Veggie Gardening 201
Taking Your HomeGarden to New Heights
Phil Hannay, Trumpeter Swan Farm, Buffalo, MN
Wright County Master Gardeners Spring Days Education
March 12, 2011
St Michael - AlbertvilleMiddle School
Minnesota gardeners have many advantages including ample moisture, decent soils, reduced bug and mold problems, and long warm summer days. We have one big disadvantage, the short growing season. This presentation will cover some of the ways we have confronted the short growing season to hasten our harvest and then make it last as long as possible.
Warm Germination
Peas can be planted as soon as the soil can be worked. But in cold soil, the peas can take 3 weeks to emerge. In 80 degree soil, peas emerge in 5 days. Selected cold weather crops can be germinated inside on a warm table in trays of soil. After germination, those trays can be moved to the greenhouse, high tunnel or directly to the field to get a 2-3 week jump on seeds that are directly sowed.
Cool weather crops we have done this way include radish, onion sets (bulblets), leaf lettuce and snap peas. Most are planted in a 6x6 grid, but onions we do on an 8x8 grid.
Trays of germinated plants are placed directly on soil. Trays are slotted so the roots can grow thru into underlying soil. Trays act like raised beds, they are warmer than the ground, so the plants grow faster. As the plants get bigger, they continue to root into the ground which is finally warming up.
Our practice
Six foot plastic folding table with plastic sheet cover and 2 foot overhang
Oil-filled radiator underneath table
Germination bed thermostat with 115v relay and remote sensor
Plastic sheeting over trays to retain moisture and heat
Foot square 4” high slotted plastic trays to hold 3” of soil
Row Covers
Row covers serve two functions. Help prevent frost and keep in heat.
Understand frost – its caused by clear nights and low humidity. Just like a fire radiates heat, so plants radiate any heat they have in their leaves. If the night is clear, the heat is lost to outer space, and not reflected by clouds. As the leaves cool, they will condense water out of the air (like a cold glass condenses water on a summer day). Water gives up heat as it condenses and slows the cooling of the leaves. If air is humid, the dew is heavy and the cooling is slower. But as the leaves radiate more heat, they finally fall below freezing and the condensed water freezes into frost. Wind makes a difference as well. The air does not radiate heat as quickly as leaves, so air cools more slowly. A breeze will help stir up the air and keep the leaves above freezing (until the air temperature itself drops below freezing)
On a very clear, calm night, I have seen frost form when the air temperature was still 42 degrees. The plant leaves were actually 10 degrees colder than the air.
Row covers work by reflecting the heat radiating from the leaf back to the leaf, and by holding in the heat rising from the ground, further slowing the cooling. Row covers should be white or light colored (reflect heat). Clear plastic is not a good row cover as it transmits light (and heat) with little reflection.
Understand heat – plants don’t grow well below 50 degrees and they don’t grow well above 90 degrees. Chemical reaction speed doubles for every 18 degrees in warmth. So if ample sun is available, a plant will grow twice as fast at 86 degrees as it will at 68 degrees.
Your goal with row covers is to capture the sun’s heat (even on cloudy days), raising the temperature inside by 10 or 20 degrees. However, the row cover should release heat as it gets hotter so the inside temperature does not exceed 100 degrees. So a woven fabric is good, or plastic with slits in it is used by some. Plain plastic heats up too quickly to be a good row cover.
Our Practice
Use woven row covers, like Agribon
Anchor with rocks, soil or sections of steel re-rod
Monitor weather service () forecast – watch especially dew point (temperature where dew or fog starts to form) and wind speed
Humidity is often low in spring, watch out for surprise frosts
In fall, we try to evade the first frost – often a nice stretch of weather follows
Mini-raised Beds
We have build mini-raised beds using two 8 foot long 4” boards held apart by a 2” spacer. We use these for early transplants of head lettuce, spinach, kale, and broccoli.
Seeds are germinated in Jiffy-7 pots on a warm germination table. Mini-raised beds are then positioned on the ground and filled with potting soil. The transplants are planted into the potting soil.
Two advantages – the potting soil and raised beds are warmer than the underlying soil, so plant growth is faster; and watering is easier as the mini-raised bed acts like a pot, holding the water.
Our Practice
We use cheap ¼ thick 4” wide wainscoat pine boards preserved with a sealer
A 2” wide piece of cedar board at each end completes the rectangle
Grow Your Own Transplants
It’s a dirty little secret that garden center transplants have been sprayed with chemicals to stunt them (so they don’t grow too quickly) or to make them flower early. “Transplant Shock” is usually just waiting for these chemicals to wear off and the transplant resuming normal growth.
