When To Start Your Garden: 2021 Planting Calendar

December 15, 2020

Introduction: Timing Is Everything

When To Start Your Garden
hands planting a tree

An outdoor space that’s packed with colorful, vibrant flowers and delicious homegrown produce all summer long is every gardener’s dream. However, getting your garden to this state of nirvana takes a lot of patience, care, and, most importantly, it needs to be planned well in advance. 

The best way to get your garden looking full and healthy for a glorious summer display is by creating a planting calendar. But what is this exactly? And where do you even begin when it comes to creating a planting calendar? 

We’re here to give you all the help you need! Below, you’ll find information on creating your planting calendar, the importance of factoring in frost dates, and some handy tips on how to get started. We’ve even included some useful information on some problems you may encounter, and how to prevent these issues from occurring. 

What Is A Planting Calendar?

2. What Is A Planting Calendar

Let’s get things started by taking a look at what a planting calendar is. Put simply, a planting calendar is a guide to what seed to sow and when to sow it. It will also give you an indication of when it’s safe to transplant delicate seedlings outdoors to their final positions.

When you’re designing your planting calendar, it’s a good idea to separate plants into two different categories - ornamental and kitchen garden. By doing this, you’ll be able to organize the different areas of your garden better. You’ll also be able to ensure that you’ve got a good crop rotation process in your vegetable garden. 

A planting calendar isn’t only about seedlings, though. Some ornamental plants are extremely tender and cannot be left in the ground over winter. Even a single touch of frost could kill them straight down to the root, and we all know there’s no recovery from that! 

With this in mind, your ornamental planting calendar should also tell you when it’s time to dig up your tender perennials and move them into a sheltered, frost-free area. We’ll take an in-depth look at frost dates a little later on to explain this in more detail. 

There are many different ways you can design your planting calendar, but the most important thing is that it clearly tells you what plant you can sow indoors or outdoors depending on your area’s frost dates. To make things a little easier, and to give you a better idea of how to create a planting calendar, we’ve put together a sample guide below.

Sow Indoors

What to Sow

Number of Weeks Before Last Frost Date

Earliest Date to Transplant Seedling Outdoors


5 weeks 

1 week after the last frost date


6-8 weeks

2 weeks before the last frost date


8-10 weeks

4 weeks before the last frost date


6-8 weeks

2 weeks before the last frost date


2-3 weeks

2 weeks after the last frost date


6-8 weeks

3 weeks after the last frost date


8-10 weeks

4 weeks before the last frost date


7-8 weeks

3 weeks before the last frost date


1-2 weeks

2 weeks after the last frost date


10-12 weeks

4 weeks before the last frost date


10-12 weeks

2-3 weeks before the last frost date


6 weeks

2 weeks after the last frost date


1-2 weeks

2 weeks after the last frost date


1-2 weeks

2 weeks after the last frost date

Swiss Chard

6-8 weeks

2 weeks before the last frost date


6-8 weeks

1 week after the last frost date

Sow Outdoors

What to Sow

Earliest Direct Sowing Date


On the last frost date


1 week after the last frost date


3 weeks before the last frost date


2 weeks before the last frost date


2 weeks before the last frost date


On the last frost date


2 weeks after the last frost date


1 week before the last frost date


4 weeks before the last frost date


2 weeks after the last frost date


6 weeks before the last frost date


2 weeks after the last frost date


4 weeks before the last frost date


4 weeks before the last frost date

Swiss Chard

1 week before the last frost date


2 weeks after the last frost date

You can use a spare diary to create a planting calendar. This is particularly useful if you tend to have more time on the weekends as you can plan certain tasks over set days, rather than using the entire month as a reference point. 

When you’re designing your planting calendar, it’s important to give special attention to whether you can sow seeds directly in the ground or if they need to be started off undercover. You’ll be able to find this information on the seed packet. 

Knowing Your Frost Dates

3. Knowing Your Frost Dates

As we’ve mentioned above, some seedlings and plants are susceptible to frost damage and some are even so tender that frost-exposure could kill them off altogether. Seedlings are also highly likely to be killed off by frost. 

