What to Grow When
June 7, 2020
How do you know what to grow when? It's a great question for beginning gardening to know and more advanced gardeners re-remember! Knowing your 1) hardiness zone (how cold it gets), 2) the first and last frost dates, 3) how much sunlight you get in your backyard and 4) your general soil type/conditions, will give you confidence on what will thrive in the garden. Knowing the basics also helps one lean creatively into working with your limits as well as help to shrug off "failures" as learning experiences.
1). What is your hardiness zone? What are the coldest temperatures you get in your region in winter? This is often referred to in the US as your hardiness zone. Check out the USDA map here to figure out yours. As I write, I am in Philadelphia, Pennsylvania and my hardiness zone is 7a, meaning the lowest temperatures I can expect in the winter are between 0 and 5 degrees Fahrenheit. If I am choosing trees, shrubs, vines, or any plants that come back each year, I want to make sure they are hardy or can handle the temperatures in zone 7. I might be able to get away with less hardy plants (zones 8 and up), but only if I plan to protect these more tender plantings somehow in the winter by bringing them inside to bright sunny space in winter or using a greenhouses... it's possible, but labor intensive. Though many varieties now exist that are easily accessible and adapted to different climates like zone 4 peaches ('Contender' and 'Reliance') and hardy figs to zones 6 or even 5 with protection ('Brown Turkey' and 'Hardy Chicago').
The hardy "Reliance" peach growing on my 3rd floor balcony garden. Fresh, homegrown peaches are truly the best!
Does that mean if you are in the south you can grow anything from up north with a hardier zone? Not necessarily. Many of these plants that survive well in lower hardiness zones also require 'chill hours.' Chill hours are hours accumulated with temperatures between 30-45 degrees F that the plant "needs" in order to trigger flowering. Apples and blueberries, for instance, often need a lot of chill hours before they will be induced to flower. Some apple and blueberry varieties do exist that can be grown farther south like the 'Anna' apple for zones 6-8 or the rabbiteye blueberry (Vaccinium ashei) for zones 7-9.
Many wildflower seeds need a certain # of chill hours just to sprout. Lanceleaf Coreopsis (above) needs 30 days worth of chill hours. To get your chill hours, plant seeds in the fall or very early spring OR put them in the refrigerator in a moist coffee filter for 30 days to induce a "winter" before planting in spring!
2). Know your first and last frost dates. Determine the last approximate frost date is in the spring and the date of the first frost expected for your area in the fall. A quick google of "First and Last Frost date for (insert name of your city)" should bring up exactly what you need. This will help determine your growing season! My growing season from about April 5th through November 11th is a little over 7 months which is enough warm weather to grow most of my garden favorites, and creatively plan for winter growing.
When starting plants ahead of time from seed, often you will see reference to starting some weeks before or after the last frost date in spring or however many weeks before first frost date in fall. Even experienced gardeners can use a refresher as first and last frost dates are beginning to shift every couple of years.
Tomato seedlings prefer warm soils. They will not thrive or get ahead if you plant them too early in cold spring soils... however tempting that might be! They will grow better, faster, stronger if you wait for the soils to warm up!
You'd think hardiness zones and frost dates would somehow correlate to each other: low hardiness zone, so short growing season? Right? Not necessarily! If I live in a climate with a very mild winter such as mountainous northern California, my main growing season could be quite short as in the last frost could be the beginning of June (!!) and first frost date might be as early as mid-September(!!) Yikes! That a scant 4 month season without a danger of a frost! It might sound like a limit, but it is really an opportunity to work creatively with your limits! Singing Frogs Farm has the climate I just described, yet they don't allow it to stop them from being leaders in generating an incredible amount of revenue per acre from their ingenious planting and soil-building strategies!
Did you know cilantro (despite its use in hot salsa recipes!), is actually a tender spring green that thrives in cool weather after danger of a frost has passed!
