May

By the month of May, most of our vegetable and flower transplants have been set out, as well as our warm-season container plants, leaving the greenhouse fairly empty. This is a great time to reset and clean out your greenhouse for mid and late summer seed and cutting culture. Open all the doors and windows to allow some fresh air to flow through. Pull out any shelving or tables if they are not permanently installed and sweep out any debris or loose soil. Check the greenhouse for wasp nests or any other pests that may be harmful to plants. Fill a clean sprayer with a 10% bleach solution and spray down the walls and surfaces to sanitize any lingering disease pathogens. Be sure avoid windy days for this task to prevent drift to nearby plants. Once sanitized, return the tables and shelves back to the greenhouse, creating some shady lower spots for placing cuttings, and mid-level full sunny spots for seed germination. May is a great time to start a second crop of heat-loving bedding plants like zinnias, marigolds, rose moss, salvia and periwinkles to extend the blooming season.

Start a second crop of zinnias, rose moss, and periwinkles in May to extend the blooming season.

June

It’s time to start thinking about our cool-season bedding plants. In June? Why so early? With a greenhouse, we can get a big head start on fall bedding plants like pansies, snapdragons, dianthus, petunias and even geraniums. If you have never tried your hand at starting cool-season bedding plants, this is a great time to experiment. Start shopping with your favorite online seed suppliers and try some new varieties that catch your eye. All the above listed bedding plants are relatively easy to start from seed. By purchasing your seed early, you will have a good selection while avoiding stock shortages and will be right on schedule for starting your cool-season garden indoors. June is also a great time to take garden cuttings of easy-to-propagate annuals and perennials like coleus, sweet potato vine, begonia, torenia, geranium, dusty miller, salvia, chrysanthemum, lantana, verbena, gaura, buddleia, scaevola and sedum. If your house plants are looking a little overgrown, you can also take cuttings from things like pothos, croton, purple heart, arrowhead, philodendron, dracaena and dieffenbachia. If your herbs are well established, rosemary, basil, mint, stevia, lavender and sage are all fairly easy to root from cuttings. Place cuttings in moist potting soil and place on a lower, shadier level of your greenhouse out of direct sunlight. Cuttings will root faster in the warm, moist environment of your greenhouse as opposed to a sunny window or low-light patio. And if established enough, your cuttings will be ready to plant in the fall. A good rule of thumb to follow with greenhouse cuttings is to leave them and forget about them to some degree. Keep the cuttings moist, never allowing them to fully dry out, but otherwise simply leave them to do their thing while the cuttings recover and start the process of root formation. The use of rooting hormone will aid in the process.

Dusty miller cuttings can be taken in summer for fall planting.

July

Start your cool-season flowers, vegetables and herb seeds for a head start on fall planting. For flowers, start seed of pansies, violas, petunias, sweet William, calendula, nasturtium and snapdragon. For vegetables, start broccoli, Brussels sprouts, cabbage, cauliflower, Swiss chard and fall tomatoes. Cool-season herbs to start in July include dill, cilantro, rosemary, parsley, sage, mint, lemon balm, oregano, chives and thyme. Starting your cool-season crops in July will give your transplants plenty of time to grow and be of good size in time for fall planting dates. July is also a great time to take softwood cuttings of your favorite pass-along plants like confederate rose, hydrangea, perennial hibiscus, lilac chaste tree, angel’s trumpet, roses, beautyberry, althea and bee balm. Treat these cuttings the same as your June cuttings, and you should have some nice transplants in time for fall plant swaps.

A summer start of pansies for fall planting.

Throughout the summer months, it is recommended to keep doors, windows and vents open to prevent the greenhouse from overheating. Inside temperatures can reach well over 120 F if the greenhouse is not properly ventilated during summer months, creating an environment far too hot and humid that will smother your plants. Only take cuttings from pest-free and disease-free plants and always sanitize surfaces and containers before use. The greenhouse is also a great place to sterilize old potting soil for reuse. Place used potting soil in a plastic storage tote with a lid, and leave in the greenhouse for several weeks, opening occasionally to stir and rotate the soil. This solarizing effect will sterilize the soil of any pests or pathogens. This process will also break down the soil a good bit. Replenish your newly sterilized soil with compost or slow-release fertilizer.

Whether you’re new to owning a greenhouse or have been thinking of purchasing one, remember to start small and learn as you go. There are many universal best management practices for greenhouse culture to follow, but often the best way to learn is to just jump in and get your feet wet. Smaller hobby greenhouses are fun to own and operate and are great starters for those wanting to learn and expand their gardening capacity. Hobby greenhouses are easy to set up and can be purchased through many online retailers and big box stores. Place in a full-sun area, running north to south with the broadsides facing east and west, and secure well with metal posts and zip ties or twine at each corner. The greenhouse canopy will have excess length on all sides that can be further secured to the ground with stakes, sandbags, landscape timbers or cinder blocks. Securing your greenhouse is crucial for success, especially in Louisiana with hurricane season upon us and severe weather season next spring. High winds can turn an improperly secured greenhouse into an oversized kite. Nothing is more heartbreaking than watching your plants and hard work get scattered to the wind. Follow these recommendations, and your hobby greenhouse journey will be off to a great start.