|Above: Onion maggot and carrot rust fly damage that can be avoided in a number of non-chemical ways. Below: Jim Harris’s vegetable garden on nearby Protection Island: his remay-cloth-covered carrots and beets; his huge onions; and his veggie garden gate sign. Author photos. |
Two weeks ago (April 17) I wrote about a virtually unheard-of technique—that of grafting tomato plants which has proven (at least on the named cultivars) to produce heavier crops of tomatoes.
This week I want to start off on vegetables again—this time on something that applies to a fairly large selection of different veggies. It’s called succession planting—not something new at all, but something that far more gardeners should practice, at least on some crops.
The easiest way to accomplish successive plantings is to plant multiple cultivars with different days to maturity. Your seed catalogue will give you the estimated days to maturity for each cultivar. If you start them all at the same time, they will naturally stagger themselves over a longer period. If you purchase your veggie seeds from Johnny’s in the U.S., let’s take broccoli as the example. Johnny's broccoli varieties range from 49 to 68 days to maturity. Plant ‘Blue Wind’, ‘Bay Meadows’, and ‘Diplomat’ at the same time and you will be harvesting broccoli for three weeks.
A second approach is to make successive plantings of the same crop cultivar. The timing between plantings should be approximately the same as the expected "picking window" during which the crop is fully productive.
One of the staff members at Johnny’s Selected Seeds in Maine, drew up a list of suggested repeat planting intervals for a large number of veggies. Here are the recommendations. Green beans - every 10 days, Beets - every 14 days, Cucumbers - every 3 weeks, Kale/Collards - every 3 weeks, Lettuce - full size every 10-14 days, Lettuce - salad mix every 7-10 days and harvest re-growth [seed will not germinate reliably above 26C/80F soil temperature, limiting mid-summer plantings], Melons - every 3 weeks and multiple varieties, Radish - every 7 days, Spinach - every 7 days and harvest re-growth [seed will not germinate reliably above 26C/80F soil temperature, limiting mid-summer plantings], Summer Squash - every 6 weeks (or more frequently if vine borers are prevalent), Sweet Corn - every 10 days and multiple varieties, Carrots - often planted early May for summer and again early July for fall harvest, Cabbage/Cauliflower/Broccoli are often transplanted early May for summer and trans-planted again early July for fall harvest.
Thanks to the folks at Johnny’s Selected Seeds for the forgoing list.
A concern of many vegetable gardeners, especially those new to growing veggies, is the great disappointment at digging up your first onions and seeing them literally riddled with holes, and many small worms within the bulb or root. Those are onion maggots, and many folks now have a similar problem with carrots; wherein the carrots are badly damaged upon harvesting. Both of these problems result from similar maggot insects (respectively, Delia antiqua and Psila rosae) and there are a few ways to protect your crop from damage now that the former prime way of preventing damage is not available to us any more—that was the application of granular Diazinon to the soil at the time the seed (or young onion bulbs/sets) were planted.
Though I am often not too convinced with some so-called “organic gardening advice” [because it often simply does not work], organic gardeners do offer some suggestions which can work if the ideas are followed to the letter. For example, yellow sticky traps and Tanglefoot are two good mechanical ways of stopping onion maggots in their tracks. Also, floating row covers (plastic tunnels) crop rotation, not planting early when the maggots are most active, and ensuring that all old culls of onion are cleaned out of the garden at the end of the season will all help.
As to carrot rust fly, the floating row covers, eliminating the first early-season planting and crop rotation as well as yellow sticky traps will certainly work well with them as well.
There are almost as many techniques and variations of technique in using the floating row covers as there are experienced vegetable growers (amateur and professional) who use them. There are also a wide variety of materials in use, including something called remay cloth (available from Lee Valley Tools, both on the Web and their retail stores) which is what Jim Harris on nearby Protection Island uses and a couple of photos of his outstanding vegetable garden accompany this item. Jim grows many of his vulnerable (to insects) vegetables under remay. In mid-August when we were there he had carrots, Swiss chard, beets, and radish there and had already harvested his turnips and others. He likes to keep his use of remay simple and uses no hoops to hold the remay up above the veggies, rather he just leaves it very loose before holding down the sides with soil or boards as shown.
You might ask how do row covers work. To understand that, you need to know a bit about how the maggots ‘work’.
Shiny-green, yellow-headed flies (6 mm) lay eggs on the soil surface near plants in late spring, early summer. The emerging larvae (maggots) dig down and attack tender roots. They pupate in the soil and emerge as adults in August or September. These mate and lay eggs which hatch into larvae that over-winter in the soil or in the roots (they are found in stored carrots).
The one characteristic these pests have in common is that the initial contact is made by the adult fly. The ‘old’ idea of putting the granular Diazinon into the soil was to get it into the area where the roots would develop and thus it would kill the larvae before they could do any damage to the roots.
One of the prime methods of preventing attack is moving the plantings of these vegetables to entirely different sections of the garden each year. Then, there are no lingering larvae to infest the young plants. However, that is often virtually impossible in small home gardens.
Remay should be applied over each row immediately after seeding, or planting of young transplants. The width of each row cover should be about 45 - 60 cm (18 - 24”) and the edges should be held down with soil to prevent the insects getting into the planted area. Ideally, each row cover should be slightly hooped up using flexible branches or the like (so that there is a clearance of about 15 cm at the row centre to allow the plants to grow), but even if the material is flat on the ground with lots of spare material to allow the young plants to push it up as they grow (that is Jim Harris’s method), the row covers should work well. They can be removed after about three or four weeks.
Keep in mind that cheesecloth does allow penetration of full light and rain or irrigation. By the way, if you can-not find (or afford) remay cloth, you could use old sheer window curtains!
So, again, Happy Gardening!