Princeton University

Gardening Tips

New Jersey’s warm, humid summer weather makes gardening very easy. With a little time and attention, a garden plot at Lawrence will provide you with beautiful flowers and home-grown, organic vegetables that taste far better than grocery store varieties. (By tradition and by consensus, Lawrence gardeners practice organic gardening. Contact the garden coordinator with any questions.) You’ll also enjoy the community of gardeners, who can be seen out in the garden on warm summer evenings and weekends chatting and sharing gardening information. However, in the late summer when it’s hot and the weeds and bugs are taking over, gardening can also be a lot of work and sometimes discouraging. These are some tips designed to help you make the most of gardening at Lawrence. We also have an informal e-mail list of current gardeners. Feel free to e-mail this list if you have a gardening announcement or issue to discuss.

Choosing a plot

The garden is located behind buildings 6 and 14, and divided into about twenty plots. It is surrounded by a ten-foot fence to keep out the deer. A signup sheet is posted on the community room door (in building 14) each year in early spring. Gardeners continuing from previous years always have the first option to keep their plots. Before you sign up, you will want to go out to the garden to look at the plots you are considering–some will have fences and more recently cultivated soil from previous gardeners.

Shared Resources: Tools, Water, Mulch, Compost Many gardening basics are provided by the university or the Lawrence Community. Gardening tools such as shovels, hoes, rakes, hand trowels, and watering cans are kept in the toolshed just inside the garden gate, and are shared by all Lawrence gardeners. Two wheelbarrows and a large composter are also community property. We encourage you to contribute kitchen & garden scraps to the composter; see composting guidelines for more information. Piles of wood chips and leaf mold mulch are provided by the university and located just inside the garden’s main gate. The university provides three water hydrants; please use the garden hoses with care as they wear out easily and must be replaced by the Lawrence Community. Please practice good gardening citizenship: take care of common resources, return them to their proper places, and dispose of your trash. You can put small amounts of trash in the garbage can, and small weeds/plant scraps in the composter. Large amounts of garbage and weeds (and weeds with woody stalks) should be taken over to the dumpsters. Do not allow children to play with hoses, tools, etc. Please keep the garden gate closed to keep out the deer!

NOT provided are fencing, stakes, tomato cages, seeds, etc. However, some of these items are left behind by former Lawrence gardeners and can be claimed by whoever needs them. In general, items left against the fence near the composter are available for anyone’s use. If you’re not sure, please ask! If you have seeds or seedlings to share, let everyone know by e-mailing the garden list.

Soil Improvement

Although it’s heavy and clay-ey, our soil is quite good nutritionally, and many Lawrence gardeners have had success with many vegetable crops without any soil amendments. However, anything you can do to improve drainage (i.e. mixing in leaf mold or sand, or building raised beds) will probably help, especially for root crops like carrots, parsnips, and beets. Our soil is also slightly acidic, and many gardeners have used alkaline additives such as limestone (available at any garden center) to improve the pH balance of the soil. Amending with compost or mulch before you plant (see below) helps restore nutrients taken out by crops grown the year before, and for this reason it’s a good thing to do. Amending in the fall, after the remains of the year’s crops have been removed, is also a good idea. Crop rotation, planting different crops in each bed from year to year, helps even out the demands made on the soil, since each crop requires a different balance of nutrients–and some can even replenish nutrients needed by other plants. Beans and peas, for example, can improve nitrogen levels in the soil — an important nutrient needed by many other crops.

Compost and Mulch

Mulch, and small amounts of compost from our community composter, are available in the garden. Dig in some of the home-made compost as a nutrient boost when you plant a rose, or other heavy feeders like tomatoes and peppers. But please respect that this compost is a fairly scarce commodity and to be shared among all the gardeners. The leaf mold mulch is also useful as a compost (mix a wheelbarrowfull into a bed) to improve the soil; or as a top mulch near crops to keep soil from drying out, to protect plants from soil pathogens, and to keep down the growth of weeds. The leaf mold mulch contains some impurities (mostly metal litter, such as crushed soda cans and the occasional light bulb), but most of us have used it without any problems. Some gardeners prefer to buy other mulches like licorice bark (available at garden centers), as it looks nice and lasts longer than the leaf mold. The wood chips are useful for making paths and blocking the growth of strong weeds. Try to get your mulch down early in the season, before the weeds really take off (which they do, starting in mid-May).