This isn’t only heartbreaking after putting so much effort into raising them, but can also throw your planting calendar off by several weeks and really put you behind schedule. You may even miss out on the growing season altogether.

To prevent any frost damage on perennial ornamental plants, annual seedlings, or kitchen garden plants, it’s important to know your frost dates. These dates can vary quite dramatically between states, and in some places, patches of frost can occur over a six-month period. 

When it comes to frost dates, the United States is broken down into different regions, ranging in number from 3-10 that run in ascending order from the top to the bottom of the country.

Regions that are lower in number are more susceptible to frost and for longer periods, while regions that are higher in number will be less likely to see frost. And, if they do, it won’t stick around for very long. 

So. Before you even begin thinking about creating your planting calendar or sowing your first batch of seeds, make sure you know what the frost dates are in your region. Below, we’ve put together a handy guide that will show you the average frost dates in your region.

Zone 3

  • Average First Frost Date: September 1st - September 30th
  • Average Last Frost Date: May 1st - May 31st 

Zone 4

  • Average First Frost Date: September 1st - September 30th
  • Average Last Frost Date: May 1st - May 31st

Zone 5

  • Average First Frost Date: September 30th - October 30th
  • Average Last Frost Date: March 30th - April 30th

Zone 6

  • Average First Frost Date: September 30th - October 30th
  • Average Last Frost Date: March 30th - April 30th

Zone 7

  • Average First Frost Date: September 30th - October 30th
  • Average Last Frost Date: March 30th - April 30th

Zone 8

  • Average First Frost Date: October 30th - November 30th
  • Average Last Frost Date: February 22nd - March 30th

Zone 9

  • Average First Frost Date: November 30th - December 30th
  • Average Last Frost Date: January 30th - February 28th

Zone 10

  • Average First Frost Date: November 30th - December 30th
  • Average Last Frost Date: January 15th - January 30th

By working out your first dates ahead of planting, you’ll be giving your seedlings a much better chance of survival and helping them grow into strong, healthy plants that will provide you with a bounty of crops.

Getting Started: Pre-Planting Tips

4. Getting Started Pre-planting Tips

As you can probably tell by now, organization is key when it comes to sowing seeds and planning your garden. It’s not all about knowing what to do and when to do it, though. You’ll also need to make sure that all of your equipment is organized and ready to go when the time comes to use it. 

Sort Your Packets

Try and keep your seed packets as organized as possible. This will make it easier to find the correct seeds for the task at hand. 

A seed-storage box is a fantastic tool for this as you’ll be able to keep everything together in one place. 

It’s also a good idea to sort your packets of seeds into different groups, and there are a couple of ways you can categorize them. The first is to keep the same type of seeds together. 

So, for example, if you have several varieties of tomato seed that you’d like to try growing, bunch all of those seed packets together and secure with a rubber band to create a single group. 

1. Sort your Packets

You can also organize your seed packets by sorting them into monthly groups inline with your planting calendar. This gives you the opportunity to work through each different packet one by one and plant them when it’s appropriate to do so. 

Again, bunch them into one group and secure them together using a rubber band. Then, write the month they need to be sown on a piece of paper and use this to label the collection of seeds. 

When you start sorting your seeds into groups, it’s also important to pay attention to the expiry date displayed on the packet. A packet of seeds that has gone past its expiry date is unlikely to germinate, so you’ll just be wasting your time and effort by trying to raise a seed that just won’t grow. 

Think about the storage environment for your seeds too. They need to be kept in a cool, dry place. Storing them anywhere that’s hot or humid, or where the packets could get wet, may cause the seeds to rot. In some cases, they might even start germinating inside their packets, which could completely throw your planting calendar off course!

Equipment You’ll Need

Seeds are an imperative part of starting your garden, but you’ll also need some equipment to help you raise them into healthy seedlings that will grow into strong plants. 

Gardening Tools

2. Gardening Tools

You’ll need a wide variety of gardening tools to help you create your garden too, and each of these will be specific to a certain part of your seedling’s growth.

Below, you’ll find a list of some of the most essential gardening tools along with a brief explanation of what it’s used for:

  • Dibber: This is a gardening tool with two purposes. 

