I took a look at some local weather history last night and it seems June 2015 has shattered local heat records and lack of rainfall records. So far, it has been an amazing summer for vegetable gardening at MCGA. The heat has produced a bumper crop of everything in our garden: cucumbers, beets, beans, peas, broccoli, lettuce and greens, cauliflower just to name a few. With all the continued heat, hopefully the PNW won’t be headed into the realm of enforced water restrictions this summer.
Plants are over 90% water. There are critical periods in which lack of water has an adverse effect on your vegetable crops. Some of these effects can be mitigated if you can target the timing and amount of water to add. As a rule of thumb, water is most critical during seed germination, the first few weeks of development, immediately after transplanting (try to fill your planting hole up with water before you put your transplants in and try not to plant or move crops in full sun), and during flowering and fruit production.
Cole crops (broccoli, cabbage, cauliflower, collards, Brussels sprouts, kale, and kohlrabi) need moisture during their entire life span. This is probably one of the most sensitive plant families when it comes to needing consistent watering. Water use is highest and most critical during head development, if consistent water is not given, the plant will be stunted, be very prone to aphid attack, the heads may not form or be very small and/or bolt and flower right away.
Beans have the highest water use of any common garden vegetable. During blossoming and fruit development, beans use one-quarter to over one-half inch of water per day. I plant my beans very densely so they can shade one another.
Lettuce and other leaf vegetables need water most critically during head (leaf) development. For quality produce, these crops require a constant supply of moisture. If not the greens can become bitter, stringy and they may bolt prematurely.
Onion family crops, (garlic, leeks) require consistent moisture and frequent irrigation due to their small, inefficient root system. They often fall over because to weak roots, it is best to pull them if this happens.
Potatoes tubers will be knobby if they become overly dry during tuber development. Potato scab is a common problem when there is insufficient moisture during tuber formation.
Tomato family (tomatoes, peppers, and eggplant) needs water most critically during flowering and fruiting. Blossom end rot (a black sunken area on the bottom of the fruit) is often a symptom of too much or too little water. Blossom drop is also a common problem that occurs from lack of water. The tomato family has a lower water requirement than many vegetables and plants are often over-watered in the typical home garden. Water your tomatoes very deeply; tomato roots can be as long as five feet or more.
Vine crops: cucumbers, summer and winter squash, and assorted melons need water most critically during flowering and fruiting. Vine crops use less water than many vegetables and are often over-watered in the typical home garden.
Watering wisely has always been a mantra at MCGA and more water wise garden solutions have been implemented throughout MCGA more than ever before. Hooray! The #1 way to increase your soil’s water holding capacity is to amend your garden soil with coarse, decomposed organic matter such as compost, leaf mold, manures, straw and more.
In our clay soil, organic matter glues the tiny soil particles together into larger particles, increasing pore space. This process takes place over time. This increases soil oxygen levels and improves soil drainage, which in turn increases the rooting depth allowing roots to reach a larger supply of water and nutrients. Another method to add organic matter is to replant the fall garden with a green manure crop such as winter rye or buckwheat.
I use mulches and drip irrigation to conserve water as well and to keep moisture off the foliage to avoid air borne fungal diseases.
Plant in blocks, rather than rows. This creates shade for roots and reduces evaporation. Shade cloth is helpful too.
Control weeds that compete with vegetables for water.
Group plants with similar water needs in the same section of the garden for easy irrigation. Cucumber, zucchinis, and squash, for example, require similar water applications.
Stay cool and let us know what techniques worked for you!