Grow your own transplants, and you can gain a week or two on garden center plants, plus have a wider selection of varieties.
Watch out for these common mistakes:
Start Too Early – plants get spindly and root bound. Two or three weeks before planting are often enough. Typically, when first true leaves are fully out, they can be transplanted.
Not Enough Light – really need to have full sun or very bright lights. A sunny window is not enough – the plants sense the darkness around them and the need to grow toward the window. You really need a cold frame or green house to surround the plants in light. You can use grow lights – but use 3 times as many as you think you need.
Not Enough Pot – plants like tomatoes need to start a bit earlier and grow larger, start in large soil blocks or transplant to larger pots to prevent them from becoming root bound.
Transplant Too Early – That first week in May, the air is warm; you want to get those tomatoes in the ground. Two problems – late frost and cold soil - your garden looks nice, but it doesn’t grow well. Wait until the soil warms. Wait until Memorial Day to transplant.
All Your Eggs in One Basket – If you can, start two sets of transplants a week apart. This will give you more protection from weather risks. If you plant transplants and a big rain flattens them, you have your next set of transplants to try the week after.
Fail To Harden - be sure to harden your plants. Glass is like sunscreen – it reduces UV rays. When possible, plants should be exposed to full sun for an hour or two a day to make them resistant to sun burn. Some wind is good as well - it makes their stems stronger.
You can transplant a lot of plants to get a 2 week jump of the season. This includes plants that you might not think of like peas, beans and corn.
Our Practice
Jiffy-7 pellets – head lettuce, spinach, kale, broccoli, cauliflower, Brussel sprouts, squash, melons
2x2x6 plant bands – tomatoes, squash, melons
128 cell trays – corn, beans, peas
Germinate on our heat table, move to our 8x10 greenhouse, on nice days move trays outside for several hours. In May, move directly from heat table to direct sun outside – keep outside unless frost threatens. (Cool sensitive plants like tomatoes and peppers stay in the greenhouse).
Succession Planting
Everyone knows what succession planting is – not planting everything at once, but planting some every week for multiple weeks. But it’s so tempting to just plant everything at once. Not only can you spread the harvest out, but you avoid the glut of produce when everything comes in at once.
Example – green beans. One or two healthy plants can have enough beans for one meal. If you want beans 3 times a week, you only need to have 6 well cared for plants per week. So think of planting just 8 seeds, each week, for 10 weeks. Think of carefully weeding 6 bean plants as they germinate, and keeping them clean and mulched.
Example – summer squash. Summer squash grow fast, produce early and are great in a garden. But after about 4 weeks of bearing, the plants start to decline. The fruit is not as consistent, the leaves are ratty and mildew sets in, the plants sprawl. Summer squash is very prolific early on, so it takes few plants. Two zucchini and two straight neck squash plants are all you need for plenty of squash. Think of transplanting 4 squash plants every 4 weeks – once in late May, once in early July, and once in early August.
A rule of thumb is to plant no more than one fourth of your garden in any one week.
Our Practice
Plant some every week – peas, beans, corn, beets, turnips, lettuce
Plant every two weeks – broccoli
Plant every four weeks – summer squash
Cold Weather Holding
Many plants will hold their produce well in the cool weather of late fall. While tomatoes become mealy and bland in the cold, peppers are just fine holding week after week. Same with green beans and summer squash - if you can keep them from freezing, they will sit happily in the field at 40 degrees for several weeks. Take advantage of this by planting twice or three times when you do the last plantings. The growth will slow in the cool fall weather, but the harvest-time will stretch out over several weeks.
And, of course, other crops are resistant to frost like broccoli and lettuce and can be harvested even after a hard freeze has occurred.
And, don’t forget the ground crops like carrots, beets and potatoes. Mulch will keep the ground from freezing, and you can get at them even after the winds of November come.
Our Practice
Beans, Beets – for the last 3 weeks (last 3 plantings), plant twice as many earlier weeks
Zucchini – last planting, four times as much, skip the straight neck squash in the last planting
Increased Productivity
We all know careful weeding will do wonders for your productivity. Here are some areas that might help as well.
Raised beds – built 2-3 feet across with 1-2 foot aisles. Put straw in the aisles for weed suppression and to make it easy on the knees. Beds warm up and dry out more quickly in spring, giving you a week or two edge over flat ground.
Mulch – most effective after mid-June when soil has warmed up, weed germination has slowed down, and moisture retention becomes important.
Right Sizing – plant less, space more. You don’t have to plant all the beans in a packet just because you have them. Be generous with the spacing. Fewer plants mean less thinning. Fewer plants mean easier weeding. Your productivity will actually increase with fewer plants due to bigger, more vigorous plants.