Spring Gardening

Check the Temperature Before You Plant!!

Erica3 Comments
Several trays of pepper seedlings in quart-size pots sit on a deck getting used to outdoor temperatures.
Pepper plants hardening off

A short post today, in which I make my annual plea to hold off on planting summer vegetables until it’s warm enough. Please – your garden will thank you later!

We have some guidelines on the HGIC website about when to plant vegetables and how to harden them off (get them used to outdoor conditions). Remember, though, that planting isn’t about dates; it’s about temperature. It is not a hard-and-fast rule that your tomatoes should be in the ground by Mother’s Day. What if it’s 40 degrees on Mother’s Day? Bad for outdoor brunch, but also bad for young tomato seedlings.

The round temperature dial of a compost thermometer registering about 55 degrees Fahrenheit.
A compost thermometer is useful for checking soil temps

In general, vegetables that prefer summer’s heat also don’t like spring’s cold. Tomatoes, peppers, squash, cucumbers, and all their friends want soil temperatures over 60F and air temperatures over 50F (including at night). Try to wait to put them in the ground until the forecast shows at least a week of these conditions, with no cold snaps or heat blasts. Of course, spring is full of crazy ups-and-downs (especially this spring) but if you can give the plants a good start, they will tolerate temperature swings better. If a frost is predicted, or really anything below about 45, throw some kind of covering over the plants: heavy-duty row cover if you have it, but a sheet or light blanket will do.

Get to know your garden’s microclimate – if it’s protected from strong winds, plants will tolerate cold better; if it gets a bit of afternoon shade, they will get through high heat with less damage.

You can purchase all kinds of devices to give your plants extra protection, but after trying them all I found I preferred just having some patience. If you do use them, make sure they’re easy to put up and take down – struggling with a complicated shelter in wind and rain is no fun, nor is removing the whole thing again when it’s 85 the day after dropping to 39.

I know, all my plants are huge too, and really want to go outside. But I’m going to wait until it’s time.

By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.

Spring Crops in Containers

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Lettuce and arugula seedlings growing in a terracotta-colored rectangular planter
Salad greens like lettuce and arugula are easy to grow in various sized containters Photo: Erica Smith

Maybe your first thought on starting a container vegetable garden was “I can grow tomatoes!” Which is great—but tomatoes are a summer crop and it’s not time to put them outside yet. You can start your garden even earlier, though, with spring plantings.

Here are a few of the spring crops you can grow in containers:

The only spring crops I would hesitate to grow in containers are large brassicas like cabbage, broccoli, and cauliflower, and even those could be planted in containers—it’s just that you would only plant one per pot, which might not be worth the effort, unless you have space for a lot of pots, no in-ground garden, and a real love of fresh-grown cabbage.

I’m also not a huge fan of potatoes in containers, because they don’t usually produce very much and it doesn’t seem worth the space and expense when potatoes are so cheap to buy. Nevertheless, I’m going to give it another try this year, just so I can report back here!

Here are some tips on planting spring crops in containers:

  • In some cases it may be more practical to start with transplants rather than planting from seed. This allows you to get the spacing just right and eliminates tedious thinning of extra seedlings. It’s also much faster. But seeding also works fine.
  • Consider the shape of the container when choosing a crop (or vice versa). Crops you want to harvest a lot of, like lettuce or radishes, will work better in a wider container. They also have shallow root systems, so the container doesn’t have to be very deep. Whereas if you’re going to grow carrots, make sure you have a container several inches deeper than the expected carrot length.
  • The usual container growing guidelines apply: use lightweight potting mix rather than real soil from the ground; water frequently; apply fertilizer as needed.

Here are some photos of spring crops growing in containers:

Pea plants in a black fabric grow bag with sticks for them to grow up
Chive plants in a rectangular container
Lettuce, arugula and chard in a raised planter with legs
Seedlings of lettuce and brassicas in a square white raised planter

Photo collage from left (click image to enlarge): peas in a fabric grow bag (a great inexpensive option for lots of crops); chives in a rectangular planter (herbs are wonderful container crops); lettuce, arugula and chard in a raised trough planter on my deck; various spring greens in a keyhole garden, which has an area in the middle meant for creating compost to feed the plants. Except for the trough planter, all of these are from the Special Projects area at the Derwood Demo Garden.

This does bring up a question: what counts as a container? The raised keyhole garden and raised trough planter in the photos are much larger than the typical pot or planter, and may be closer to a raised bed. There’s certainly a fuzzy line between the two types of gardening.