Summers here can get very hot and dry, so be prepared to water your garden! How often you need to water depends on how much rain we’re getting. Put your fingers in the soil — if it’s dry an inch down, then it needs to be watered. If you notice your plants wilting, you’ve probably waited too long. It’s generally best to give plants a thorough watering once or twice a week rather than a little water every day. This way, the water soaks down deep and encourages your plants to grow deep roots — thereby becoming more drought resistant. On the other hand, some gardeners prefer to water more frequently during especially hot and dry spells. Mulch will help your soil retain moisture, and your plants withstand drought with less watering. Plants can also get over-saturated and die from too much water. This can be a problem particularly in low-lying areas of the garden when we have a long rainy spell. The clay-ey soil here makes this problem worse because it doesn’t drain well. To improve drainage, (especially in low-lying plots), it’s wise to build raised beds. Do NOT leave the hoses on overnight, and please try to conserve water! Also, be careful with the hoses; they spring leaks easily.


Anything you like to eat, rabbits, raccoons and groundhogs also like to eat. If you want to keep it for yourself, put up a fence. Chickenwire is most effective and least intrusive aesthetically. Green plastic fences don’t work too well for these critters (they can chew threw them). Be sure you either bury the fencing or flap it on the ground about 6-8″ to keep animals from digging underneath. Also, if the guage of the fence is too big, critters will walk right through. This is especially important in baby rabbit season (May/June)! The exterior fence put up by the builders is way too big a mesh to stop rabbit penetrations. The groundhogs have well-established holes underneath the fence, which generations of Lawrence gardeners have been unable to permanently block. Groundhogs can climb, too — and believe it or not they have been seen scaling the old ten-foot exterior fence! Some gardeners have had success with a low fence, (it may help to only grow things critters don’t like much, such as onions and herbs, near the fence so they aren’t tempted), but others have found it most effective to build a 5- or 6-foot fence, preferably with a floppy top to make it more difficult for the critters to scale. It seems that no kind of fence is effective in keeping out raccoons, who have been known to ravage an entire crop of sweet corn soon before the unsuspecting gardeners would have harvested it.


Beware of ticks (Small Deer Ticks may carry dreaded Lyme Disease; Large Dog Ticks may carry Rocky Mountain Spotted Fever). These are serious illnesses! Also watch out for poison ivy. Ticks and PI are common in parts of the garden. Groundhogs and rabbits are abundant. They love to eat most flowers; anything in the pea family including peanuts; all kinds of root crops and members of the carrot family including parsley. They don’t much like peppers, tomatoes, onions or most herbs. They don’t eat watermelon/pumpkin/squash leaves but they will go after immature fruit. Mice will attack small fruits especially when it’s really dry. Watch out, they love watermelons. See above (Fences) for tips on keeping out groundhogs and rabbits.

Slugs are also quite destructive, especially of leaf vegetables and low-growing ornamentals like pansies. They can be kept at bay by sprinkling a sharp ground-up substance, like eggshells or diatomaceous earth, around the plants most affected. If you use diatomaceous earth, you have to re-apply after every rain. (Be advised: do not use the type of diatomaceous earth that is used in pool filter systems, which is of a finer texture. This type is dangerous to lungs if inhaled. A garden supply store can help you identify which type is recommended for slug control.) The most troublesome insect pests for most Lawrence gardeners have are bean beetles, cucumber beetles, squash bugs, nematodes, flea beetles, cabbage worms, and squash vine borers. Scary plagues of Mexican bean beetles will devour bean plants. The adults look like yellow ladybugs, and they create thousands of disgusting little (1 cm) yellow spiky larvae that live on the underside of leaves. Cucumber beetles will infest cukes, watermelon and squash, decimating the leaves and spreading a wilt disease that will kill the plants. Squash bugs swarm on any kind of squash, melons, etc; planting them on trellises makes it easier to control these pests. Tiny nematode worms will go after some root crops like carrots and radishes, but might be discouraged by improved drainage. Flea beetles (as the name implies, tiny black beetles) will destroy eggplants.

