Seven Container Gardening Basics Every Gardener Should Know

Here are the things you need to know — container gardening basics — to succeed in your own garden.

One of the delights of our summer garden is our container gardening. We use them in a variety of ways and whether you have acres of gardens or a postage stamp patio, you might consider the use of containers to extend and improve the range of plants you grow.

Salvia argentea (biennial) in a container with annuals and sweet peas

What Plants Can I Grow In Containers?

To begin with, any plant you can name can be grown in a container.
 I know that some garden books will say give just the contrary advice but if I can grow plants -from bananas to cosmos and roses to zinnias in a container, I don’t see why you can’t. I used to grow my lavender collection in containers beside our front door and they lend a certain “style” and fragrance to our entrance way.

Potted tulips Image by author

What Soil To Use

Good container soil is the key to success. Use a good quality soilless mix  in the container. Don’t use a cheap brand or regular garden soil because they will compact and turn to concrete over the course of the summer. A good soilless mix is composed mostly of peat moss and perlite (perhaps with a very small amount of compost) and that’s about all.

A good soil like Pro-mix or Fafard will more than pay for themselves in superior plant performance this summer. And, they are light enough that you can still move most containers even when fully filled.

How To Feed

I also use a fish emulsion fertilizer on a weekly basis for my container plants. This stuff is the best container food in the world, producing huge, fragrant rose blossoms and jungle-like growth on our window boxes. There’s nothing else like it because it has all the major and minor nutrients a container plant needs.

Most other liquid fertilizers lack the minor and trace elements a plant requires for superior growth. Remember that soilless mixes, unlike natural mineral soils in your garden, do not have these trace elements as part of their natural composition so you have to provide them if you want your plants to grow properly.

The Essential Watering Rule

There’s a very simple rule of thumb for growing vegetables in a container or anything else for that matter: Water until water pours out the bottom.

In this way, you know all the soil, from top to bottom is thoroughly wet.

Air Temperatures To Understand

Somewhere around 83F (a bit higher for some and lower for others) plant leaves stop respiration and shut down to conserve water. They essentially stop growing. Because a plant actually gets taller, grows leaves etc at night after the day’s energy has been stored, this high day temperature will reduce the ability of the plant to grow.

In extremely high heat periods, it’s a good idea to give container plants a part shade condition — even those that grow in the sun. Simply pick up and move your containers during the heat of the day or tuck them into a part sun spot until the heat wave is over.

Not much you can do about this but you can control the next variable.

Image courtesy Pixabay

The above picture isn’t my kind of container garden but I’ve seen these (and other interesting containers on my travels)

Soil Temperatures in Containers

Soil temperatures will also stop growth through reduced nutrient uptake — the higher the soil temperature, the less food the plant absorbs.

Soil gets hotter in smaller containers — it easily approaches air temperature in small containers. Dark colored containers — such as black plastic — absorb more heat and get hotter.

Adding water to “cool down” the plant will only swamp the plant and kill it.
 The solution is to use light, reflective colored containers and to give plants some shade during the heat of the day.

Where Can I Grow Containers

The bonus of container growing plants is that you can place the container where you need it. For example, if you have a paved patio but want to grow plants up a trellis, then simply put a large container beside the trellis and plant morning glory seeds in the container. Those seeds will germinate quickly and if you train them towards the trellis (gently lay them down in the direction of the trellis when they threaten to go the other way) they’ll quickly find it and start climbing.

You could use the back of a round container for morning glory seeds and fill the front with impatiens and trailing lobelia so your container not only grows upwards but also gives you a flower show.

Multi-layer Your Planting

That’s another key to remember. Don’t just think of your containers as having just one use. We used to grow pansies under our containerized roses. The pansies would give us a great show in the early spring before the rose had leaved out and then would climb upwards into the rose when the rose shaded it. The pansy would act like a short vine and would poke its flowers out in unexpected spots. As I recall, we used a mid-blue pansy with a peach coloured rose to give a super colour combination.

You can also tuck herbs like basil into flower pots so you can harvest a few leaves whenever the need for a toasted tomato sandwich strikes (you *have* to use basil on those sandwiches if you want to really experience the joy of a tomato sandwich) I note that if a container is large enough for 8 full, large shovels full of soil, it is large enough (with daily or twice-daily watering) to grow a tomato plant.

Water Plants — Why Not?