The first is to create small holes in the soil in which to place your seeds. Some dibbers come with measuring guides engraved on them, and these are particularly useful for getting the sowing depth correct. Secondly, a dibber can be used to gently coax the seedling out of the seed tray and transplant it to its own pot or straight into your garden’s soil.

  • Trowel & Spade: A trowel is essentially a small spade that can be used for transplanting well-established seedlings and smaller plants straight into the soil. A larger spade will need to be used for creating particularly large holes, and for digging up any annual plants that have died back in fall or winter.
  • Fork: Garden forks are available in two sizes. The smaller, handheld garden forks are ideal for gently removing larger seedlings from their trays without causing much damage to the delicate root systems. Larger forks are great for preparing and working compost into the soil you’ll be planting your seedlings into.
  • Snippers/Secateurs: As some plants begin to mature, it’s important to remove certain parts to keep the structure of the plant strong and to ensure a high yield of crops. Tomatoes, for example, need to have their side shoots removed in order to concentrate more of their energy on creating fruits. The best tool for removing any parts of a plant are snippers or secateurs. This will create a clean cut that will be less susceptible to disease.

Seed Trays

The best way to sow seeds is to scatter them into a seed tray that has been filled with compost. There isn’t a guarantee that all the seeds you plant will germinate, so by doing this rather than planting each seed into its own pot, you’ll be saving yourself time and taking up a lot less space. 

Seed trays come in a huge variety of shapes and sizes, but the most important thing to look for is drainage holes. If a seed tray doesn’t allow water to pass through it, the seeds you’ve sown are at a higher risk of sitting in stagnant water and rotting. 

If you’re particularly environmentally conscious, you can even re-use any shallow plastic containers that have come into your home (the sort are used to store meat in grocery stores, for example). Simply give the trays a thorough wash, punch some drainage holes in the bottom, and you’re good to go!


It’s really easy to forget what seeds you’ve sown into certain trays and, even as the seeds begin to germinate, telling them apart from one another can be very difficult. With this in mind, it’s important to make sure you label your seeds after you’ve sown them.

Your labeling doesn’t have to be particularly descriptive, though. Simply make a note of the following:

  • The name and variety of the seed you sowed (“Tomato - Black Opal”, for example)
  • The date you sowed it

By making a note of the date, you’ll have a better idea of when your seedlings are ready to be transplanted. It’s also useful if you’d like to grow a succession of crops as you’ll know when you last planted the previous batch. 

Plant labels are available in a range of materials including plastic and wood, and when looked after properly they can last you for many years to come.

Planting Diary

As well as knowing what to plant and when to plant it by using a planting calendar, it’s also a good idea to keep a planting diary.

This will help you remember what it is you planted, when you planted it, and, most importantly, where you planted it!

You can also use your planting diary to make a note of your gardening successes and failures. This gives you the opportunity to look back at how things went the previous year when it comes to planning your garden again next year. 

A planting diary is also an incredibly useful tool to pass on to anybody new to gardening who might want to call upon your experience and expertise!

3. Planting Diary

The Planting Calendar: US Zones Explained

5. The Planting Calendar US Zones Explained

We’ve mentioned different planting zones above when we took a look at frost dates. But why do we have these planting zones? And what exactly do they mean?

Put simply, a planting zone determines how successfully you’ll be able to grow certain plants. Whenever you purchase a packet of seeds or a plant from a nursery, you’ll notice that it will be labeled with its own USDA Plant Hardiness Zone Number

Much like frost dates, the temperature that a plant is hardy down to will differ from state to state. You can determine what zone you live in by entering your zip code into a planting tool, and this will give you a better indication of when it’s safe to start planting as well as when you should bring your established plants under shelter for winter protection. 

Trying to grow a plant that doesn’t match with your area’s hardiness zone number will be virtually impossible, and is certainly not something that should be attempted by an inexperienced gardener. It will simply result in the plant dying and, with it, a loss of time, effort, and money. 

The colder a certain area of the country is, the lower its zone number will be. For instance, Alaska is in Zone 1, while Central & Southern Florida is at a warmer Zone 9. These zones have a massive impact on what you’re able to grow and, as such, they are an extremely important thing to factor into your planting calendar.

