So much to do, so many hot days
We all have To-Do lists for our growing spaces and it's hard to get the motivation to work out in the heat. Just like you, your orchids are waiting for a reprieve from the hot weather too. Overly warm days combined with night temperatures that stay in the upper 70's can contribute to a number of problems in your greenhouse or growing space. Which means high temperatures or not, you have to keep an eye out for certain issues.
Let's Dive Into Some of the Most Common Issues You Might Encounter
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The one I get asked about most often. High temps can cause 'bolting' on growths that mature during the summer months. Bolting, just like with vegetables in the garden, can lead to overly lush, green soft foliage and weak stems (and the occasional giant zucchini squash). The foliage simply can not hold itself up and the leaning can lead to permanently bent or broken pseudobulbs. Make sure you have greatly reduced your nitrogen levels in any fertilizer you are using. By now most orchids have matured, or nearly matured their growths for the season. Plants will continue to use nitrogen they have stored and you can slow or stop applications for the time being. Instead, switch to a low nitrogen fertilizer like Growmore 6-30-30. This is listed as a bloom booster, but the low nitrogen levels also encourages better growth during the late summer and fall months. The phosphorous and potassium also prepares plants like Phalaenopsis and Cymbidiums for winter blooming cycles. Use of Cal-Mag fertilizers is also suggested as calcium levels deplete over time and can cause premature browning or blacking of new growths.
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You will also notice that insect problems can quickly reach unmanageable proportions in the hottest months. That is because insect populations can mature much faster in the heat and longer days. During 70° days, a population of thrips can mature in about 7 days. When the temps reach over 90°, it can reduce that by half. Thrips, scale, mealybugs all grow much faster (and eat more) during hot weather. Start by adding Yellow Monitoring Cards to your growing space, both at plant level and above the benches. Not only do they catch any fungus gnats hanging around, the cards will help check for other flying insects like aphids, thrips and whiteflies. For scale and mealy bugs closely observe the plants and in the crevices. Consider using a systemic insecticide like Imidacloprid to keep populations in check. We suggest using this every week for at least three weeks to help knock down current populations and build insecticide levels in the plants themselves. Always make sure to use chemicals in a well ventilated area and to wear proper protection.
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Not only do the orchids and other plants grow but the weeds do too. Unwanted plants can quickly invade your growing space from outdoors, or from new acquisitions. Even if you can't pull every weed, try to get sporing fronds, seed pods and blooms so they can't reproduce quickly. Remember that weeds and groundcover plants under benches will also host those insects we mentioned above.
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And last but not least, many of us are in the middle of seasonal rainy weather. It seems like all across the Southeast can expect frequent cloud bursts and rolling thunderstorms that drop loads of rain on our outdoor plants. Make sure that plants in pots are not staying overly wet. The last thing you need is to fight root or crown rot in your collection. Keep them elevated and off the ground away from puddles (and slugs). If you start seeing foliage issues from the extreme humidity and rain, consider an application of a systemic fungicide like Thiomyl. This will provide a few months protection from most foliar issues and rots, especially as the weather starts cooling. Which will be soon, we hope.
- Happy Growing!
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