Why not plug up the hole of a container and grow small water lilies in one. I did this last year and the lily was a great hit in the garden. I even managed to keep a few small rosy barb fish alive all summer in one clay-coloured container that was semi-shaded.

I did however discover the hard way that the high water temperatures generated in small black plastic above-ground water containers were not good for fish even if it was great for the dwarf lilies.

Image courtesy at Pixabay

Perennials and Winter Survival

One of the newest gardening trends is to grow perennials in garden containers and I confess I’ve done this for many years now. The only problem with this is with winter survival. In the case of our lavenders, they spend the winter on our porch. The porch is protected from the wind and moderated by house temperatures and the lavenders survive nicely.

Your attached garage would be equally appropriate. A garage or shed that is not protected by house heat would be too cold for good winter survival. (We don’t want perennial roots to get to 5F.)

An alternative suggested by some writers is to dig the perennials out of the pot and plant them in the garden for the winter. You can then dig them up for the container in the spring or simply leave them in the garden to grow. There is no perennial that will not survive in a large container so you are only limited by your imagination.

And that’s the essence of good container gardening. Get a big enough container (I use 16 inch clay pots) and a big enough imagination and you can extend your gardening and growing to anywhere you happen to spend some time.

I’ve answered more than these questions in my Container Gardening ebook here on Amazon. 

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Raised Bed Gardens: Advantages and Disadvantages

Raised bed gardens have their supporters, that’s for sure but they aren’t a cure…

Here’s the deal from my point of view gathered over 30 years in the nursery industry. I’m not going to sugar-coat this article because I know there are a lot of folks who really think raised beds are the greatest thing since sliced bread.

In many ways, raised beds are simply big container gardens.

I think it depends on your gardening style and garden. Here’s my experience with this style of gardening. You can either make raised bed gardens by mounding up soil or by constructing boxes (of almost any material) and then filling the boxes with soil.

These are however essentially two distinct ways of gardening and I’ll explain this below.

Image by author of his garden

Our raised vegetable bed — I built it because we only had 3-inches of soil over shale rock. The overhead supports help hold the sides upright (the weight of the soil bowed them out) and used for growing tomatoes and other vertical gardening crops.

The Advantages of Raised Bed Gardens

  • The soil warms up faster in the spring. It’s above ground level so the sun gets to work on it from the top and the sides.
  • They are closer to the gardener. Which is just another way of saying the gardener doesn’t have to bend down as far to reach the plants.
  • Superb for differently-enabled gardeners who may not be able to bend or kneel comfortably. Wide rows between the beds enable wheelchair access.
  • A good raised bed can act as a garden when you don’t have enough soil (like my garden).

Disadvantages of Raised Bed Gardens

  • Raised bed gardens use more water than soil-level beds.
  • Large (taller) beds act more like containers than garden beds so you have to modify the soils and watch your fertility if you are going to have truly wonderful gardens.
  • Can’t be walked on or if too high, over top of (you have to walk around them and this gives me more grief than any other characteristic of them — from a practical point of view in my large garden.)
  • You can’t use machinery such as rototillers to till or modify soil — it’s all hand-work. On small beds, this isn’t an issue but when I tried to make permanent large beds in the old farm vegetable garden (a very large one) then it quickly became apparent that I wasn’t going to do a lot of digging.
  • Mulch is tricky to keep on top of raised beds. It seems to migrate to the sides of the beds.
  • Expensive. I have to raise my garden beds because I have very little soil and this means the costs of 6×6 beams and the extra costs of fill and topsoil to fill up these beds.
  • In-ground raised beds (where you use a hoe or rake to create raised beds in a regular soil garden) are more work every year and this extra work isn’t worth it if you mulch heavily for weed control (heavy mulching will slow down the heating and reduce the main reason for using these raised beds.
  • Perennials and woody plants might have trouble overwintering depending on the nature of climate and the size of the raised bed (bigger beds make it easier for plants to survive).
  • You’ll still get weeds and they’ll grow in the rows as well so your weeding isn’t reduced.

