GROWING VEGETABLES IN RAISED BED GARDENS AND CONTAINERS
Containers such as pots, grow bags and large plastic bags are also in fact raised beds, just smaller versions of them.
They make successful growing of tomatoes and potatoes a real possibility and because the feeding and watering is directed at a few plants only the crops can be massive.
Potatoes will also grow in traditional raised beds but you may loose some of the potatoes growing near the surface. Normally you would earth up potatoes to protect the top ones from the light. However, in a raised bed the ridges may get blown away or simply crumble because of the light structure of the soil. We therefore recommend growing potatoes in large pots or specially made plastic containers.
Root vegetables such as carrots, parsnips and turnips are ideal for raised beds, just make sure the bed is deep enough for the roots. Growing carrots in raised beds will banish forked roots forever. That, combined with easy protection from carrot fly, makes growing carrots much easier.
Our current list of vegetables which are ideal for raised beds and other containers is:
The easiest way to start off with raised beds is to buy pre-cut and pre-drilled kits. To start off we recommend that you buy a cheap kit, if the raised bed gardening bug bites you after that you can easily add another more expensive kit. These are quickly assembled and most require only the most basic of tools. Click here for our raised garden beds comparison page.
Most vegetables will do very well if you fill the raised bed with two thirds potting compost and a third garden soil. If you can't get hold of garden soil then John Innes will do just as well. This may sound a bit expensive but the soil will last for ever only needing the occasional top up. Add as much well-rotted garden compost as you can spare.
General purpose potting compost can also be used by itself and this is the best solution containers. The advantage of adding garden soil to a raised bed garden is that it adds some "body" to the soil, allowing you to grow taller vegetables which require some support.
A commonly asked question when starting off a raised bed is "can I simply pile the compost on top of grass". I most case this will be OK as long as the depth of soil is at least 15cm / 6in above the grass. The compost will simply smother the grass and prevent light getting to it and thus killing it. The grass will then compost down.
A better approach though would be to scrape the top 3cm / 1in of grass / soil from the surface and turn it over. This will kill the grass sooner and allow it to compost sooner giving your vegetables valuable nutrients. This method is also more likely to kill any perennial weeds on the site. The final method is to place a weed proof membrane on the surface of the grass before adding the compost. Just make sure it will let water drain. Three or four layers of newspaper will have a very similar effect and of course be much cheaper than a shop bought alternative.
Raised beds and containers drain very well and this can be a double-edged sword. The good side is that they will not get water-logged but the downside is that they loose water quickly and need frequent watering. If you are growing vegetables in raised beds then keep a watch on them in warm weather and water as required.
A mulch over the top of the soil will significantly reduce the need for watering. Chipped bark makes an ideal and attractive mulch when spread about 3cm (1žin) thick over the surface. Spread it so that it's near growing plants but not touching them.
Black plastic is a cheaper alternative. It doesn't look as attractive as chipped bark but reduces the need for watering just as well. Simply cut it into appropriately sized strips and place it between rows of plants. Hold it in place with a thin layer of soil.
Our one page raised bed vegetable calendar recommends using two types of fertiliser in your raised beds and containers. The first is a long lasting organic fertiliser such as blood, fish and bone or bonemeal. These are readily available from all garden centres in powder form.
To apply this fertiliser sprinkle two or three handfuls over the soil surface per square metre / yard. Then work it into the surface of the soil with a trowel. Blood, fish and bone breaks releases only small amounts of nutrients in the soil but it does it consistently over a long period of time. It also has a wide range of nutrients, some of which are not found in general purpose fertiliser.
We suggest an application of blood, fish and bone in late February and then again in mid July.
The second type of fertiliser is a general purpose fertiliser which comes in two forms, liquid and granules. The granules are often called "Growmore" whilst the liquid is sold under a variety of brand names. For raised beds we strongly suggest you use only the liquid general purpose fertiliser. The granules are difficult to distribute evenly in a crowded raised bed and can cause burning if they come into contact with a plant.
General purpose fertiliser contains three essentials to plant growth, nitrogen, phosphorous and potassium. It should also contain a range of trace elements.
When growing vegetables in raised beds and containers they are normally spaced very close to each other. This requires the soil to be fed at more regular intervals compared to open ground. We recommend a weekly feed with general purpose fertiliser starting in late March and finishing in mid September.
The feeding suggestions above will supply all vegetables with a reasonable amount of nutrients. Specific vegetables however do have different needs. If you have a very large raised bed (or have lots of one particular vegetable) you may be able to successfully feed specific vegetables differently. Below we give you the feeding needs of each vegetable.
No specific feeding requirements, stick to our suggest feeding advice above.
Replace liquid general purpose fertiliser with a tomato liquid fertiliser for better root growth.
No specific feeding requirements, stick to our suggest feeding advice above.
Lettuce do not benefit from too much feed, it can cause the leaves to overgrow. So, if possible, reduce the the liquid general purpose feeding from once a week to once a month. The twice yearly feed of blood, fish and bone will provide the majority of nutrients a lettuce plant needs.
The normal feeding regime up to mid July is fine. From then on onions will do best if they are not fed with general purpose fertiliser. Reducing the feed at this time will help stop the foliage growing too much and will also firm up the onion bulb which will help them store for longer over winter.
No specific feeding requirements, stick to our suggest feeding advice above. Radish tolerate lack of feeding better than most vegetables.
We suggest growing potatoes in their own containers. The best feeding regime for potatoes is a feed of liquid tomato fertiliser every two weeks.
All the normal rules for pest control apply when raising vegetables in raised beds and containers. However, protecting vegetables in raised beds from flying insect pests is especially easy. Drive a wooden post into each corner of the bed and drape protective light weight horticultural fleece over them to cover the bed. If the corner posts of the raised beds are already higher than the bed then it's even easier.
Covering containers is not so easy but horticultural fleece can be draped over the growing vegetables at crucial times of the year.
Vegetables grown in raised beds can be grown much closer together compared to those in the open ground. Make sure that they are well fed with a general purpose fertiliser to support the dense, quicker growth.
Because the soil in a raised bed and containers is higher than the surrounding soil it will heat up quicker in the spring. Combining this with good soil and a protective fleece will enable you to sow seed a good two to three weeks earlier than normal.
At the end of the season, cover the raised bed again with either clear plastic, corrugated plastic or even protective insect fabric. All of these will help to retain heat and extend the growing season by a few weeks.
END OF ARTICLE
(see top of page tabs for more related articles)
READER COMMENTS AND QUESTIONS ABOUT THIS PAGE
WEEKLY DIARY NAVIGATION
Click on any number to go to that weekly diary entry for the month.