Building your own greenhouse

Adrian Higgins
Washington Post Gardening Columnist
Thursday, January 28, 2010; 12:00 PM

Washington Post gardening columnist Adrian Higgins was online Thursday, Jan. 28, at Noon ET to discuss how to build and maintain your own greenhouse, this week's cover story in the Local Living section. Read "A bit of Eden in your own back yard" here.

The transcript follows.


Easton, Md. -- Lovely Eastern Shore: Hello. Which month can I start to plant a spring garden of basil, tomatoes, bell peppers and cukes? I plan to start the basil indoor. Many thanks.

Adrian Higgins: Hi, everyone. Nice to be back. I've seen some bud breaks on a few plants, and I'm already getting spring fever. Each of the veggie/herbs you mention have different requirements, so I'll address each in turn.

Basil is really cold intolerant, and it bothers me to see basil plants for sale in early April or even late March to unsuspecting customers. However, you can grow basil indoors in a bright location (a warm greenhouse would be superb) and you could start a batch now for that purpose. But basil plants should not be set out in the garden until early to mid May, depending on the microclimate of your garden. Thus you shouldn't start any garden basil from seed until early to mid March. Bell peppers take forever to fruit and ripen, so it pays to have plants ready to plant out, again in mid May (no earlier, too cold). You could start them in early March. Tomatoes should be started indoors in early to mid March (not February) and cucumbers are directly sown once the soil has warmed to about 70 degrees, mid to late May.


Alexandria: No question. Just a note to say we miss your chats, Adrian.

Adrian Higgins: Oh thank you. I miss that connection too. I am doing a blog entry on vegetable gardening called Groundwork. It appears Mondays in the Food Section's blog, All We Can Eat. I am also about to enter the brave new world of tweets and twitters.


Manassas, Va. 20112: How do I find other novice local (Prince William County)greenhouse users who are interested mostly in vegetable gardeners?

Adrian Higgins: They're rather thin on the ground. I would try to hook up with members of orchid and begonia societies, and perhaps fern societies, who tend to have greenhouses. Also, both Green Spring Gardens and Brookside Gardens are involved this weekend with seed exchange events, and both are likely to attract greenhouse growers.


Silver Spring: Good afternoon. So happy to see you! I'm looking for a row of deer-resistant shrubs to be against the south side (direct hot afternoon sun)of our brick house. Height can be up to 5'. Would nandina be appropriate? Do you have another idea? Thank you so much!!

Adrian Higgins: Does anyone have experience with deer and nandina? The one great thing about nandina is that if the deer do nibble it, it is one of the most forgiving shrubs in terms of growing afresh, even from suckers. I wrote recently about winterberry hollies, which seem to be unmolested by the deer.


Asian Lady Bug Beetles?: I asked this question in Home, and was referred here as well. How can I keep these out of my kitchen? I have a window with southwestern exposure and they seem to come in from the window. Are they nesting within the walls of the house or coming in from outside? The exterior is brick, and it is a fairly warm and sunny -- we have our best overwintering of plants in the garden there. How can I keep these from coming in? Thanks!

Adrian Higgins: A number of newish pests have arrived to invade our homes in the autumn, including the Asian lady bird beetle. Others include cluster flies and the brown marmorated stink bug. The last is the most offensive, in my book, and not only shows up inside the house (and emits an odor when disturbed) but actually is a genuine garden pest, especially of fruits and veggies. The lady bird, by contrast, is of value as a beneficial insect outdoors in the growing season. It kills aphids and other pests, including those that afflict shade trees that are physically impossible to spray because they are so high in the canopy. I would vacuum the lady birds in a fresh bag, and store them in the fridge to slow their metabolism (not the freezer) and then let them out in April. If you have a honeysuckle or rose, put them on that, or even spring grown salad greens, which attract aphids even when the weather is cold.


Annandale, Va.: Hi. I have a vegetable garden really close to my neighbor's driveway. It was fine until recently they started parking their cars that far back. I believe my broccoli, peppers and beans suffered. Any ideas? Thanks.

Adrian Higgins: You don't say exactly what the problem is. If it's shade, remember that the path of the sun will change from being low and in the south, to being high and in the west (actually northwest in June). If you are worried about chemical contamination, there's not much you can do about that and you will have to move your beds. If the problem is people stepping in the garden, you can put up a fence or create raised beds. If it's road salt, you can hose the area and wash away the salt.


Manassas, Va. 20112: Is it important to get green house seeds specifically?

Adrian Higgins: No. Some seeds require cold treatment before germinating, but for most vegetable and annual seeds, germination is simply a product of moisture, soil temperature and, after germination, light.