Below, we’ve created a list of hardy and non-hardy plants that are suitable for both colder and hotter parts of the country. This will help to give you a better understanding of what specimens you can include in your planting scheme.

Hardy Plants

Hardy plants are capable of surviving extremely cold temperatures and will come back stronger year after year. These include:

  • Peonies (Zones 2 - 9)
  • Goldenrod (Zones 2 - 8)
  • Oriental Poppies (Zones 3 - 7)
  • Common Lilac (Zones 3 - 7)
  • Hydrangeas (Zones 3 - 8)

Non-Hardy Plants

Non-hardy plants are much more tender and if left in the ground over winter may die. For this reason, they are only suitable for growing in areas that have a higher plant hardiness zone number. Examples of non-hardy plants include:

  • Bird of Paradise (Zones 9 - 11)
  • Aloe Vera (Zones 9 - 11)
  • Tropicanna Canna (Zones 8 - 11)
  • Elephant Ear (Zones 8 - 11)
  • Snake Lily (Zones 8 - 10)

Your area’s plant hardiness zone number is also a useful tool when it comes to growing fruits and vegetables. If you’re in a colder area, you’ll most likely need to start your seeds off inside a heated greenhouse or indoors on a windowsill above a radiator. If you’re in a warmer part of the country, you may be able to sow more delicate seeds directly into the ground. 

Planting & Potting Tips

6. Planting & Potting Tips

You might think that sowing a seed is as simple as burying it in the soil and waiting for it to do its thing. However, there is a little more to it than that, especially if you’re planning on growing fruits and vegetables.

From making sure you’ve planted your seeds at the right time to keeping your young seedlings well-watered, we’ve compiled a list of advice that will help your plants grow as healthily as possible. 

Time It Right

4. Time it Right

Planting a garden is all about timing. We’ve already stressed the importance of keeping a planting calendar, but it’s a good thing to reiterate here.

Regardless of whether you’re planning on sowing your seeds indoors and then moving them out into your garden later, or if you would prefer to sow them directly into the ground, you need to make sure that you’ve worked out your area’s frost dates.

It’s also important to make sure that you’re not sowing your seeds too late.

Most seeds can be sown over the course of a few months, but as you begin to approach the end of this period you start risking your chances of the seedlings not getting enough natural warmth or light.

So, for stronger plants and better crops, try and keep your window as close to the start of the sowing period as possible. 

Another reason why timing your sowings is so important is because it gives you the opportunity to grow crops successively. By sowing the same type of seeds at 2-3 week intervals, you’ll be ensuring you’ve got a constant supply of crops throughout the summer that you can enjoy for months rather than just getting one small yield. 

Growing successively also gives you a better opportunity to store your homegrown fruits and vegetables so you can continue enjoying them once the growing season has finished. 

Find Suitable Containers

A seed tray is an essential container for sowing your seeds, but you’ll also need to find suitable containers for transplanting each small seedling into once it has its true leaves.

This will give the roots room to stretch out, absorbing more nutrients from the compost as they do and, in turn, growing into strong, healthy plants. 

A lot of people make the mistake of transplanting each small seedling into a huge container. It might seem like a sensible thing to do at first, given that it will grow into a large plant.  

However, the reason you shouldn’t do this is that the larger the container is the more soil it will need. The more soil it has, the more moisture it will hang onto. 

5. Find suitable containers

Seedlings that have access to too much water can become susceptible to a condition known as ‘damping off’, which is caused by a fungal pathogen. This leads to seedlings wilting and dying. 

So, to prevent this from happening, gradually increase the container’s size before finally planting out into your garden or a final pot. 

Another extremely important thing to remember when you start transplanting your seedlings into containers is drainage. If there’s nowhere for excess water to escape, your seedlings will begin to rot at the root and die. The more drainage a container has the better, although you’ll need to make sure there aren’t so many holes that the compost is falling out!

Wash out each container in between sowing seeds and transplanting seedlings, too. This will help to prevent any disease or infections from attacking your plants and killing them off. 

Prepare The Potting Soil

6. Prepare the potting soil

You’ll need to prepare your potting soil before you can sow your seeds as well.