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The Answer to the Question…

Should you use raised bed gardening techniques? It depends.
 I use them because I don’t have much soil where I want to garden and my raised beds help me create the necessary depth.
Are you prepared to use the increased amount of water they require? Any time you raise soil above the ground level, gravity will suck water downwards to the normal below-soil-level mark.
Do you want extra early crops of vegetables? Raised bed gardening is one answer for you and combined with other early cropping techniques can really make your vegetable garden come alive earlier in the spring.
Do you have physical challenges? Then custom building raised beds may be the answer.
Are you concerned about the high heat of summer? Then raised beds might not be the answer as the soil temperatures can get too hot for good growth of some plants. For example — high heat will make vegetables such as lettuce quite bitter.

Bottom Line:

Raised beds will be useful for some folks for the reasons above. But they’re not a panacea. They don’t provide any form of garden advantage other than a physical one and/or an early crop.

You’ll find these resources helpful for creating a great garden

Container Vegetable Gardening: Do These Five Simple Things

There are only five variables that you have to worry about to be a success at container vegetable gardening. And isn’t it nice that it’s this easy? 🙂

#1 Use The Biggest Pot size

This is one place where bigger is better.
A plant such as a tomato, that can easily reach 6 to 8 feet tall and a single growing season and produce 100 pounds of fruit, requires a significant root space and water reservoir in the soil.

The minimum amount of soil that you can realistically use is 6 to 8 shovels full of soil. (plan on more) This minimum will require a daily watering most of the season, and twice a day watering in the heat of the season.

This means bigger is better (at least in this one example)

Stressing a plant such as a tomato with a slight lack of water will create disease conditions such as blossom–end-rot.

Small pots lead to watering problems which lead to this major fruiting problem. In this case, it’s a physiological disease as a result of a lack of calcium being moved to the fruit and some people think that adding calcium to the soil is the solution. The vast majority of soils do not require extra calcium, but the plant does require water to move the calcium up to the fruit.

So a lack of water will create problems in the harvest. You can read more about these black spots on the bottoms of your tomatoes here

Another variable with pot size is soil temperature. Smaller pots have higher soil temperatures then larger containers and the swing between high and low temperatures is also greater

This swing in soil temperature will also reduce harvests. When the soil temperatures get too high, plant growth will slow down or stop.
Note that stressed vegetables such as lettuce will taste bitter.

#2 Get the Container Soil Right

Container gardening requires a different kind of soil then normally found in garden soil. The bottom line is you want a soilless mix with a peat moss base rather than any kind of garden or potting soil.

The mechanical forces on the soil in a container are much greater than the mechanical forces in regular garden soil

For example, when you water a container you are applying significant depths of water and pounding the soil in such a way that it will not be replicated in normal garden soil unless there was a flood

Think about it for a minute, in a container you apply 1 inch of water in the space of 1 to 2 min

Imagine what would happen if 1 inch of water came down as rain in only a minute or two. (You *really* don’t want to be out there in that storm!) 🙂
For this reason, we use  peat-based soils such as Pro–mix that are designed to withstand this kind of watering pressure.

Do not add regular garden soil to any container. And read the label on the bag – if it says “garden soil” or “topsoil” do not use it in a container.

#3 Watering Properly – A Simple System

The rules of thumb for watering any container apply equally to vegetable container gardening.

Use your finger.

  • Put it on the soil and if it comes away dry, water heavily and thoroughly so that water pours out the bottom of the pot.
  • If your finger comes away damp, do not water at this time.
  • If you do this in the morning, check again 8-10 hours later in the shoulder seasons (spring and fall) and 4-6 hours later during the height of the summer.

Early in the season, you may find that watering is not a daily chore but later in the heat of the season when the vegetables are growing strongly, you may indeed find that twice–at–day watering is necessary.

This is why really large pots have an advantage over the smaller ones – more even availability of water.

#4 Feeding For Growth and Flowers

Doug’s first rule of gardening states, “You only have to feed your plants if you want leaves, flowers, or fruit.”

This is pretty simple gardening, you feed if you want to see good growth and good harvests.

This is not an option.

I’ve had a lot of gardeners tell me they don’t feed because their soil is “good”. (Doug goes speechless when this happens)

In a container, I try to feed at least once a week during the height of the harvest season to keep the plant growing and producing well.

A weekly feeding earlier in the season is fine. In our greenhouses when we were growing commercial tomatoes, I used to feed every time I watered (daily) with a weak solution of fertilizer so the plants were never nutrition–starved.

I normally recommend fish-emulsion because I’ve had great results with it. But any organic liquid-based fertilizer is fine.

#5 What plants can I grow?

