What to Do in the Garden in December

March 1, 2020 JMJ

Cuban oregano isn’t frost-resistant, so either dig it up and keep it inside for the winter or be ready to lose it. Knowing what is vulnerable is key to navigating colder temps.

December brings unpredictable weather. Ideally, we experience some rain and mild frosty nights before severe freezes, allowing our crops to gradually prepare for the colder temperatures to come.

Looking back at my garden notes from previous Decembers:

2022 Some nights in the upper 30º, a LOT of rain, only one light freeze. This is ideal.

2021 We’ve been lucky with weather so far this fall *loudly knocks on wood*. November was glorious! I’m still harvesting baskets of tomatoes, peppers, and eggplants while at the same time temps have been mild enough for radishes, lettuces, and brassicas to thrive.December 2021 ended up being the warmest in Austin’s history. It led to a lot of cool-season crops not making it through the later freezes as they did not have any hardening off. Or you had to constantly make sure you protected crops for these one-off cold nights and it was more difficult than it should have been to say, keep your ranunculus alive. That is usually not an issue.

2020 After a November that regularly served 80º+ temps:

Well it’s happened. It’s finally fall in central Texas! Even as I write these words, the sun is just starting to melt the frost covering the garden and it is transformed! Zinnias so lovely just yesterday, now look like something from Miss Havisham’s ancient table setting. The still-thriving eggplants and peppers that were producing with renewed gusto are now suddenly shriveled and twisted. It’s sudden. It’s beautiful. It’s necessary. They say, “To every time there is a season,” and finally, that applies to us.

November was hot. Too hot. Your newly planted fall crops may have struggled because of the heat. Your brassicas may have been attacked by cabbage or army worms. Your radishes may have bolted. None of that was your fault. It is much easier to garden when plants are provided their ideal conditions. We can follow the planting calendar and hope for the best, but cool season crops want it to be cool. You’ll find that if you can keep the squirrels away, gardening in December can be the easiest, most carefree experience yet. You don’t have to water that frequently. There’s not as much to do so you can plan and relax a bit. The mosquitoes take a break. The heat subsides. The toil of gardening takes a holiday.After that hot November, we went on to have a great growing season until February, when the legendary Texas Freeze came for us all in early 2021.☹︎

December Garden Tasks

Review & Reflect

You’ve done a great job, and I am proud of you! I see my garden as a mirror of my year, reflecting both highs and lows without judgment. After my sweet spaniel, Stella, passed away in March 2021, I neglected the garden for a while. In 2023, I started a new full-time job, so I couldn't care for the garden as I did during the pandemic. That's just how it goes. Your garden is unique; no other garden is like it. What have you learned about yourself through gardening this year? When your summer plants die in the frost and your perennials rest, take a moment to look at the landscape you've created and the ecosystem you've nurtured. Be proud of yourself. This is also a good time to think about adding permanent features to your garden.

Plant roses, trees, and cold-hardy shrubs

Bare-root roses are best planted in December and January. Consider treating yourself to a special rose. If you have already have roses, more on that later. You can plant trees and hardy shrubs this month. Next month and February is best for planting fruiting trees and vines, so start preparing a spot with compost and leaf mulch. Once frost arrives and the garden loses its greenery, you may notice places where adding evergreens could provide structure and interest year-round or areas where some cool season annuals could provide a fresh pop of color to a newly barren landscape.

Pansies and violas are easy to grow, cold-tolerant, for the most part pest-free, and the flowers are edible! Joy to the Max.

Fill in the empty spaces in your vegetable beds with salad seeds and edible flowers

You can brighten up the newly created empty areas with annual flowers. A lot of the flowers you plant this time of year are edible! Combine those with a lettuce bed and you’ll be amazing yourself with the beautiful salads you prepare all winter long. This is something you can totally do now by the way. If you’ve not been able to get your garden going, or you did but then the bastard squirrels thrashed it, do this one thing. Prepare one bed that you can protect. Plant some lettuce seeds & winter green transplants and some pansies or violas from your local garden center and get that bed going. Sow spinach seeds and radishes and in a few weeks, you’ll have baby greens to devour daily as you natural thin your seedlings.

Sow new seeds every three weeks to keep baby leaf spinach and other greens coming. My Salad Days Seed Collection is a great place to start.

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Fertilize only your vegetables

You don’t need to fertilize anything other than cool-season crops this month. You want to encourage everything else to go dormant to prepare for winter rather than expending energy on growth that will be vulnerable to freezes. I like to spray my veggies with alternating feeding & pest management treatments. I recommend getting one of these bad boys to help because spray bottles always fail or tire my hand. Each weekend I alternate using it to spray seaweed or fish emulsion for nutrition and BT (Bacillus Thuringiensis) for defense against caterpillars. Be careful with the latter treatment to keep it from blowing onto your fennel, parsley, or rue which swallowtails will munch on come spring. BT only works against caterpillars but it works on all caterpillars, including monarchs and other beloved species, not just the cabbage loopers munching your brussel sprouts.

Cut back on watering

It’s not nearly as hot or dry as it has been so you can reduce your water use tremendously. Your big brassicas want deep waterings 1-2 times a week. Carrots, radishes, and lettuce need to be watered enough that if you stick your finger down 2” in the soil, it’s still moist. You never want those three crops to dry out completely or it will affect their flavor but you definitely don’t need to water every day.

If a freeze is in the forecast, that is when you want to water everything you care about protecting deeply. Think of the water like a blanket you are creating over their roots.

Snapdragons in the foreground, newly dead zinnias in the background.

Leaf Mulch & Lawn Care

Use fallen leaves to create paths in your garden or fill in areas where you are trying to kill grass by layering cardboard & paper, watering in, and then covering with leaves. By springtime, you can just add soil directly on top of these areas and have new garden beds with no effort on your part. If you don’t have leaf mulch on your lawn, grab it from a neighbor’s curb when they fill up bags for collection. You can mow over leaves to shred them into your own lawn. Leaf mulch will help fertilize your lawn but you don’t want it to be so thick as to block sunlight entirely or it will disrupt photosynthesis and kill the grass.

Inspect and protect your fruit trees and roses

Remove any old “mummies”- dried fruit or blossoms- from your fruit trees, bushes, and vines. Pick up any fallen fruit and do not compost. This will help keep any disease that may be present contained. Treat your dormant fruit trees with sulfur or a biological fungicide once they drop their leaves. Prune any deciduous trees like crepe myrtles or vitex that need it once they are dormant. You can see their shape now that the leaves have dropped. You can do this until they start leafing out in the spring.