Many stores sell bags of special seed compost, and this is a quick and easy way to fill seed trays ready for sowing. However, one thing you should do before adding the soil to your containers is to sieve it. 

This will break up any larger clumps of earth and remove stones which, if left in place, might get in the way of your seed sending up its stem after it’s germinated.

Depending on what you’re sowing, you may also want to add some horticultural grit to your potting soil before you sow your seeds or transplant your seedlings too. 

This will aid in drainage and reduce the risk of the plants sitting in stagnant water. 


Once your containers are ready and the potting soil has been prepared, the time has finally come to sow your seeds!

When you begin doing this, it’s important to pay attention to the specific instructions listed on the packet. These will include:

  • Sowing depth
  • Space between each sowing
  • Light and water requirements

A lot of seed will allow you to ‘scatter sow’, and this basically means distributing them across the surface of the soil without having to place them specifically.

7. Planting

In this case, as your seedlings begin to emerge, you’ll need to thin them out.

Thinning out is a process whereby you evaluate your current seedlings and remove the smaller ones from the seed tray. This might seem like a harsh thing to do, especially since you’ve put so much love and care into raising them, but it gives the stronger seedlings a better chance of continuing to grow into the healthiest plants possible. 

Water, Feed, Repeat

8. Water, feed, repeat

While seeds don’t need many nutrients to germinate, they do need water!

However, to prevent the seeds from rotting or the delicate young seedlings from getting weighed down and dislodged by heavy water droplets, you’ll need to water your seeds from below.

But how do you do this? Don’t worry, it’s actually very straightforward!

Simply fill a sink or a bucket with about an inch of water and place the entire seed tray into it.

The drainage holes will allow the potting soil to absorb the water and, in turn, the seedlings’ roots will take the water up in this way. 

Seedlings also need to be fed as they continue to grow. They’ll take up a lot of nutrients from the soil itself, but to give them an extra boost, feed them with a fertilizer that’s high in Nitrogen, Potassium, and Phosphorus. 

Let There Be Light!

Your seedlings will need as much light as possible to grow.

They’ll take the light their leaves absorb and transform it into food through a process called photosynthesis which, in turn, helps them grow healthy roots systems and gives their cells a strong structure. 

Seedlings that don’t have access to enough light can become ‘leggy’.

This means that their stems become very long and thin as they try and stretch towards the light and, as such, they are much weaker. 

With this in mind, keeping your seed trays in a greenhouse or on a well-lit windowsill would be the best way to ensure they get the light they need. 

9. Let There be Light!

If you’re growing space isn’t very well-lit, you can also invest in special grow lights. These mimic the sun’s natural light and help your plants grow in low-light conditions.

Moving Out - They Grow Up So Fast!

10. Moving out - They Grow Up So Fast!

Once the final frost date has passed and you’re absolutely certain that it’s safe to move your young plants into their final growing position, it’s time to plant them outdoors where they can really begin to grow big and strong!

Before you do this, however, it’s a good idea to put your plants through a process called ‘hardening off’.

This means moving them from their sheltered position and placing them outdoors in their containers during the day, and bringing them back in at night.

This allows them to slowly acclimatize over time, rather than risking shocking them into a different temperature which could restrict their growth. 

As you did when you first sowed your seeds, you’ll need to prepare the soil ahead of transplanting your young plants. To do this, take a garden fork and loosen any compacted soil.

This will make it easier to plant into and will give the roots more freedom to stretch out and grow. It’s also worth working a little extra compost into the planting hole as well, as this will offer some extra nutrition to help your plants establish. 

One thing to be wary of when you’re transplanting your seedlings is transplant shock. This manifests by the young plant looking limp and lifeless for a while.

It doesn’t mean it’s dead, though! It has simply gone into shock and, when given a good drink of water and allowed enough time to settle, it will bounce back. If you’ve gradually been moving up container sizes, this is much less likely to happen.

Common Seedling Problems To Expect

7. Common Seedling Problems To Expect

If there is one thing that’s true about gardening, it’s that you’re constantly running into new problems. And, when you’re raising seedlings, there are a few common problems that you can expect. So, to help you worry a little less about them, we’ve listed these problems below along with a few tips on how to rectify them if they occur. 