I really do not understand the confusion about growing plants in a container. If you follow the four major rules above with regard to pot size soil, watering and feeding there’s absolutely no plant that will not grow successfully in a container.

  • It’s far easier to ask, “What plants can’t you grow?”
  • If you can grow it, you can grow it in a container.

Mind you, there’s always somebody trying to sell you some new gizmo or technique to “help” you.

But no gizmo can possibly substitute for the 4 gardening techniques above. And here are my posts about specific plants

Relax

This isn’t rocket science, it’s simple gardening. If you get your watering done properly, and feed your plants every week, then you’ll be surprised at just how easy this kind of container vegetable gardening is.

Click here to get everything you need to know about container gardening

How To Make Your Own Grow Bags of Compost

Yes, you can use old pantyhose or garbage bags to make your own grow bags. Here’s how.

OK, so it’s silly season in the greenhouse research area.

Use Old Pantyhose

Some researchers have taken old nylons (looks to be about that size anyway) filled them with compost to make their own grow bags and started growing in them.

Their results indicate that this indeed might be a good way to grow plants. They state that this might work in areas where there is no soil.

Ah yes. We’ve been doing this for years folks.

Use Green Garbage Bags For Inexpensive Grow Bags

I used to grow tomato plants in green garbage bags back in the early ’80s because I couldn’t afford the fancy grow-bags.

Lay the bag on the ground, fill it with a minimum of 12 shovels of soilless mix and away we’d go. After the crop was done, pick up the bag and old stems (carefully because it would be wet) and dump it into a compost pile for recycling onto the garden. Re-use the bags if they were OK (hey, they cost me a dime each!) :-). This was inexpensive gardening using what we had.

I’ve even taken bags of soilless mix (the 30-litre size) cut a hole in them and grow on the greenhouse floor rather than ground. This was rather more expensive than the old garbage bags but I wanted to see if it was workable. (it was).

Poke holes in the bottom of the plastic bag to allow the water to drain.

Real soil or potting soil in bags does compact so if you want to try this, stick to the peat-based soilless mixes.

If you’re looking for container gardening tips, click here

Put the garbage bag in a funky container

Image by RitaE from Pixabay

Can you use straight compost as a growing media?

Yes, you can *if* your compost is fully composted.

If it is not (or you’re in doubt) then only use it at 10% of the total volume of the soil (in other words, 1 shovel of compost for every 9 shovels of a peat-based soilless mix).

Fully composted material is fine — partially composted material may contain too many salts and burn tender seedlings. Here are the posts on how to make compost

As always, if you’re not sure try growing some tomato seedlings as they’re the most sensitive plants in the home garden. If they grow well, you’re fine.

But yes, a researcher has just figured this out. Good to know. And if you do have lots of extra old nylons around, you might give them a try. The only issue is to ensure you have adequate soil, support, and water for your intended crop.


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You Can Succeed Growing Herbs in Containers

You can succeed growing your herbs in containers if you take a few things into consideration.

Do note the feeding regimes – this is different than growing herbs in the ground.

Use a Big Container

Use the largest containers you can. You’ll find the growth of culinary herbs is much better if given the root space and not squeezed tightly together.

I tend to use a minimum of a 16-inch pot for my container herb gardens.

Soilless Mix from Top To Bottom

Many gardeners use soil from their gardens or regular potting soil (the kind you use for houseplants that contains real soil).

This is a mistake for container gardens.

Use a soilless mix such as Promix. You do NOT want any real soil in the container because it will turn to concrete as the growing season progresses. (The weight of all the water you’re going to put onto the pot all at once every time you water will smush the soil particles together. So if there’s any clay at all, it will compact terribly.)

Check the label – even some of the most popular and heaviest advertised potting soils contain real soil and you do want to avoid this. (What happens if you do use real soil? The soil will compact too soon and your harvests will go down.)

Use the same soil from top to bottom of the pot and don’t put shards or anything on the bottom of the pot to “improve” drainage. Adding larger material actually slows down drainage.

If you’re growing annual herbs such as basil, then adding 10% compost to the soil is a good idea to keep the plant growing strongly.

Otherwise, use fish emulsion at recommended rates every two weeks.

If you’re growing perennial herbs, then a mix of compost is acceptable or a monthly feeding of fish emulsion will keep the herbs growing but not turn them too soft.
Grow as many herbs as you can in the same container. My rosemary container (I overwinter it indoors) contains two varieties. It used to have three but I killed one accidentally. I have an upright variety growing up and a trailing variety growing over the edge.

