Prepare Clay Soil for Spring Planting

One of the major considerations when putting in a new garden is soil texture. The mineral make up of soil is a mixture of different sized particles: sand, silt and clay. Each component plays an important role in the soil’s structure, impacting how well roots can grow and how much water and nutrients are available. The goal is to find a good balance.

Ideally your garden’s soil will contain at least 20% clay. Soil with over 35% clay is considered “clay soil.”

Clay soil hold a lot of water (up to eight times as much as sandy soil) and are slow to dry out. This is an advantage in times of drought, but in wet climates it means they get waterlogged easily. Wet clay soils tend to be cold and slow to warm up in spring. It’s no wonder that many plants don’t over-winter well in clay soils.

Additionally, most plant roots have a hard time penetrating clay soil. The pores are so small and the particles so densely packed that plants will struggle to grow and thrive.

If your garden has clay soil, don’t give up hope. Clay soils can be heavy and difficult to work with, but if you persevere they can be very fertile and productive.

Use the tips below to turn your clay soil into an environment your plants and other beneficial organisms will love.

Blue spade in garden bed. Photo source: Markus Spiske, UnsplashTiming is everything
Limit cultivation to times when soil is not too dry or wet. If you work with dry clay soil it will be so hard it is almost impossible to dig and may crack into large chunks that crumble to dust. When this dust gets wet it sets rock hard, almost like plaster. It’s usually pretty obvious when it’s too dry to work with, and you may need to add water via irrigation, or wait for a soaking rain to soften the ground.

While working with dry clay soil is difficult, cultivation of wet clay is even worse. Wet clay soil compacts very easily when you put any pressure on it, creating a sticky mass that is also hard to penetrate. One sign your soil is too wet is when you leave shiny footprints where you’ve walked because the water has been squeezed from the soil.

Amending clay soil
Add well-decomposed organic matter like compost to help particles cluster together and form larger aggregates. This will improve drainage and aeration.

You can improve clay soil’s structure by adding a mix of 80% gypsum and 20% dolomitic lime. Use an ounce of this mix per square foot of soil in spring and again in fall. This may be repeated for a second year, while also adding as much organic matter as possible.

Adding calcium may be useful to improve soil structure temporarily, until you can get sufficient organic matter and soil life into the soil. But this only works if the soil is low in calcium.

Be sure to double dig to thoroughly incorporate organic matter and calcium, as well as fertilizer and other minerals your soil may need.

Garden fork and shovel in grassLong-term solutions
Use green manures to improve structure. Growing a green manure crop will protect the soil surface as well as add organic matter when you dig it in at the end of its season.

In autumn, when it’s relatively dry, roughly dig the soil and leave it over the winter for frost to break down the large clumps.

Other suggestions for working with clay soil
Use raised beds to improve aeration and prevent future compaction. Build them high to help them drain and warm up.

Slope the site slightly so the soil can drain more quickly.

Never allow clay soil to get so dry that is cracks. These cracks increase evaporation and make the soil hard to re-wet because water simply drains away down the cracks. If it does dry out, cultivate the soil surface.

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The trick to a successful first garden: start out small

You might not think so from the countless words that have been written about it, but vegetable gardening is a pretty simple process. Plants are genetically programmed to grow (even our pampered crop plants) and all you have to do is give them the right things at the right times. You take seed, put it in the soil and it grows. The basic requirements are soil, sunlight, seed, water and motivation. Continue reading “The trick to a successful first garden: start out small”

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Ask a Gardener: finding your frost dates

This is another post in our Ask a Gardener series where you get to ask our resident experts your gardening questions. Send your questions to gardener@smartgardener.com.

Image: frost of leaves and grass; Source: Chandana Ban, Unsplash

Becky D. asks:
I don’t know my frost dates. How can I find that information?

Why it’s important
Gardeners need to know the date of the average last frost in spring and the average first frost in fall because these are used to determine planting dates. The last frost date in spring is a good general guide about when it’s safe to put out plants.

Smart Gardener uses your zip code to automatically determine your frost dates, which works very well if you live in an area with a fairly uniform climate. But if the area covered by your zip code is very diverse (my zip code starts at sea level and goes up to 2500 ft and actually contains more than one climate zone), this may not be an accurate guide for planting, which is why we have included the option to adjust your frost dates in your profile to more accurately reflect your conditions.

