Written by Melissa Strauss Horticulture review by Sarah Jay Last updated: March 28, 2025 | 3 min read

I’m not sure how it happened, but broccoli is always a hit on my dinner table. Even my four-year-old is happy to hear that this tasty and healthy vegetable is on the menu. Growing it in my own zone 9 garden isn’t always as easy as getting these kiddos to eat it, though. 

Broccoli is a cool-weather cruciferous vegetable. It prefers the mild temperatures of spring and fall, so in places where the spring heats up quickly, it can be a challenge to grow. It needs a lot of sun, but the afternoon exposure can get too intense early in the season. Fortunately, for cool-climate gardeners, there are fewer hurdles to overcome. 

No matter where you grow it, there are some important factors to growing a healthy, booming crop. Let’s take a look at some potential mistakes we can make and how to grow the perfect heads in your garden. 

Mistake 1: Starting Too Late

In warm zones, plant this in fall for winter harvests; it sweetens after a light frost.

Because broccoli prefers to grow in cooler temperatures, it’s an easy mistake to miss the ideal planting window. This is especially true for warm-climate gardeners. If you don’t start those seeds on time, you can run into a couple of issues. 

Depending on your zone, you can grow this crop in spring or fall. In warmer climates, you may find that fall sowing for a winter harvest is more conducive to the overall success of your crop. It’s a frost-resistant vegetable that actually gets tastier after a frost or two. It’s like many leafy greens in this regard. 

Because broccoli needs cool temperatures to germinate, starting it in the late summer and early fall can be challenging. This mistake is much easier to avoid in cooler climates, as the growing season for broccoli is longer here. 

You can directly sow seeds in the garden as soon as the ground is workable. However, the seeds are small and tend to do better if you start them indoors. In warm climates, you can start them about six weeks before transplanting. Since they are frost tolerant, this may be as early as December.

In cool climates, plan to move them outdoors as soon as the ground is workable or about four to six weeks ahead of your last frost date. Start them roughly six weeks ahead of transplanting. Place them in a cool location and forgo the seed heating mat for these. They germinate well at about 60°F (16°C).

Mistake 2: Crowding Your Plants

Give seedlings enough space, or they’ll grow weak, spindly, and develop shallow roots competing for nutrients.

Give your seedlings a space of their own when you start them. If you sow too many seeds in one cell, your baby plants can grow leggy and tall, which is something you don’t want. These will be weak and spindly and won’t have great root development because they share that small space. 

Mistake 3: Waiting Too Long to Transplant

These plants need cool weather for strong growth; avoid planting in consistently warm seventy-degree temperatures.

Another common mistake is waiting too long to get your transplants into the ground. This creates two issues. The first is the strength of your plants. If you leave them in a small cell for too long, they won’t have space to grow strong roots. They will instead grow tall and spindly, which makes for weaker broccoli. 

The second issue is their need for cool weather to do the bulk of their growth. It’s better to expose them to frost than to wait until you’re consistently experiencing temperatures in the 70s (~21°C). If you don’t give your young plants ample cool weather to put on growth, you may end up with weak broccoli. 

Mistake 4: Planting in the Wrong Spot

Choose a spot with sun, rich soil, good drainage, and water for healthy, productive plants.

Choosing the right location is paramount to success in growing any vegetable or plant, for that matter. If they don’t get the right amount of sunlight, the right type of soil, the right amount of water, and proper drainage, you’re not going to get the best performance. Broccoli is no exception to this. 

Broccoli needs a lot of sun exposure, at least six hours per day, to thrive. In warmer climates, it’s best to give them afternoon shade to extend the season. Afternoon exposure is hotter and more intense and will shorten the life of your plants.

For the best results, bulk up your soil with plenty of organic material. This is a heavy feeder, so if it doesn’t get adequate nutrients, it won’t perform nearly as well. Make sure your soil drains well and has a slightly acidic to neutral pH.

Mistake 5: Neglecting to Fertilize

Heavy feeders need steady nutrients, or they’ll languish and produce disappointing, lower-quality yields at harvest.

As I mentioned above, broccoli is a heavy feeder, and it is a mistake to leave it without sufficient nutrients. It requires a strong and steady supply of specific nutrients to perform and produce. If they don’t get what they need, you can expect your plants to languish and produce a sub-par harvest.

Mistake 6: Planting With The Wrong Neighbors

Marigolds are great companions because they don’t compete for nutrients and support healthy plant growth.

Another issue with heavy feeders is that they make complicated neighbors. If you plant them too close to other plants that need a substantial amount of nutrients, they will compete, and neither will thrive as it should. You could end up with a lousy yield from both, which is always disappointing. 

Mistake 7: Ignoring Pests

Pests like cabbageworms, webworms, flea beetles, and maggots target these plants and can quickly destroy crops.

As much as we like to eat this vegetable, there certainly are a lot of pests that also like to dine on its leaves and flowers. It is a big mistake to leave your broccoli unprotected. Aphids, of course, are a common garden nuisance that may come after your broccoli. Armyworm and cabbage looper larvae will defoliate a plant quickly. 

Because it is in the same family as cabbage, all the usual cabbage pests apply. Cabbageworms, webworms, and root maggots are all concerns. Flea beetles can be a major issue, too. Overall, there are a host of insects that can affect your plants, and they can ruin your crop in short order. 

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