This is the fifth in a twelve part series for new gardeners. If you have never planted vegetables before but always wanted to, this is the series for you. Robin, who writes the blog Vegetable Matter, and I will post on the first of every month. Robin lives in Houston and I live in Boston. We will be posting about what to do in the garden that month and giving advice. So if you have always wanted that vegetable garden, but didn’t know where to start, you have no excuse. Get growing!
In New England April brings warmer weather. The ground is unfrozen and warming up fast, but we still have a chance of freezes and snow. Only plants that can stand some frost can be planted out now. There are a wide variety of crops that prefer to grow in the cool weather of spring. Last month we planted spinach and peas which can even handle some of the hard freezes. This month we start to plant things that can handle the milder frost.
Common cool weather crops good for planting in April in Southern New England are carrots, radishes, beets, Swiss chard, potatoes, cabbage, broccoli. onions and lettuce. This month I'll be talking about plants in the Brassica genus which include a lot of common and uncommonly grown plants. Plants in this genus are commonly called brassicas, cole crops, or sometimes even crucifers. These include most of the Asian greens, cabbage, broccoli, cauliflower, mustards, kale, Brussels sprouts, collards, kohlrabi, and turnips. They all prefer approximately the same conditions and treatment. They vary a bit, but not enough to worry about. Most of these plants grow as well or better in the fall as in the spring.
Your soil is very important to growing brassicas. Mineral deficiencies are common if the soil pH is too high, but brassicas don't like soil with a low pH, so you have to make sure it is in the right range. Brassicas do well in with the soil pH in a range between 6 and 7. Though 6.5-7 is often better. Fall is the best time to lime to bring up the pH of the soil, but I've done it right before planting some years. The plants do just fine.
Brassicas also do best with a high percentage of organic matter in the soil to make the nitrogen more available in a cold spring. So add lots of compost. All plants need compost, but brassicas do especially well if they have a lot.
They are heavy feeders, which means they ought to be fertilized before planting and again about halfway through their growth for the longer maturing ones. The midway fertilization is called side dressing. The fertilizer is sprinkled over the surface of the soil in a circle around the plant and scratched very shallowly in. You should not place this fertilizer near the plant stem, but toward the outer leaves of the plant. A slow releasing fertilizer is best. Cole crops have a very shallow root system and if you give them a large dose of immediately available nitrogen it could burn their roots. Most organic fertilizers are slow release by nature, but blood meal is an exception. It can burn roots if applied too heavily. Cotton seed meal should also be avoided as cotton is not an edible and is grown with some very nasty pesticides.
A good rule of thumb for planting is two weeks before your average last frost. I sometimes plant earlier because I always grow them under row covers which give them protection from a freeze. Brassicas can handle a bit of cold weather and frost, but it is best that they don't see hard freezes because some will bolt prematurely in the spring. Asian greens seem to be very susceptible to this. Don't despair if your Asian greens start to bolt though. The flower stalks are often very good and on many, the leaves are still good to cook with. Think of the flower stalk as a bonus. If you do want to grow good heading Asian greens (like pac choi and Napa cabbage), fall is a much easier season to grow them as they won't bolt then.
Except for the root crops like turnips, brassicas are generally put in the garden as transplants here and not seeds. Transplants can be grown indoors under lights or bought at a nursery. Whoever grows them, the transplants have been coddled for a long time. The plants are not hardy enough to go straight out into the garden. If you put them right into the garden they could languish, get sunburnt or the worst case, they could die. To avoid transplant shock you should harden all seedlings off before planting them. This gets the seedlings used to the environment slowly. The first day you might put the plant outside in direct sun for an hour, then bring them back inside under lights or under partial shade. At night they get brought in to start with. Then slowly increase the time in the sun. After about five days they should be in the sun all day long and outside at night provided no freezes are forecast. After a week they should be transplanted.
Now I have a confession to make. I don't always do this. If I think bought plants have been outside for a while I will cut down on the time. You don't always know and the plants can suffer if you miss guess. A week is much safer. My home grown plants are grown in soil blocks and I use a fan to harden up their stems inside. Transplant shock is pretty minimal for them. They still need to be hardened off however to make sure they can handle real sun instead of the much dimmer fluorescent lights. So my biggest concern is making sure they don't get sunburned by planting out too quickly. You know you have sunburnt your plants if you find white patches on the upper leaves. The plant will survive, but it won't grow quite as well at the start.