Poor Germination Rate

One of the most common problems, and certainly most frustrating, is a poor germination rate. This means that not all of your seeds are breaking out of their protective cases and sending up the first signs of life. 

There are a few reasons why this could be happening, including:

  • Poor soil quality
  • Poor light quality
  • Not enough water
  • Too much water
  • Not enough heat
11. Poor germination rate

If you’ve noticed your seeds haven’t germinated in the time described on the packet, it doesn’t mean that all hope is lost! Evaluate the conditions you’ve placed your seed tray in and, if necessary, move it into another area that gets more light. You can also try increasing or reducing the amount of water you’re giving them and seeing if that helps. 

It’s worth noting, also, that some seeds need heat to germinate, in particular peppers and tomatoes. To help with the germination rates for these, make sure you’ve placed your seed tray in a well-lit, warm position. A windowsill above a radiator is ideal. You can even buy special heat-mats that will give a constant supply of warmth to your seedlings.

Spindly Seedlings

12. Spindly Seedlings

We have touched on this above, but the main reason for spindly seedlings is a lack of light.

This is because they are trying to reach out to get enough light to grow and, as such, the stems become thin and spindly. 

Plants are resilient, though. 

So, if you’ve noticed your seedlings are looking spindly, move them into an area with as much light as possible and they’ll soon begin to sort themselves out and grow more steadily. 

Seedling Toppling Over

As with spindly seedlings, a seedling that is toppling over simply isn’t getting enough light throughout the day and is reaching out as far as possible to try and photosynthesize. 

Again, this can be fixed by moving them into a well-lit position and, within a week or two, they will soon begin to grow in an upright position with a strong stem.

Moldy Soil Surface

A moldy soil surface is often a sign of too much water. This, mixed with light and warmth, encourages bacterial growth and the result is mold.

13. Seedlings Topple Over
14. Moldy Soil Surface

It may not seem like too much of an issue, but if left untreated the mold will steal the nutrients from the soil that your plants need and will result in weak, nutrient-deficient plants.

Luckily, sorting this problem out is very simple, and simply requires putting your seedlings through a short period of drought.

By stopping watering, you’ll be starving the mold bacteria and it will soon die off.

Once the top inch of the soil is completely dry, you can commence watering again without worrying about mold growth recurring. 

It’s tempting to try and remove the mold, but this risks damaging the delicate seedlings. If they are large enough to transplant, you can prick the seedling out of the moldy soil and plant them into their own container. If you do this, be sure to gently brush off as much soil as possible from the roots to prevent the mold from spreading into the new container. 

Purple Leaves

There are a few reasons why a seedling could have purple leaves including insect damage, poor soil quality, bad drainage, or disease. However, the most common reason for purple leaves is a phosphorus deficiency.

Plants use phosphorus to create energy which, in turn, helps them grow. Not enough phosphorus and the plant will have stunted growth and will tell you this by displaying purple leaves. 

The solution to this problem is simple. Feed your seedling with a liquid fertilizer that is high in phosphorus.

Mix it up in a container with water (preferably collected rainwater) and sink your seed tray or pots into it, allowing the soil to soak up the phosphorus-rich liquid.

15. Purple Leaves

In a week or two, you should notice that the leaves have lost their purple color and will be vibrant and green once more.

Seed Is Still Attached

16. Seed is still attached

A seed still being attached to the seedling isn’t a huge cause for concern and the leaves will eventually shake it off.

You can, of course, remove the seed case by hand but doing this risks accidentally tearing the leaf or lifting the delicate roots out of the soil.

With this in mind, it’s usually best to just leave it as it is and wait for the seedling to free itself.

Conclusion: From Seed To Plant

8. Conclusion From Seed To Plant

So, there you have it. Everything you need to know about planting next year’s garden and raising everything from a tiny seed into a healthy plant. If there is one piece of advice that you need to take on board, however, it’s the importance of planning your planting around your area’s frost dates and hardiness zone number.

Learning this information and working out what you can plant and when to plant it will give you a much better chance of creating a stunning summer display, as well as giving you the opportunity to grow some delicious produce right in your own garden. 

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