Episode 10 – Winter Containers, Moist vs Well-Drained Soil, and More!

Ground Breaking Banter

In our first segment, Stacey and Rick tackle the question of whether  it’s possible to overwinter shrubs in containers. The answer is yes! If you can, sink the pots and/or plants in the ground to overwinter them; another possibility is to move them to an unheated garage or similar space, provided they offer good natural light. Your main goal should be to protect the roots against the freeze-thaw cycle. 

Here are a couple of helpful guidelines:

  1. Use large containers, and make sure they are made of a weatherproof material that can withstand winter weather. This means typically avoiding ceramics and terra cotta.
  2. Choose a shrub or perennial that’s ideally be two zones hardy than the zone you live in. While this is more of a guideline than a rule, it helps ensure the plant can withstand any excessive cold it may experience due to a lack of insulation.
  3. Perennials and shrubs are best overwintered outdoors, but an unheated garage, buried in the ground, or transplanted are also viable options.
  4. Check the plant every 10-14 days for water. If the soil is dry, water only enough to wet the soil surface. Don’t attempt to water until it flows out the bottom, as you would in summer. 
  5. Do not fertilize through the winter. When active growth begins in the spring, start fertilizing the plant.
  6. Huddle for warmth. If you have multiple containers, group them together and place them in a protective corner. Also, they’ll be more protected from cold if you put them on the ground rather than up on a deck. And avoid locations with prevailing winds. In some climates, it may also be beneficial to cover them with mulch to provide even more cold protection.

The Word of the Day is: geotropism, sometimes called gravitropism, is the response of plants to gravity. Stems that grow upwards, away from gravity,are said to be exhibiting negative geotropism. Roots grow downwards, towards gravity, and are said to be positively geotropic.  

Why? All this talk about winter and whether shrubs can survive winter in a container got me thinking about hardiness, the measure of how much cold a plant can withstand, so I thought we’d talk about one of our hardiest shrubs – Celtic Pride microbiota, also known as Siberian cypress. With the word “Siberian” there in its common name, that already gives you a big hint that it’s from a notoriously cold climate and will be able to tolerate some pretty harsh winter weather.

Celtic Pride microbiota is a low growing conifer with really beautiful, almost fern-like evergreen foliage. It’s just 1-3’ tall, but reaches 4-6’ wide. If you’re having trouble imaging what it might look like, try to picture a nice-looking mophead on the ground, but it’s a beautiful silvery-green color of ferny foliage. I’ve always found that it’s a plant that, when people see it, they instantly love it, but it kind of flies under the radar at the garden center. It’s a shame because it’s really beautiful and useful, and makes a nice ground cover, edging plant, looks great at the corner of a bed or lining a walkway, and it’s quite durable too.

The story behind Celtic Pride: conventional microbiota are plagued by one issue – tip dieback. This isn’t the normal leaf loss we’ve covered a couple of shows ago – it’s kind of like a disease that would just cause the tips of the branches to turn brown out of season. Celtic Pride was selected by a large grower on the East Coast, where they noticed it did not get the dieback like its neighbors did. It also has the advantage of turning a more vgivid than conventional varieties, which turn kind of a muddy russet. That color is kind of polarizing. I like it, actually,but even if you don’t, it’s usually buried under snow anyway because it is so low growing.

How to grow: Celtic Pride microbiota is hardy to USDA zone 2 but, like many very hardy plants, it’s not terribly heat tolerant – only through USDA zone 7. 

Ready to add Celtic Pride Siberian cypress to your landscape or garden? Ask for this Proven Winners ColorChoice Shrub at your favorite local garden center.

Gardening Mail Bag

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Rick kicks us off with a question of his own: What is meant by “moist, well-drained soil?” Stacey admits it’s a phrase that’s used a lot on plant tags and websites, but not usually explained. Here’s how she breaks it down: a given soil is ideally made up of 50% soil particles and 50% air spaces between the particles. When it rains, or you water, those air spaces fill up with water and wet the soil particles. In a well-drained soil, the water quickly drains out of the air spaces, restoring oxygen to the plant roots, and leaving the soil itself moist. In a poorly drained soil, the water in the spaces sticks around for longer, sometimes very long, depriving the roots of oxygen and literally suffocating them. You can test whether your soil is well-drained by digging a hole (as if you were going to plant a good-sized shrub – you can use a two or three gallon container for reference), filling it to the top with water, and then checking on it in half an hour. If, after thirty minutes, there’s no standing water in the hole, you’ve got “well-drained soil.”

Fred is looking for some advice on how to prune Fire & Ice hydrangeas:

Thanks, Fred, for our first hydrangea pruning question of the season! Fire & Ice is a panicle hydrangea, and while it’s not a Proven Winners ColorChoice Shrub, we are always able to offer our advice on growing these beautiful, hardy hydrangeas so they look their best. 

Panicle hydrangeas bloom on new wood, so they can be pruned in spring. While pruning isn’t imperative, cutting the plant back by about one-third its total height and removing any thin side branches will give you thicker, more vigorous growth with better flowers. You can get an easy-to-follow look at the process in this video. Whether you choose to prune in fall or spring is up to you. We prefer spring pruning, because it’s nicer to look at the flower skeletons all winter than a bunch of cut-off branches. Plus, spring pruning gives you the advantage of seeing where the new growth is coming from, so it’s easier to decide where to cut. If you do opt for fall pruning, be sure the plant is completely dormant – no green growth left at all – before doing so. 

Krista has a question about a Southern plant, crape myrtle:
My sister just had four crape myrtles cut down in her yard due to having bark scale. She would like to plant some kind of new trees in the spring, but is it necessary to treat the soil first since the bark scale was so bad?

There’s no need to worry about planting another crape myrtle in that same spot. Scale is an insect that physically attaches to a plant and spends its whole life there, so once the tree is gone, so are the scale. That’s not to say that scale can’t come back – the juvenile scale insects can become airborne – but this would be coming from a different tree, not the spot itself, since the scales will not live in soil. 

This issue is not unique to crape myrtle – there are lots of other trees and shrubs that get scale, especially in the South. Click here to learn more about this fascinating insect!

Branching News

Here are the links to the stories we covered in branching news this week:

including adding more plants to our diet, goats out of control, a surprising squirrel find for a Virginia couple and don’t hit golf balls into the Grand Canyon and post it in social media. It’s sure to get you in trouble!

A plant-based diet – or even a partly plant-based diet – has plenty of benefits. So what keeps people from doing it? This survey dives in to the objections American have

A band of mischevious Kashmir goats are wreaking havoc in a Welsh town – learn about the task force being assembled to deal with them

A couple in Virginia were stunned to find a squirrel swimming in their toilet. How did it get there? What did they do? Find out in the article!

And in the “please never do this” department, a woman has been federally charged after posting a video of her hitting golf balls into the Grand Canyon on social media. 

A hydrangea in a low decorative container covered in pink and purple mophead flowers.

Episode 96 – Garden Regrets

Regrets? We’ve had a few, and maybe you have too, which is why we’re dedicating this episode to the things we wish we had – and hadn’t – done in the garden. Featured shrub: Let’s Dance Arriba reblooming hydrangea.

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