So now you are ready to plant. Dig a small hole in your fertilized bed and put the plant so the soil surface will be the same height as it is in the pot. Many brassicas can get away with being planted a bit deeper. Some plants will rot if you do that, but brassicas seem to survive that alright. Water the plant in well. Then keep it watered so the soil doesn't dry out.
I've never experienced any diseases with brassicas. Club root is a possible disease. It doesn't live well if the soil is over a pH of 7, so many over lime that part of the garden. The issue with this is that boron (and other minerals if you bring it even higher) becomes less available to the plant. You might need to foliar spray the plant with boron if you use this approach. Many with the disease in their soil will rotate their crops on a long schedule. Five to seven years is a normal rotation schedule if you have this problem. If you do rotations, make sure not to reinfect other parts of the garden by not cleaning off your shovels after digging in the brassica bed. My brassica rotation schedule even though I've never had problems is six years.
My biggest problem with brassicas are the insect pests. I have four major pests in my area. Root maggots are flies that lay eggs in the soil around the base of the plant. The little larvae live in the soil eating all the roots. You will typically not notice the insects themselves, but when your brassicas start to wilt and they have been recently watered, you can bet it is root maggots. If you take the plant out you will notice that it doesn't have much of a root system left. They are most problematic on small seedlings. A large plant can often survive a mild attack.
The next insect pest is the flee beetle. It is a small beetle that jumps when you bring your hand close. They look like small little black dots. These can have several generations in a year. The larvae feed on the roots of the plants, but do minimal damage. The major damage is caused by the adult beetle. They may be small but if there are enough of them they can chew up the leaves and can kill seedlings. Larger plants are not as badly affected.
The third insect pest is the caterpillar. There is more than one type of caterpillar that feeds on brassicas, but these can totally strip the leaves from the plants if there are enough. In addition they can get into the heads of broccoli and make it pretty disgusting to eat as you often can't see these pests as you pick the head.
I'll get to the last pest, but first I'll talk about control of the first three. If you put on a row cover, like a light weight Agribon right when you plant and keep the edges tacked down well, it will prevent most of the damage. I find I'm not perfect and occasionally get a little root maggot or caterpillar damage, but very little. If you don't want to row cover your garden and don't want to spray toxic chemicals, flee beetles can be vacuumed off of plants. More will find you, but it keeps the population down. One beetle does not do a lot of damage. Root maggots need to be able to get to the soil surface near the stem to lay their eggs. Many people use paper collars around the plants so the fly can't reach the soil surface. Caterpillars can be killed by spraying with Bacillus Thuringiensis. This is a bacteria that infects only caterpillars. All other insects and animals are not affected. Make sure you get the kind that targets caterpillars since there are strains sold that affect only mosquitoes and black flies.
The last insect pest is my nemesis, the slug. People who live in dry areas of the country tend not to have these, but here in the northeast we have lots and row covers will not keep them out. They can crawl right under them. They can eat direct seeded brassicas before you ever get to see the seeds come up. This is why I always use transplants with brassicas. They are a slug's favorite food and will be drawn in from any nearby lawn or wood. They can quickly eat any transplants too if you don't protect them. There are many ways I've tried to keep slugs out of the garden: beer traps (I have teatotaling slugs), diatomaceous earth (slows them down but they still eat the plants and has to be applied after every rain), crushed eggshells (helps, but still only slows them down a bit), and handpicking at night with a flashlight (works the best of the above, but what a pain). This year I'm going to try iron phosphate (sold under the brand name Sluggo). Iron phosphate is an innocuous substance where pets and humans are concerned and both iron and phosphorous are good for your plants. I've heard very good things about it.
I hope I haven't scared you off with respect to brassicas. They are not the easiest of garden plants to grow, but they are extremely productive in a small space and you can get at least two crops out of that space. One in the spring and once that one is harvested you can put in the fall crop. Fall is an easier season for them as often some of their insect pests have found other hosts already (caterpillars and slugs will always be an issue) and bolting is not an issue..
Other post in the seriesDetermining your growing zone and planting peas (Vegetable Matter - December)
Planning a Garden (Daphne's Dandelions - December)
Growing Lettuce (Vegetable Matter - January)
Starting transplants indoors (Daphne's Dandelions - January)
Growing tomatoes (Vegetable Matter - February)
Compost (Daphne's Dandelions - February)
Snap Beans (Vegetable Matter - March)
Peas and Spinach (Daphne's Dandelions - March)
Eggplant (Vegetable Matter - April)
Brassicas (Broccoli, Cabbage, Asian vegetables) (Daphne's Dandelions - April)
Edamame (Vegetable Matter - May)
Tomatoes (Daphne's Dandelions - May)