In my case, my zip code spring frost date is based on Santa Cruz, which is nearly a month earlier than my actual date. Knowing the frost dates vary dramatically in my area, I looked for more specific information for the area where my garden is located.

Check your local climate center
If you’re in the United States, your best bet is to check the NOAA website for a link to your local Regional Climate Center. I found the Western Regional Climate Center website to be very helpful. My area is covered by the Northern California climate summaries map. This map showed my closest weather station to be in Ben Lomond, so I clicked on that page.

Ben Lomond California Regional Temperature Chart

On the left of the page under Temperatures I found Spring ‘Freeze’ Probabilities. This brings up a graph showing the probability of the occurrence of various temperatures around freezing. Where the orange (32 degree F) line bisects 50% is the average last frost date, which for Ben Lomond I estimated to be about the 23rd of March.

The first fall frost date is also found under Temperatures as Fall ‘Freeze’ Probabilities, and has a similar orange (32 degree) line. Where this bisects 50% is the average first fall frost date. I estimate this to be about the 12th of November for Ben Lomond.

There is also a ‘Freeze Free” Probabilities page, which has a graph showing the length of your frost free season. For Ben Lomond I estimate this to be about 240 days.

Smart Gardener Frost Date Settings

Editing your garden planner
Once you know your average last frost date, you can enter that manually in your garden’s settings in the Smart Gardener app. Next to your garden’s name at the top, select “Settings.” Under “Growing Season Settings” you can edit your first and last frost dates based on what you learned from your Regional Climate Center’s information.

Smart Gardener will use these updated dates to determine your best dates for planting the vegetables you selected for your garden, guiding you on when to start your seeds and when to transplant your seedlings outside.

Things can change
It’s sometimes said, “Climate is what you expect, and weather is what you get.” Keep in mind that these frost dates are averages and so of course they will vary from year to year (some years it will be earlier and some years it will be later).

But following the info above will give you a good idea of how to determine your garden’s last spring frost date and first fall frost date, and that will be a good place to start.

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Peas for St. Patrick’s Day

Image: Peasl Photo source: Jessica Ruscello, UnsplashIn Ireland, St. Patrick’s Day is the traditional day to plant peas in a spring garden. In the United States the timing can vary somewhat from zone to zone, but March 17th still works well as a guide for starting peas for most areas. And what a perfect way to bring your garden a bit of the “luck of the Irish” by planting something green!

Why you should grow peas.

Did you know peas have been cultivated by humans for anywhere from 8,000 to 12,000 years? Peas are an easy, rewarding crop for spring, and are a great way to fix nitrogen in the soil for your summer plants. As an early spring crop they can be out of the ground by June, leaving time for a warm weather crop to succeed them.

Selecting a variety.

Image of peas in a basket

Dried Shelling Peas are typically used for soups or stews, and fresh shelled immature peas are good lightly steamed or boiled. Their pod is too fibrous to be edible, and the peas themselves must be removed from the shells, hence their name. Bush Shelling peas grow in a compact bush form, while the more common Vine Shelling peas, which grow on vines that require staking or trellising but which are generally more productive than bush varieties.

Snap Peas are a more recently developed edible-podded pea, this one originated in America. The pod is thicker and more succulent than that of the Snow Pea, and less fibrous than standard Shelling Peas. These are now one of the most popular types of pea, because there is no work in shelling and very little waste.

Snow Peas have thin crisp pods that are nearly translucent and bright green, with tiny seeds. The whole pod is edible and quite sweet when picked at the right time. The name may come from the whitish tint reflected from the pods, or because of their tendency to grow at the end of winter, just before the last spring freeze. As their name suggests, they can be covered with snow during these times, but still keep growing.

When to plant.

In moderate climates, you can sow directly into your garden bed, while in colder climates you may need to start them indoors. Fortunately, peas do well in containers, so you may not even need to transplant them!

In warmer climates, you may have already started your peas back in January or February, but you can still continue to sow new seeds for a second harvest before the warm days of summer.

Getting started.