Cabbage worms are inch-long worms the exact color of broccoli leaves, which hatch from eggs laid by the pretty little white moths you might see flying around the garden in early summer, and devour cabbage, broccoli, cauliflower, etc. Squash vine borers are particularly fond of zucchini and summer squash — they bore into the base of the vine, and before you know it the entire plant wilts and dies. There are various organic methods of controlling these pests.

Pest Control

You can try companion gardening techniques, which involve planting strong-smelling plants like onions or marigolds next to vulnerable crops as a pest deterrent, as well as planting flowers which attract predatory bugs (to eat the pests). You can get suggestions on companion gardening strategies from other gardeners, or check a book out of the library. Another method is to prevent the pests from reaching your plants, using barriers. Cover the most vulnerable crops, before the pests attack, with a lightweight light- and air-permeable cover (available at garden centers) that keeps out the bugs. The catch here is that some crops, like zucchini, need to be uncovered when they blossom to make fertilization possible. Other methods are hand-picking and organic sprays. The most important step here is vigilance: check your most vulnerable plants (squash, beans, cabbage family, etc), especially the undersides of the leaves, regularly especially in mid and late summer. Pick off and destroy any bad bugs or eggs that you see — ask other gardeners for help in pest identification; you don’t necessarily want to destroy all bugs because some are predators which eat the pests. As a last resort, once you have an infestation, you can try an “organic” insecticide such as pyrethrin (considered organic as it is derived from a plant and breaks down quickly), sabadilla dust, or hot pepper spray. Check the plants daily and spray or powder any bugs you see. Apply insecticide directly to the insect, rather than just sort of casting it about, in order to a) not waste it, b) not kill beneficial insects like ladybugs or praying mantises, c) not have chemicals around needlessly. The worst pests for ornamental plants in recent years at Lawrence have been Japanese beetles, as they eat roses. Our rose-growing expert, Emily, recommended killing these with pyrethrin or hot pepper spray early in the morning, when they are drowsy. Thrips are tiny insects that attack the buds of flowers, and can be controlled in the same way. You may occasionally come across white grubs in the soil. The smaller grubs, about an inch long, probably belong to Japanese beetle. They can be quite destructive to vegetable crops as well as roses and you’d be wise to destroy them. Larger grubs, about 2 inches long, are cicada larvae, and they are not too harmful.

Planting Recommendations


They don’t call New Jersey the “Garden State” for nothing! Given proper treatment, almost anything will grow here, and you can completely neglect your garden and still get results from some plants! We encourage you to be adventurous and try whatever plants catch your fancy. Current Lawrence gardeners recommend, as the easiest and most successful plants to grow here:

Leafy vegetables such as lettuce, spinach, swiss chard, kale, and any kind of salad greens do very well here. The main problem here is slugs, especially when the seedlings are young and when we’re having a very wet spell. Almost all these leafy greens are cool-weather crops, best planted in early to mid spring.

Peas and beans grow very successfully here. Peas are a wonderful spring crop — just rig up a trellis for them to climb, and they’ll grow fast. Try sweet peas for their beautiful flowers, or sugar snap peas to eat straight off the vine. (These have delicious edible pods, so you don’t need to shell them — less work and a bigger crop). Beans also grow very well, though as described above they’re susceptible to attack by Mexican bean beetles.

Anything in the onion family is brainless and problem-free, and might help deter pests on other crops grown close by. Clusters of chives have spread wild in various parts of the garden. Garlic bulbs can be planted in the spring or the fall. Buy sets of onions from a garden center in early spring, and you’ll be rewarded with a nice crop in the fall. Leeks are a bit more work, since they are more tender if you mound the soil up around the stems as they grow, but they too do very well in our soil.

Root vegetables including radishes, carrots, beets, and parsnips, are very easy to grow. For carrots, however, it’s especially important to heed the above advice about soil drainage — both to encourage the carrots to grow straight and long, and to discourage nematode worms.

Nightshades of every description do extremely well in our soil and climate. These include tomatoes, tomatillos, peppers, eggplant, and potatoes. More adventurous gardeners might want to try tobacco (flowering and smoking), datura, and the more bizarre nightshades like shoo-fly plant (Nicandra physaloides, similar to tomatillo), Solanum atropurpureum, naranjilla, and belladonna/deadly nightshade. Watch out, though — these all attract flea beetles, sometimes in astounding numbers.

