How and When to Start Seeds Outdoors
It may be chilly now, but spring will be here before you know it, and along with it comes planting time. Join gardening expert Melissa Strauss to discuss direct sowing seeds in your spring garden.
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The winter days can be long and gray, but preparing for spring planting can bring cheer on the chilliest mornings. I like to start ahead of time and have my seeds and a plan ready to go as soon as that last anticipated frost day passes.
Starting seeds outdoors depends largely on what you’re growing and in what climate. If you live in a cold climate with long, cold winters, you still have quite some time before it’s a possibility. If you’re in a warm climate like me, you may only be a few short months from planting time. Knowing when and how to get started with your outdoor planting can make or break your growing season.
If you start too early, your seedlings may die in a late cold snap. If you wait too long, you may miss out on prime growing time and end up with cool-weather crops that burn up before they ripen. Let’s talk a bit about when and how to do your outdoor seed starting to get you off on the right foot.
When to Get Started
Your climate has as much to do with planting time as the seeds you plan to start. Since we are talking about starting them outdoors, I want to focus on those seeds that grow best when you sow them directly in the garden. This is particularly important for plants with a tap root, as these often get damaged when transplanted.
In warm climates like Zones 8 and higher, you want to get those seeds into the soil as early as possible. The summer heat will sneak up sooner than you expect some years and can drastically shorten your growing season for spring veggies. In colder climates, it’s important to pay attention to your last frost date, as this will typically dictate your planting dates.
The average last day of frost (32°F/0°C or less) is the first day in spring on which there is less than a 50% chance of frost. To determine your last frost date, use this frost date calculator from the National Gardening Association. For the most accurate local information, call your local independent garden center or your local Cooperative Extension. At the same time, you may want to ask about the average date of the first fall frost for late summer and fall planting.
Research What Grows in Your Climate
The first thing you’ll want to do is figure out what you’re planting. Some plants will grow in just about any North American climate, while others have a more limited range. You can waste a lot of time and money trying to grow corn in Zone 3.
The growing season simply isn’t long enough for some things to develop properly. Likewise, some need cooler weather and will burn up before they ripen in Zones 10-12. The good news is that most annual vegetables will grow in Zones 2-11, which encompasses most of the continent.
Other considerations to make are the soil in your space and the humidity. It’s tough to grow strawberries in arid climates. Some plants just need more moisture than others.
Seed packets usually indicate growing zones. However, few indicate whether those plants need extra humidity. If you live in an area with higher or lower-than-average humidity, it’s a good idea to look into this.
Select Your Seeds
This is the fun part. I love to go seed shopping and see all the interesting varieties available. Do you prefer purple carrots to orange ones? Try ‘Cosmic Purple’ carrots this year. Why not stick with the violet theme and plant some ‘Trionfo Violetto’ pole beans?
Choose the right plants for the season. Some vegetables are better planted in late summer for cool, fall growing. For spring planting, make sure you buy those that are good for growing in the spring.
Collect Your Supplies
A convenient benefit of direct sowing seeds in your outdoor garden is that you don’t need much in the way of seed-starting supplies. Not all seeds grow well this way, so you may still have to start some things indoors, but direct sowing is less work in general.
You’ll need to purchase or acquire any amendments needed to enrich your soil. Make sure you have irrigation set up to keep the soil moist while your seeds are germinating. Watering every day can be labor-intensive without soaker hoses or sprinklers.
If you live in an area with poor or compacted soil, consider planting in a raised bed. It’s far easier to control your soil this way and is less work overall. Metal raised beds have a long lifespan, so if you’re a veteran gardener, they are well worth the investment. If this is your first year, and you’re not sure whether you’ll continue on, wooden beds will last a year or two.
If you want to make things easier on yourself throughout the season, weed cloth is a great tool. Laying this down between rows or over the entire bed can really cut back on weeding. Mulch to top things off after your seedlings sprout will also suppress weeds and help maintain moisture in the soil.
Prepare Your Beds
Once you have all the materials needed, prepare your beds for planting. If you have great soil already, you may be able to simply loosen it up and remove any weeds. For most of us, amending the soil is part of spring planting.
Either way, planting requires some prep work, and it should happen ahead of time to give your seeds the best chance at growing strong and productive. Loose earth is important, as it supports the growth of fine, young roots. A soil test is a great tool as well to find out the composition and pH of the earth in your garden.
