Grow three plants outdoors: Part 9: Harvesting and drying

The outdoor season is slowly approaching its fragrant finale. During September and October, plants mature and it is gradually time to start monitoring their ripeness. In today’s instalment of our outdoor growing series, we will learn how to estimate the harvest time according to the trichomes and explain the correct harvesting and drying procedure.

In the previous instalment, we looked in detail at mould on plants and how to combat it. Today, we will show you how to recognise that it is time to harvest the plants. We will also learn the harvesting procedure and how to dry the flowers correctly.

When it is time to harvest

The best time to harvest plants is at the peak of maturity, when they contain the highest levels of active compounds and terpenes. Most seed sellers state an estimated outdoor harvest time for their varieties, but this should be taken with a pinch of salt. The rate of maturation can be affected by the weather, nutrition and many other factors.

The most reliable way to estimate plant maturity is to observe glandular trichomes. These small glands on the surface of the flowers resemble a tiny mushroom with a stalk and a spherical head. The trichome heads contain the active compounds and terpenes in the form of fragrant resin.

Trichomes are best viewed with a handheld microscope or a macro lens for a camera. Immature trichomes have transparent heads. On flowers at the peak of maturity, most trichome heads are milky and cloudy. A large number of trichomes with amber-coloured heads indicates overripe plants.

Before harvesting, first check the maturity of the most developed flower clusters at the tops of the plants. If they appear mature, check the flowers on the lower levels as well before starting the harvest. If they are not yet mature and the weather allows, harvest only the mature tops and leave the rest of the plant to mature for another week or two.

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How to prepare for the harvest

It is best to start harvesting in the late morning, as soon as the plants have dried after the morning dew. It is a good idea to create a truly comfortable place to sit. If your harvest has been successful, you will have at least several hours of work with scissors ahead of you. 

Scissors: Proper gardening scissors with a thin tip are absolutely essential when harvesting outdoor plants. If you decide to replace them with ordinary paper scissors, you will probably end up with finger cramps and a pile of untrimmed material.

Gloves: Working with fingers covered in resin is not very pleasant. Thin disposable gloves are best for harvesting, as they make trimming easy. Gardening gloves are usually too thick for delicate work.

Trim container: Cleaning flower clusters of leaves can be a long and arduous task. You will need sufficient light, a comfortable place to sit and a container to catch the trimmed leaves. We recommend trimming trays that sit comfortably on your knees, so you do not have to hunch over while working.

Drying nets: After harvesting, there will always be a pile of trimmings and small flowers that cannot be hung up by their stems and dried. It is useful to have several drying nets ready for this purpose. You can also dry large leaves on them.

Pure alcohol: Pure alcohol or a similar organic degreaser is best for cleaning resin from tools and surfaces. First, thoroughly grease resin-covered hands and nails with vegetable oil, then wash them with warm water and soap.

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Harvesting procedure

Although some growers harvest their plants all at once, it is more practical for most people to do it gradually. If you “fell” a large outdoor plant in one go, the leaves will become limp after a few minutes and will be more difficult to trim.

The most efficient method is to gradually remove individual branches from the plants and immediately strip off the largest leaves. Scissors are often not even necessary; simply tear the leaf off against the direction of growth. You can leave smaller leaves on the flowers and remove them after drying (dry trim), or trim them straight away (wet trim).

Hang the stripped branches on strings in a dry, airy and dark place. Light degrades the active compounds and gives the dried material an unpleasant straw-like taste.

CAUTION: If you find clumps of grey mould on the flower clusters while harvesting, take care. Carefully inspect every harvested flower, especially the largest ones, which may rot from the inside. Throw away damaged parts of the plants and disinfect the scissors.

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Correct drying

To achieve a smooth flavour and preserve the aroma, the flowers must not be dried too slowly or too quickly. The ideal drying time is between 7 and 21 days, depending on the conditions. Check the flowers every day throughout the drying period.

The optimum relative humidity for drying is 50 to 55 %, and it should never exceed 65 %. An air dehumidifier may be useful, but make sure that warm air is not blowing directly onto the flowers. The temperature during drying should not exceed 20 °C or fall below 16 °C. The cooler it is, the more slowly the flowers will dry. 

Properly dried flowers are dry to the touch, slightly springy when pressed and can be easily separated from the main stem. If the flower clusters crumble between your fingers, they are too dry.

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