In a cool greenhouse where night time temps are kept in the 40s (my favorite type of greenhouse by the way), you will have to create some sort of bottom heat to get seeds to germinate quickly and safely. This is done with an electric heat pad, which can be moved to the next seed tray once germination occurs. Warm season veggies such as tomatoes, peppers, cucumbers and squash need far warmer soil to germinate than cool veggies such as lettuce, radish and brassicas.


Thanks for the memory: Many, many years ago, our "eccentric" neighbor had a greenhouse built in his backyard. An endless source of fascination to us neighborhood kids, and an opportunity for a lucky few to "help out" in the greenhouse, earning a few extra dollars and much more in an education. I still love the smell of a greenhouse. Thanks for the memories.

Adrian Higgins: Thank you. I think entering a warm, moist greenhouse from a cold outdoors is one of life's exquisite moments. I remember when Tom DeBaggio had his retail houses in Arlington and going in there with his benches full of rosemary and lavender cuttings, and you can just imagine the olfactory overload. Superb.


Manassas, Va. 20112: I have read that cleaning the greenhouse with a clorox dilution is very important in the fall. Is this done in our area?

Adrian Higgins: Good sanitation is extremely important for a greenhouse because the environment is a natural haven for fungi and their spores. So an annual sanitization (if that's a word) would be important, along with the need to have a little fan going all the time to move the air.


Purcellville, Va.: On a tour of the Monticello cemetery, I was intrigued by an old poncirus (aka hardy orange or bitter orange). It was in a perfect setting, with its thorns and small orange fruit making it resemble a Halloween tree. Have you tried one in our area? I planted one this summer, but when it started to get cool this fall (long before frost), the leaves dried up and it may have died.

Adrian Higgins: The hardy orange is a long favored plant shrub, and the only hardy citrus that can be grown outdoors here. In the right setting, and massed, it is a spectacular landscape plant. The leaves drop in winter to reveal lime green stems and the most vicious thorns you can imagine. They are decorative in their own right. The fruit resembles small oranges, and is quite awful eaten out of hand, but can be used for marmalade etc. In April, the plant sets beautiful white, star like flowers with the faintest scent of citrus. Good luck with yours.


Richmond, Va.: I am so pleased that you are chatting today. Post editors, I would PAY for chats with Adrian! But, enough of the love fest. Can you recommend a dwarf fragrant bush for a partially shaded area? Would a gardenia work? If so, could you recommend a variety? Thank you.

Adrian Higgins: Thank you. Thank you. NBC wanted me to appear after the new Leno show, but my hair was the wrong color. A gardenia would work in Richmond, I would pick a hardy variety such as Kleim's Hardy or Chuck Hayes. For something a little different, I would try an edgeworthia, it would do beautifully in Richmond, or the Daphne Carol Mackie (Go with the edgeworthia).


Fairfax: Re: what nandina can tolerate: About half of ours were eaten alive by voles one winter; the (about two-yer-old) shrubs fell over, and we found virtually no roots or crowns left. Those that survived that winter seem okay.

Adrian Higgins: Voles are something else; they work underground. At least the deer make no subterfuge of it. You could plant the nandina with a gravel backfill that would thwart the voles.


Mclean, Va.: First, I am SO glad you are back for this chat! Gardening is a mystery to me and having you as a resource, Adrian, is so reassuring. So: I am dying for a Nagami Kumqat tree (mini/dwarf) this spring for my Eastish facing patio (mostly full sun in the morning). It will be in a large pot. I plan to winter it inside in a sunny spot. Does this sound like a reasonable plan? Can you help me avoid any pitfalls and/or suggest a reputable source? A lot of the Floridians won't ship out of state. Thank you!

Adrian Higgins: I've never grown kumquats. They are handsome plants and might be hardy here in a protected garden inside the Beltway. Might be good insurance though to have one in a pot to bring in. I would imagine Edible Landscaping in Afton, Va. would have them. If they don't, e-mail me and I'll find a source.


I am also about to enter the brave new world of tweets and twitters.: So we can ask you questions on line the way we do here? My Tuesdays, and my garden, have not been the same since you left us.

Adrian Higgins: Yes, to the extent that one can express oneself in 140 characters. I'm hoping to set it up in a way that I can answer gardening questions.


D.C.: Comment: When you mention plants that chatters may want to try, it would be great if you could include a link to a site with information, pictures of them, etc. Do you have some generally good sites that you could send us to? I just tried White Flower Farms for edgeworthia and found nothing.

Adrian Higgins: Good point. In an age of search engines, there are so many sources. I know Fairweather Gardens in N.J. sells them.