To my mind, a container is an object that holds growing medium more likely to be potting soil than real mineral soil from the ground, and that could sit on a deck, patio, or driveway rather than being situated in a typical vegetable garden layout. I definitely consider my trough planter to be a container, if a very large one. The keyhole garden is an edge case, maybe more of a raised bed the way we use it at the Derwood Demo Garden in Montgomery County, Maryland. But it could be a patio planter, so I’m happy to regard it as a container as well.

In any case, it’s time to get those spring crops growing if you haven’t already! Happy spring!

By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.

Related information:

Growing Vegetables in Containers and Salad Tables

Q: We have some welcome respites of very mild to warm weather in the forecast. When can I put some of the plants I overwintered indoors back outside? I’m sure they miss the better light.

Emily Clark WatersonLeave a comment
A vaiegated spider plant and some succulents in containers on a balcony.
Some houseplants are tougher than others but most are not ready for full sun or the cold nights of early April. Photo: Anna/Adobe Stock

A: It’s easy to get caught-up in the moment during those lovely spring-preview days and want to liberate your houseplants to bask in the great outdoors. I know I’m antsy to get mine back outside. Try to wait until at least our last frost, though, which for central Maryland averages about Mother’s Day. Some tropical plant species are more sensitive to cold than others, so you may be able to start the acclimation process for the tolerant ones earlier, if you pay attention to overnight temps and bring them back in when needed. In comparison, some may sulk if they’re exposed to temperatures below 60°F. If unsure, err on the side of caution; exposure to no chillier than 55-60°F is a good assumption.

All plants, no matter how sun-loving they are, need time to adjust to the brighter light moving from indoors to outdoors, so they don’t sunburn. Shade outdoors is usually much brighter than direct light indoors, even though to our eyes it doesn’t look that different. Put anything you bring out into shade first, gradually introducing them to greater amounts of direct light (based on their needs) over a few weeks.

Even plants that need bright light inside don’t necessarily want unobstructed full sun outside, even once acclimated. Potted succulents and air plants, for instance, tend to fare well if shielded from the strongest afternoon summer sun by some dappled shade from either trees or shade cloth, or by a passing shadow from a building or fence.

Various potted plants and herbs growing on a balcony with a railing and a large tree in the background
A cozy balcony garden filled with various potted plants and herbs in mid summer. Photo: Emily Clark Waterson, UMD Extension

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

Breaking the Rules For Hardening Off

Maryland Grows2 Comments

You won’t find a lot of experienced gardeners—at least those who are honest with themselves—talking about “rules” in gardening. That’s because, strictly speaking, there are very few of them. There are certainly guidelines, which are created through a combination of experimentation, synthesis of results, lots of mistakes and corrections, and effective communication of principles. There’s also a lot of bad advice out there, which you can weed out in simple ways (try using “Extension” as part of your web searches) or by disregarding those helpful nuggets that use only anecdote or tradition as rationales. (“This happened to me once, so it must always be true!” “My grandmother always said…”) Personally, I think you can also ignore pundits who declare rules without exceptions. There are always exceptions.

Or maybe I’m saying that because I just broke a rule. It’s May, so time for hardening off seedlings. The guideline for hardening off is to introduce your young plants to the outdoors gradually. Carry your tray full of pots outside and put them in a sheltered spot (out of the wind and sun). Give them a few hours of outdoor conditions and then bring them inside again. Next day, lengthen the time outdoors. Over a week, expose the plants to more sun and some light breezes. Leave them outside overnight on the last few nights before you plant them in the garden. This way, they don’t get shocked by a sudden change in exposure, and they will settle into their new life more readily. Failure to make this gradual transition could result in a serious growth setback, or even in death. (Of the plant. You’ll be fine, I hope.)

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Beyond Broccoli Part Two: What’s Up with Brassicas?

Maryland Grows1 Comment

Welcome back to Beyond Broccoli! Last month I posted about how the genus Brassica is classified and grouped, and where the plants come from in the world. Now let’s talk about what characteristics the brassicas have in common. Here’s some of what they share as a group:

  • An origin in temperate regions. These species originated in Europe and Asia, and most of them prefer to grow in cooler weather.
  • Thousands of years of cultivation and breeding. They’ve been part of humanity’s diet for a long time, and have great cultural significance in many regions.
  • Some physical similarities. I mentioned the cross-shaped (cruciferous) flower in the last post. Brassica seed leaves (cotyledons) have a characteristic heart shape, and seeds are generally small and round. We’ll explore leaf pigments and other commonalities in later posts.
Seed leaves of mustard
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