3). Know your sunlight levels. Do you have full sun, partial sun, or shade? I think of full sun as being at least 6 hours of sun per day. Plants that LOVE full sun are big tomatoes, zucchini, basil, sunflowers, melons, corn, blackberries and many meadow flowers, just to name few! I usually consider partial sun or partial shade to be less than 6 hours. Many crops still thrive in these cooler conditions like woodland berries as well as lettuces, greens, scallions, and radish. Some plants can also thrive in the shade like ferns, ramps, currants, gooseberry, and countless shade tolerant flowers like trout lily, bloodroot, and wild ginger!
Hazelnuts are shrubs that can thrive in the understory, shaded beneath canopy trees! Yet they will produce more nuts if they have full sun. This is true for many woodland berries and nuts which can handle quite a bit of shade yet will produce more the more sun they receive.
Think of your leaves as little solar panels. Radishes do grow well in part shade conditions yet they will take longer to "bulk up" or get enough "solar charge" to produce the sugars needed to make that tasty root.
If you find yourself with less sun than you'd like, manage your expectations. Find the strengths of what you have to maximize the success of your garden. Less than six hours of sun? Well, if you really want to grow those tomatoes, plant cherry tomatoes instead of full sized slicers for better chances of success. Or consider that you might actually be able to grow cooler season crops with lower light like lettuce, greens and dill all season long instead of just in spring or fall!
Cool weather crops: Crops like lettuces, spinach, spring radishes, and arugula LOVE cool weather. Once it gets too hot in summer, they will "bolt" or stopping producing and go to flower/seed. Shadier gardens have a unique advantage here as can often get away with growing these cool weather crops much longer into the summer.
TIP: Sunlight planning: Finding the BEST SPOT for your garden! You can use a compass to make an educated guess or one option I like is to use a sun tracking app to count how many hours of sunlight I get through the day. The one I currently use is called "Sun Seeker", it is inexpensive, and has a good "3-D view" (pictured below) where you can literally count the hours throughout the day and compare it to different seasons in the year! Definitely recommend it (or something like it) if sunlight at your site is complicated... as many urban sites are.
4. Know your soil conditions. Wet or dry? Sand, silt or clay? When establishing trees, shrubs, vines and perennials (plants that return year after year without needing to be replanted), different plants prefer or tolerate a different range of conditions. For example, 'Swamp Milkweed' with it's rose-pink, fragrant flowers tolerates wet soils (think near the edge of swamps), but can also do just fine in well-drained soils. While Butterfly Milkweed (bright orange flowers) prefers drier, sandier soils and even can handle drought. Each plant, in some sense, has a personality, and it is up to you to know your site (wet or dry? sand or clay? compacted or aerated?) to help get the right plants for your conditions. Once you know your conditions, seed companies, nurseries and garden centers can more easily recommend varieties that will do well!
What is the difference between sand, silt and clay? The easiest way to describe it is particle size. Bigger particles that make up sand behave one way: faster draining, more aerated soils, easier to dry out, and less able onto hold nutrients. Clay soils, on the other hand, have the smallest particles which behave entirely differently: slow draining, good at holding onto nutrients (sometimes too tightly!), overlapping and interlocking particles can form a compaction layer or oxygen-less environments that make it hard for roots to "breathe". Equal mixes of sand, silt and clay creates a magical combination with the benefits of each and referred to as loam! If you don't have perfect loamy soil, don't despair! You can materials to lighten clay-rich soils like sand, expanded shale, biochar, and compost, as well as add things to "tighten" sand-rich soils like rock dusts, clay or clay minerals, compost or biochar. Soil biology and organic matter are also instrumental in creating structure, pore spaces and enhancing nutrient retention in less-than-ideal soils!
SUMMARY: If you know your hardiness zone (how cold it gets), the first and last frost dates, approximately how much sunlight you get in your backyard, your general soil type/conditions, and what conditons your plants prefer, get ready for a great gardening season! You've got this!
Resources:
USDA Hardiness Zone Map: https://planthardiness.ars.usda.gov/pages/view-maps
Singing Frogs Farm in Northern CA: https://www.singingfrogsfarm.com/