Feeding and Harvesting

I know you want to know – if you’re growing a combination – I’d feed every two weeks.
I use fish emulsion.

The simple deal is that while herbs growing in garden soil don’t require feeding, there’s an important difference to understand.
In regular garden soil, there are a great many micronutrients plants require but in soilless container soil, there are almost none. You have to provide them if you want to see growth.
In regular garden soil, there are essential nutrients at low levels (nitrogen etc) but again, these don’t exist in soilless mix. You have to provide them.
You’ll simply get a better crop if you feed your container herbs.

Harvest regularly (even if you don’t need the herb) to keep the plant producing new, tender shoots.

Your Plant Choices

Grow what you’ll use most of.  For example, most folks I know will use and really enjoy fresh basil with tomatoes. And the rules for growing basil in the garden (pruning etc) are the same for in the house.

  • Start simple.
  • Start with annuals because they’re the easiest and don’t require a dormancy period.
  • Note that perennial herbs really don’t come into their own until the second year after planting.
  • Start with what you use.

Sunlight Levels

  • Put the pot in the full sun. Herbs don’t grow well in shady conditions.
  • In shade, you’ll get some growth (spindly and weak) but the taste/flavor is watered down by the spindly weak growth.

Container Herb Gardening Locations

  • Put the herb container where you’ll be able to harvest it easily and regularly. In the full sun.
  • If you have a regular garden, use the container grown herbs for quick pick-me-ups for taste in drinks or salads. A little basil, a little mint, small chives, a touch of oregano – grow what you’d use in quick cooking. Put the main crop of normal herbs and those you only use once in a while out in the ground-garden.
  • In a patio gardening herb garden, mix and match your herbs – growing the taller herbs in the center of the pot and the shorter ones to the edges. Plant any trailers or ground cover types on the edges and let them find their own airspace.

Overwintering

  • Plan on taking the container indoors in the fall and harvesting it until the plants run out of energy and sunshine (becoming spindly or dying). Full sunlight and cool temperatures (low 60’s to mid-50’s F) will prolong this fading away.
  • When annual herbs start to fade, toss them into the compost.
  • I don’t try to keep perennial plants growing but when I bring them indoors, they go immediately into the cold cellar for the winter.

Tropical perennial herbs (lemongrass etc) need full sunlight and warm temperatures to continue growing so you either provide these or the plant will fade and die.

Will Perennial Herbs Live Over The Winter If I Dig Them Up From The Garden

As a rule of thumb, they’ll live for a while but stop growing around December and by the end of January, they’ll look really poor.

And then when you put them back outside again, they’ll languish for the summer.  You see, perennials want and need to go dormant and when you bring them indoors, they don’t get the rest they need.

What About Parsley? I’ve Read You Can Bring That Indoors

True. It’s a biennial so if you bring it indoors, it will continue growing and then you can toss it out in the spring and start with a new plant.

Feeding The Plants

In the garden, we tend not to feed herbs too much.

But in a container, those rules don’t hold true. For best results, you do want to feed an organic liquid fertilizer on a weekly basis to keep those annual herb leaves coming along.

Pruning and Harvesting

When you harvest leaves from the top of the plant, it stimulates growth from below the cut.

But in the winter, there’s not much light to stimulate new growth. It will take a while to get those side shoots performing but the rule of thumb still holds true. Pinch and prune from the top to get the plant to bush out and then take uniformly from the mature shoots.

How Long Will The Herb Last

Well, that depends on how hard and how often you harvest the leaves. There’s no hard and fast rule here – it you give a plant enough light to keep it growing (hard to do without grow lights in the reduced light of winter) then it will produce as much over the winter as it does in the summer. My ebook on growing herbs is here.

But as the winter light levels go down, production will go down.  That’s the Internet’s way of saying it all depends on how much light and heat you can give the plant and there’s no way that one size fits all.

Heat? Yes, don’t forget that the temperature on a windowsill in the winter is going to be colder than the room temperature and that annual herbs want all the heat and light you can give them.

Doug’s Bottom Line

It really isn’t rocket science and herbs are really no different than other plants.
The most important advice I can give you is to simply do it. Enjoy the experience and do brush your hand against the herbs now and then to get those delicious.

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