Garden Vegetables – How to Know Exactly When to Plant and Harvest Them

Garden Vegetables – How to Know Exactly When to Plant and Harvest Them

You don’t have to rely upon the vague seed harvesting times predicted on seed packets. They’re based upon an ‘average’ garden. Your garden is not average. Your plants will mature at different times from the same plants in the next county, or even garden.

Solution? Try this clever gardening tip to grow more vegetables. Measure the Heat Units (HUs)!

HUs are one way that commercial growers know exactly when to roll out the harvesting machines. Do they read seed packets? No. We can easily use their method too. All we have to do is keep a detailed log every year of how much heat our plants get in a given area. These records will be different for every garden and every crop.

Keeping a garden log is the first step

The first thing you do is set a Base Temperature and thereafter take note of the average temperatures each day. For cool-season crops like lettuce and brassica, fix the Base Temperature at 40oF. For warm weather crops – like tomatoes, beans, squash, sweet corn – set it at 55oF.

The base temperature is not critical. It’s just an arbitrary reference point. But whatever it is, it must remain uniform in all subsequent measurements you make, so that you can keep and compare meaningful records. Now calculate your HUs.

On the day you sow a crop outdoors, record the daily high temperature and the daily low. Add them and divide them in half. Now you have an average temperature. Subtract the base temperature from this number to obtain the HUs for that particular day.

How to know when to pick organic garden vegetables

Let’s imagine you have planted tomatoes in early summer. On day one the temperature is 70ºF at its height and 60ºF at its lowest point. The average is therefore 65ºF. Take away the Base Temperature 55ºF you have determined for tomatoes and you’re left with 10. That’s your Heat Units for that particular day.

Some beefsteak or other late tomatoes might demand as many as 1000 HUs to ripen outdoors. Early tomatoes will need fewer than 600 HUs. But your own records over the years will tell you precisely how many HUs which crop and variety needs, in your own garden.

For example, a gardener might set out modules of Alaskan Fancy ultra-early tomatoes on 1st June, the typical day after the last frost date for a region in zone 8. From experience, s/he knows this variety needs no more than 490 HUs before the first fruit is ripe.

A big advantage of the HU system is that it lets you plan ahead. If you’re sure from your records that you can harvest, say, spinach in your garden by the end of May you’ll be able to get plants ready to replace it the moment the crop is pulled. You no longer have to rely upon the vague dates suggested on seed packets.

A lazy gardening way to check garden temperatures

Do you need to rush out each day to check the temperature? No! Hang an electronic high-low thermometer outdoors that you can read from a lounge chair in your house, using bird watchers’ binoculars. Then set up an automatic watering system. And relax. You won’t even have to step outside to crop your first tomatoes, or any other plant, until they’ve reached the desired Heat Units.

Your Heat Units will be different even from your neighbors’. Yet despite even wide temperature fluctuations, month by month, in your garden you can be fairly sure of when every crop will be ready – just by doing the math. That’s a great benefit for every busy gardener!

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