Cabbage family crops, including broccoli, cauliflower, cabbage, brussels sprouts, etc, are more difficult to grow. They have a long growing season and must be started indoors in very early spring, or you can purchase seedlings from a garden center. Even then, they sometimes don’t mature before it gets too hot for them to thrive. And they can be devastated by attacks from groundhogs, rabbits, and especially cabbage worms. If you really want to try, broccoli has been the most successful of these crops in recent years. The leaf vegetables in this family: kale, bok choy, collard greens, etc, grow more quickly and seem to be more successful at Lawrence.

Curcubits — squash, pumpkins, melons, gourds all love the heat and humidity here. But with melons in particular, you really have to watch for bugs (see above), vine borers, and powdery mildew. If you can get through a season without being wiped out by any or all of these, you can get good crops, but it is NOT easy. Zucchini and summer squash are the easiest of these plants to grow. Though they’ll likely be destroyed midseason by the vine borers, you’ll probably get quite a few squash before that happens.

Corn is probably not a good crop to grow here. It grows very well, but it requires a LOT of water, a lot of sun and a lot of space for a relatively small yield that is invariably raided by the raccoons just as the ears start to get to a good size. Not to mention that corn is very plentiful at roadside stands in the summer.

Just about all herbs are virtually maintenance-free and grow beautifully in our garden. Perennial herbs like rosemary, thyme, lavender, mints, and oregano are best purchased as plants at a garden center — they are difficult to start from seed. Sage is also in this category, though it’s usually not a perennial in this climate, since it often can’t survive the winters. You’ll find several varieties of mint growing wild throughout the garden — these actually become very invasive, so if you want to plant mint you’d be advised to put it in a container and bury the container so it can’t spread. Annual herbs (basil, parsley, cilantro, dill, etc.) are easy to grow from seed, though parsley takes a long time to sprout. Plant parsley, cilantro, dill, and chamomile in the spring; wait until May to plant basil.

If you’re going to be here more than a year or two, try planting perennial fruits, vegetables, and ornamentals. Perennials make your garden less work-intensive because you don’t have to replant! Current gardeners have had success with strawberries, raspberries, and rhubarb. Other perennial vegetables like asparagus would also do well here, and provide a nice early spring crop with virtually no work once they’re established.


From seed, try sunflowers, zinnias, cosmos, marigold, nasturtium, Valerian, malva, heliotrope, poppies, salvias, phlox, sweet peas, calendula, cyoglossum (Chinese forget-me-not), and many more. Bulbs/tubers — lilies (oriental, Asiatic, turk’s-cap, day), cannas, daffodils, tulips, gladiolas, dahlias, fritillaria, peonies, clematis. Roses — This is a fabulous climate and soil for roses; our former resident rose enthusiast had over 100 plants of various sizes, some quite small… some not so small. You do have to monitor against fungal diseases like black spot and mildews, esp powdery. Emily recommends spraying 2 or 3 times a season with a copper/soap spray from Gardens Alive! which breaks down quickly in the soil.

Sources for seeds and plants

Locally, for plants and seeds: Obal Garden Center is right around the corner on Alexander Road. Also try Corner Copia in West Windsor. The Trenton Farmer’s Market is an excellent source for inexpensive seedlings, but the quality varies depending on the vendor. There are also several garden centers on Route 206 South. Mail order: We recommend Pine Tree Garden Seeds for all sorts of supplies — excellent quality and unbelievably cheap! Seeds of Change is an excellent source for heirloom varieties, organically grown. Parks seeds is also good. For fruits like berries etc. Edible Landscaping is fantastic. Also try Johnny’s, Cook’s Garden, Territorial, Totally Tomatoes; for flowers, Select Seeds; for oddball stuff, JL Hudson, Thompson & Morgan. For plants, try Richters Herbs in Canada, Heronswood Nursery, Greer Gardens, Roslyn Nursery, Plant Delights, Wayside, Logees Greenhouses, White Flower Farm, Forestfarm.