The success rate in the grafting of some tropical plants can be rather low, unless suitable grafting aids are used. One such useful aid is the steam tent, e.g. when Longans, Jakfruit or similar types of plants are to be grafted. The steam tent creates a humid but not a wet environment.

1. The Steam Tent
The size of the tent can vary. A good size would be 1.5m length, 1m width and a height of about 1.2m. The steam tent usually has a triangle shape, but in special circumstances a tent of round or rectangle shape is just as good.

As a base, a sort of tray should be used. The tray can be filled with sand or sawdust or peat moss. The tent frame can be made out of 6-7 mm steel rods. As a tent frame cover, a 200 micron (or thicker), clear plastic sheet can be used. The fixation of plastic sheet to the tent frame can be through a wide sticky-tape. Inside the tent 2 irrigation positions, preferably overhead, should exist. Each should be equipped with a mister head. The valve to control the operation of the misters should be outside the tent (see Picture 1).

2. Climatic Conditions in the Steam Tent
The climatic conditions in the steam tent must be observed daily. If sand has been used to fill the tray, and the outside temperatures are high, daily watering for about 4-5 minutes may be necessary. A rough guide for the right humidity in the steam tent is that on the clear plastic, on the inside of the tent, a high amount of water drops are visible.

Because of the overhead misting system, the grafts on the plants in the steam tent should be wrapped with pancofilm grafting tape. This grafting tape is usually water-tight if applied properly.

Sketch of Steam Tent

The temperature in the steam tent should not rise above 28-30°C. If the outside temperature is very high, such conditions can only be achieved if the steam tent is put into a room with some sort of cooling.

A greenhouse covered with glass or rigid plastic sheets approximately 2.0m long, 2.0m wide and 2.0m high, equipped with a suitable air conditioner (some shading may also be needed) would be the best solution for a commercial-type nursery, only so the temperature in the steam tent can be controlled as required.

For some tropical plants the steam tent is essential if the outside conditions are not favourable. For others it is a worthwhile aid.

Walter Kuppelwieser
Extract from Mossman Digest No.6 Dec. '86

DATE: July 1988

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