The best soil for peas is a loose well-drained loam. Peas don’t need a lot of nitrogen, as they can obtain their own. In fact, if nitrogen is too easily available they won’t bother to fix any. Peas do need phosphorus (colloidal phosphate) and potassium (wood ashes), as well as calcium and magnesium (use dolomitic limestone).

If the soil is compacted double digging is beneficial. If it is poorly drained, use raised beds, especially for early plantings, as they don’t like wet soil. In very poor soils it may pay to plant your peas in trenches, filled with a mixture of soil and compost.

If you’re growing a vining variety, you will need to supply a trellis or poles for the plants to grow along.

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Don’t feed the birds

There are few things more frustrating than preparing, planting and pampering a bed of peas or beans and then discovering that the newly germinated seedlings have all been wiped out by birds.

In most places birds are only a significant problem in spring when they seem to relish the abundant succulent green seedlings, but in my garden quail can be a problem anytime. In winter they go for the Brassicas, in summer they like any succulent greens, and in fall they eat newly sown, or emerging, cover crops. I’ve learned the hard way if I leave a seedbed unprotected I am pretty much wasting my time, as I will be lucky to harvest anything from it.

Tips on how to protect your plants:

Easy: The easiest method to keep birds away is to use scare tactics such as flashing tape, hanging old CDs, scarecrows, and predator balloons. The problem with these is that birds will eventually get used to them and start to ignore them, though they may work long enough for your planting to grow out of its most vulnerable stage.

Functional: The usual solution to serious bird predation is plastic netting. This is awkward to handle and put up (it’s an extra step after planting that you don’t need), and somewhat hazardous to wildlife (I have released several tangled snakes) but in these circumstances it is a necessary evil. I usually support the netting on hoops made from lengths of discarded ½” polyethylene irrigation pipe, weighted down at the edges with wood or soil. It’s not particularly elegant, but its quick and it works.

Extreme: In the most extreme cases you might decide to cage the whole garden (especially if you are also plagued by rabbits, deer, squirrels, or raccoons). The simplest and cheapest way to do this is to put an 8 foot tall chicken wire fence around the garden and make a roof out of plastic bird netting.

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Spring Vegetables

Image of seedlings in pots. Photo Source: Francesco Gallarotti, UnsplashSo you’ve got your soil ready, it’s finally warm enough, and now you’re thinking about what to plant. It’s tempting to start planting all those great seeds you bought over the winter, but it’s best to take a moment and consider what weather conditions each plant needs to germinate and thrive. Each plant has an appropriate time to be planted, and it’s important to be aware of which plants can go out at what time.

The vegetables that grow well in spring all originated in temperate climates and prefer cool (50-75˚ F) growing conditions. When you first plant your spring crops, the soil and air are cool and days are fairly short, so crops germinate and grow slowly. As spring progresses the days lengthen and the weather gradually warms, until by the time most crops are ready to harvest it may be warm most of the time. Fall has cool weather too, but there the reverse is true, conditions are warm for seed germination and growth (and pest activity), while maturation takes place in cooler weather.

When to plant
Blue spade in garden bed. Photo source: Markus Spiske, UnsplashIt is important to get your spring crops into the ground as early as possible, so they have enough time to grow and mature before the long, warm days of early summer cause them to bolt or develop bitter or pungent flavors. Fortunately cool weather crops aren’t perturbed by minor cold snaps, so planting them early isn’t a big problem. If it is cold they will just sit and wait until the weather warms up enough for growth.

The hardiest crops can be planted as soon as the ground is suitable for making beds in spring, which may be 4 to 8 weeks before the last frost date. These plants include: leek, onion, parsley, pea, spinach, and shallot.

The slightly less hardy crops can be sown 2 to 4 weeks before the last frost date. These include: lettuce, cilantro, mustard, and radish.

The rest of the spring crops are sown a couple of weeks before last frost date. These include: beet, carrot, broccoli, cabbage, chard, kale, and potato.

 

Smart Gardener makes it easy
We show you quickly and easily when it’s the right time to start your seeds indoors or outdoors, based on your region. Just check the Overview tab in the variety descriptions, and you’ll see when to start your seeds, transplant your starts, and harvest your vegetables. The top lines are for spring/summer crops, and the bottom lines are for fall/winter. Easy as can be!

Planting Overview showing sowing guide

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