Annandale, Va.: Hi. I asked the question about vegetable gardening near a driveway. My main concern is car exhaust. They are both fairly new vehicles. Would that make a difference? Thanks.

Adrian Higgins: I would think the particulate might settle on the leafy greens, but I'd only be concerned if they were idling cars for many, many minutes. We don't have lead in gas anymore, which would have been more of a concern.


so glad you are back!: I live in the Gaithersburg area. Can you suggest a fig tree that would be okay in the winter? Thanks!!

Adrian Higgins: Thank you. G'burg is a bit on the colder side so you could safely pick a cold hardy variety such as Chicago, Brown Turkey or the yellow fruited Marseilles. (Go with the Marseilles). The knack to getting figs to work here is to plant them in sun but close to a sheltering hedge or wall (preferably on the north side of the plant). You also want to get their roots established for the first three years, that makes them hardier, so plant them in spring for good first year root development and give them a little protection (burlap) the first winter or two.


Anonymous: What kind of soil is best to use? I understand the need for starting soil, but what about an inch of that on top of a bottom of compost? Where do you find information about temperatures of plants that like to start in a cool greenhouse? Is it important to have a liquid food put in the water after the plants are about 3" high?

Adrian Higgins: Compost below the seed starting soil is a good idea. I wouldn't start seeds directly in compost, because it's not sterilized. You cannot start seeds in garden soil, top soil or even potting soil. You really need a seed starting mix, which you can make by blending peat moss (or coir) with perlite and perhaps some sand and vermiculite. Maybe I should do a column on seed starting mixes, or would that be too boring?


No room for greenhouse: As an apartment dweller, I am wondering if those counter-top, grow-light systems for herbs and small greens are worth it? Would love to have chives, etc. at my fingertips, and I have the counter space, but do you think it's too expensive or worthwhile? Or should I just plan my menus and grab what I need at the grocery store?

Adrian Higgins: You can spend a fortune on custom made growing tables with growing lights, but if you are handy, you can fabricate them using half inch pvc plumbers pipe or lumber or even re-purpose bookshelves. Once you have a multi layered stand, you can use cheap, four foot shop lights. They should hang on chains and be adjustable, so you can keep the lights six inches above the plants as the sprout and grow.


Takoma Park: I work for the EPA. I do a fair amount of work on greenhouse fumigants and such. If you want a nice yielding greenhouse, you need to sanitize the inside. You had the correct term. Bleach is the bare minimum one should be using.

There are other products as well (foggers and other fumigants), but please read and follow the directions on any and all pesticides (greenhouse sanitizers and the bugs) to THE LETTER. The wording on the labels is driven by the results of EPA mandated tests conducted on the product.

Adrian Higgins: Thanks, passing this along.


Saffron Crocus in Md.: I have an extensive herb garden that I adore. I also love tulips crocus and other bulbs. I am considering getting and planting saffron crocus for culinary use, as well as they are pretty. How well do they grow in Maryland? How much of a risk would this be in a Baltimore county herb garden?

Adrian Higgins: They grow well here and flower in the fall (Crocus sativa). The only difficulty is that you will need thousands of them to yield enough saffron to use. (Hence the price of saffron in the shops.) The deer might like them, as well.


Nags Head, N.C.: Do you know what sort of grass would do well in a dog run? We are fencing in an area at our beach house that currently is all sand to make a running and training area for our two dogs. I can't decide if we want to put in some sort of turf grass (with all the water and labor of mowing demanded) or artificial turf made to be pet-hardy (but very expensive for a large area). Any ideas?

Adrian Higgins: I think I would go with a decorative bermudagrass, where you are.


Greenhouses: In your list of greenhouses, do any of them offer "tours" specifically designed for children? If I wanted to bring four or five wee ones (ages 6 or so) on a field trip, would these places be able to help out with questions or demonstrations?

Adrian Higgins: No. I'd love for some of the enterprising, small greenhouse growers in the rural areas around Washington would band together to organize such a tour. I think it would be so enriching for the children. I know Green Spring Gardens in Alexandria hosts a lot of tours for grade schoolers that includes a visit to their small greenhouse. And of course, an increasing number of schools are building their own greenhouses.


Oakton, Va.: Are there plans or blueprints for the greenhouse you mention that Tom Karasek built? Also, are you suggesting that the Snap & Grow small hobby houses are not advisable? The one pictured in your article looks very sturdy.

Adrian Higgins: I'd say the Snap and Grow is fine, but go for one of the larger sizes and make sure that the polycarbonate is double walled. I think we've run out of time. Thank you so much for joining the discussion today.


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