Loosen up the dirt in your beds. If your soil is sandy or poor, mix in plenty of organic material like worm castings, manure, and compost. For heavy clay that compacts easily, mix in materials with large particles or those that improve drainage, like coarse sand and peat moss.
If you’re planting in raised beds, depending on their height, it can be costly to fill them completely with garden soil. You can fill the bottom with tall beds with leaves, branches, and other yard materials that are clean and free of pests or diseases.
Many spring vegetables and other plants are heavy feeders. It’s a great idea to mix some fertilizer in before planting to give them a strong start. Initially, most plants need high nitrogen to get started. A lower nitrogen formula better serves root vegetables with higher potassium and phosphorus.
Prepare Your Seeds
Many seeds are fine for dropping in the ground with little to no preparation. Others germinate faster if you do some prep work. Those with soft or thin outer coverings don’t require soaking, but some need cold stratification. If your seeds require stratification, make sure to do this well ahead of time so you don’t end up with a lousy germination rate.
Those with tough outer coatings or shells often need a bit of preparation. All seeds need water for germination, and more delicate seeds take in that moisture quickly. Soaking tougher ones overnight will start the process. Scarification is helpful for some with tougher coatings, like beans and peas. Adding some liquid fertilizer to the water is helpful as well, but it is optional.
Follow the Instructions for Planting Depth and Soil Temperature
After prepping your beds to start seeds outdoors, find out what soil temperature they each need for germination. Some can sprout in cold earth that’s barely workable, while others need it to warm up to about 65°F (18°C). Make this determination before you soak anything.
For plants that are frost tolerant, you can often plant several weeks before your final anticipated frost date. Most spring plants are not frost tolerant, so you should wait until that date has definitely passed.
In addition to temperature, it’s important to determine which seeds need light to germinate and which need darkness. This dictates the depth at which you plant them. Those that need light should be surface sown or gently pressed into the soil. Some need only a light covering of soil. Others need to go in holes up to an inch deep so they aren’t exposed to light until they sprout.
Offer Protection or Support if Needed
Growing plants like beans, peas, corn, tomatoes, and many others often requires support. Tomato cages, trellises, and other supports should be in place before they are necessary. Waiting until your tomatoes are in full swing makes it much harder to fit a cage down over the plant without breaking stems.
Some delicate vegetable plants and flowers also need protection from the wind or support to keep them from toppling over. I grow a considerable number of flowers for cutting. Many of these have long, slender stems, which are great for floral arrangements but vulnerable to the elements. Be ready to stake these types of plants as soon as they need support.
Maintain the Correct Moisture Level
Once outdoor seeds are in the ground, it’s important to start irrigating. Maintaining the correct moisture level in the soil is crucial. Seeds can’t germinate in dry soil, and seedlings don’t retain much moisture, so they need consistent watering.
Don’t overdo it on watering, either, as many root systems are vulnerable to rotting. This is especially true when they are young and delicate. You want to keep the soil moist but not waterlogged. Once your seedlings sprout, a thin layer of straw will help retain moisture in the soil and cut back on your effort level.
I like soaker hoses for keeping my beds watered, particularly in the early stages when daily watering is important. I keep them on a timer, and the water soaks directly into the soil. Sprinklers work, but you can lose a lot of water to evaporation. Drip irrigation is also an ideal way to water your beds.
Be Patient
Now, the waiting game begins. Your seeds won’t all germinate at the same rate. Many seed packages will give you an idea of how long germination takes, while others will omit this information. You may see some sprouts pop up within the week.
I’ve often planted things and resigned myself to a poor germination rate, only to see them pop up after several weeks to a month. Ranunculus and dahlias can take a surprisingly long time to sprout. Just try to be patient and let nature run its course.
Alternative Method – Growing in an Unheated Structure
As an alternative to direct sowing seeds that still keeps your starting materials outdoors, you can start your plants in an unheated structure in many climates. A greenhouse, cold frame, or tunnel is great in milder climates. Basically, give them just enough protection that they can germinate and not get knocked out by a late frost.
This will enable you to start your plants a while ahead of time and not have trays all over the house. This method is not effective for those who need direct sowing for root integrity, but it is effective for many.
