute little clump appears in the spring that it had turned into a giant by mid-summer last year.  The rule of thumb is that fall and summer blooming plants are best divided in early spring, and spring blooming plants are best divided in fall.  Daylilies and iris prefer to be divided in August, here in the midwest.

I'll also be preparing the sites to plant my new perennials that are arriving in the mail on an almost daily basis now.  I will "harden" the plants off a bit in the greenhouse before I plant them in the gardens.  We are still having some very cool nights and a hard freeze could damage their tender foliage.  The process of hardening them off a bit more and giving Mother Nature a little extra time to get her spring act together this year will be helpful.  It also will give me a little more time before I need to turn the water on in the irrigation system so there is less worry about a hard freeze damaging the lines.

Newly planted or transplanted perennials need sufficient water, even if they are drought tolerant plants.  No plant is truly drought tolerant until it is well established, usually after the first year or two of growth.  Prior to that, they will require one-half to one inch of water each week.  I'll also spread a layer of compost, topped by organic mulch, around my new plants to keep the moisture more consistent and to keep the roots cooler as the summer heat sets in.

Cleaning and dividing will keep me busy for awhile!

Spring Crocuses

Wiese Acres Dutch Crocus (Crocus Vernus)

It's been a long time coming this year, but I am now sure that spring has arrived - my crocuses are blooming their hearts out.  They are amazing little things - they can get nipped with nasty cold at night, end up buried in snow, or baked in the hot sun of unseasonably warm temperatures, yet they still do their best to put on a marvelous spring show.

Crocuses, or croci (croak-eye), are members of the iris family.  They grow from a corm that is usually planted in the late fall for blooms the following spring.  The crocuses I have in my garden are different than the ones I used to search the pastures on the farm for in the early spring - while we commonly call those wild flowers "crocus",  they are really pasque flowers.  They are similar in flower appearance and in bloom time, but the wild "crocuses" are from the buttercup family and have hairy leaves versus the smooth, blade-like leaves of the true crocus from the iris family.

There are over 80 species of crocus, but most of what we see in the garden centers are a mixture of species and varieties.  Dutch crocus, or Crocus vernus is the most common species we see.  The only thing you really need to pay attention to when buying crocus corms is whether they are spring or fall bloomers.  I'll be talking about the spring bloomers today.

Crocus are low-growing, reaching no more than about six inches tall.  The size of the flower depends on the species, but they all are six petalled, cup-shaped flowers, usually in shades of purple, yellow, and white.  They look their best when they are planted in large groupings or drifts.  They prefer full sun, but since they bloom in early spring when the trees are not yet fully leafed-out, they will do well planted under deciduous trees.  They require well-drained soil to keep the corm from rotting during its dormant times. 

Crocuses put on their spring show, store food in the corm for the next season, and then go dormant in the heat of summer.  They require very little care - give them a drink now and then in spring and fall.  Leave their leaves alone after they finish blooming, no matter how scraggly and tacky they begin to look.  Crocus are like most other bulbs and corms in that they need that foliage growth time after blooming to store the nutrients needed for the next year's flowers.  I cover up the foliage by planting later emerging perennials nearby, such as balloon flower (platycodon) in locations that stay sunny; or hostas in locations that become more shady as the trees leaf out.

Crocuses do not require a lot of fertilizer.  If you have even moderately good garden soil, they likely don't need anything.  If your soil is a little on the poorer side, you can top dress the bulbs with bulb food or bone meal, either right after they finish blooming or in the fall.

Crocus are short lived bulbs so they rarely need to be divided, but may need to be replaced every few years.  It is well worth the little bit of effort these bulbs require to have that tough little harbinger of spring greet you when you look at your spring garden.

Soil Temperatures and Vegetable Seeds

 

Wiese Acres vegetables

It's hard not to get anxious to be out planting the vegetable garden.  I can just about taste the freshly picked lettuce with the sweet cream dressing that Mom always made, or the large, sweet radishes that Dad and I sliced to make radish sandwiches.  But, most seeds are pretty particular about the temperature they want the soil to be before they are planted.  If soil temperatures are too cool, the seeds will lie there and rot before germination has a chance to occur.

Cool season crops generally tolerate planting in soil temperatures between 35 and 40 degrees.  That is pretty early in most locations, but here's the rub with even these crops:  they might germinate and grow in cold soil, but the green part of the plant still will not tolerate air temperatures that are much below freezing, as can often occur in these northern climates well into May.

Lettuce, onions, and parsnips are some of the earliest crops that can be planted.  They will germinate in a minimum soil temperature of 35 degrees, but their optimum germination temperature is well above that at about 70 degrees.

Peas, radishes, spinach, swiss chard, turnips, beets, carrots, leeks,and all the cole crops (broccoli, cabbage, cauliflower, etc.) will germinate at a minimum soil temperature of 40 degrees, but prefer the much warmer 70 degree soils, as well.


Wiese Acres cabbage

The conventional wisdom that potatoes should be planted on Good Friday might work well in some places, but given that potatoes' minimum germination temperature is 45 degrees, most years Good Friday is going to be just a tad bit early.

Warm season crops need soil temperatures of 50 to 60 degrees to germinate before the seed rots.  These include beans, cantaloupe, corn, cucumbers, eggplant, peppers, tomatoes, summer and winter squash, pumpkins, and watermelons.

If you use treated seeds, soil temperatures are not as critical.  If they are anywhere close, the seeds will probably just lie dormant without rotting until the soil warms enough.  For untreated seeds, which is what I prefer, it is well worth the time to actually check the soil temperatures before planting, because untreated seeds can rot very quickly in cold, moist soil.

Soil thermometers can be purchased at any garden center pretty cheaply and they are probably worth the few bucks investment.  Theoretically, any thermometer that can be inserted into the soil to a depth of four to six inches is able to monitor soil temperatures. 

As a rule of thumb, I don't plant anything in my heavy clay soil until at least mid-May and seedlings don't get transplanted until Memorial Day weekend.  That is when I am pretty sure that soil temperatures are going to be adequate to support germination and the likelihood of a hard freeze killing all my baby plants and having to start over is greatly diminished.